Barbara Claussmann
email: bclaussmann@slb.com

Julien Bailleul

Frank Chanier

Vincent Caron

Adam D Mcarthur

Geoffroy Mahieux

Corentin Chaptal

Bruno C Vendeville

Contrasting mixed siliciclastic-carbonate shelf-derived gravity-driven systems in compressional intra-slope basins (southern Hikurangi margin, New Zealand)

Keywords: active margin, confined slope channel system, mass-wasting system, mixed siliciclasticcarbonate systems, confined basins, trench-slope basins, thrust forelimb, thrust backlimb

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Understanding sediment transfer and distribution beyond the shelf edge and in the outboard part of continental margins has been at the heart of numerous studies in the past 60 years (e.g., [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF]; [START_REF] Posamentier | Eustatic Controls on Clastic Deposition II-Sequence and Systems Tract Models[END_REF][START_REF] Richards | Submarine-fan systems i: characterization and stratigraphic prediction[END_REF][START_REF] Posamentier | Seismic geomorphology and stratigraphy of depositional elements in deep-water settings[END_REF][START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF];

Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum

Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021. 105252 Here, we investigate the type and distribution of shelf-derived sediments, sourced from mixed siliciclasticcarbonate systems (i.e., compositional systems (sensu [START_REF] Chiarella | Types of mixing and heterogeneities in siliciclastic-carbonate sediments[END_REF]) that developed above the asymmetrical basin-bounding structures (e.g. thrusts and or fault-growing folds) of an actively deforming, confined intra-slope basin. We examine the vertical and lateral stratigraphic variability of the shelf-derived gravity-driven deposits, at outcrop-scale, from the Whareama trench-slope basin, in the emerged southern portion of the Hikurangi subduction margin, North Island of New Zealand. The deposits are of Middle Miocene age and incorporate similar material (nature and size of the clasts), albeit transported through a variety of sediment gravity flows, thereby suggesting different source, delivery and geotectonic settings across the same confined intra-slope basin.

Our study aims to determine how variations in the structural style (thrust forelimb and backlimb) and tectonic activity (renewal or quiescence) influence the generation of contrasting mixed siliciclasticcarbonate shelf-derived gravity-driven systems and deposits across a confined, intra-slope basin (e.g., trench-slope basin).

Specific objectives are to:

• Document the nature, architecture, and size of the different styles of shelf-derived sedimentation that can occur in a confined intra-slope basin, through an integrated interpretation of photogrammetry, fieldwork and taphonomic data.

• Gain new understandings on the controls on sediment transfer and distribution beyond the edges of mixed siliciclastic-carbonate shelves located upon and around the forelimb and backlimb of actively growing asymmetrical structures.

• Develop generic depositional models of the distribution and styles of shelf-derived systems and subsequent deposits in tectonically active settings.

• Determine the implications for the stratigraphic prediction of deep-marine, shelf-derived gravitydriven systems and, of shelf-derived mass-wasting systems along active margins.

GEOLOGICAL SETTING

Regional setting

The study area is located on the eastern North Island of New Zealand, on the tectonically active Hikurangi Margin (Figure 1). The Hikurangi subduction wedge (sensu [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF] Plate [START_REF] Ballance | Evolution of the Upper Cenozoic Magmatic Arc and plate boundary in northern New Zealand[END_REF][START_REF] Spörli | New Zealand and Oblique-Slip Margins: Tectonic Development up to and during the Cainozoic[END_REF][START_REF] Pettinga | Upper Cenozoic structural history, coastal Southern Hawke's Bay, New Zealand[END_REF][START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF][START_REF] Field | Cretaceous-Cenozoic geology and petroleum systems of the East Coast region[END_REF][START_REF] Nicol | Tectonic evolution of the active Hikurangi subduction margin, New Zealand, since the Oligocene[END_REF]. Bounded by the Hikurangi Trench to the east and the Forearc Basin to the west, the Hikurangi subduction wedge comprises a succession of elongated trench-parallel sedimentary basins (i.e., trenchslope basins) separated by tectonically active structural ridges [START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF][START_REF] Lewis | The emerging, imbricate frontal wedge of the Hikurangi margin[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF]McArthur et al. 2019).

Since the onset of subduction, the Hikurangi subduction wedge underwent a polyphase tectonic history, comprising three main tectonic periods (Figure 2 and references within). Complex stratigraphic architectures and geometries, such as diachronous sedimentation patterns, syn-sedimentary deformations and discontinuities, are characteristic of the Miocene-to-Recent trench-slope basin fills and attest of the close interplay between tectonics and sedimentation [START_REF] Neef | Geology of the Akitio area (1:50 000 metric sheet U25BD, east), northeastern Wairarapa, New Zealand[END_REF][START_REF] Neef | Neogene development of the onland part of the forearc in northern Wairarapa, North Island, New Zealand: A synthesis[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Burgreen | Evolution of a deep-water lobe system in the Neogene trenchslope setting of the East Coast Basin, New Zealand: Lobe stratigraphy and architecture in a weakly confined basin configuration[END_REF]McArthur et al. 2019;[START_REF] Mcarthur | Deformation-sedimentation feedback and the development of anomalously thick aggradational turbidite lobes: subsurface and outcrop examples from the Hikurangi Margin, New Zealand[END_REF]. Deepmarine sedimentation dominates their fill and includes mass-transport deposits (MTDs), turbidites and extensive hemipelagic mudstones; yet carbonate, biogenic and shallow-marine fringe deposits can also be found sporadically (Figure 2) [START_REF] Field | Cretaceous-Cenozoic geology and petroleum systems of the East Coast region[END_REF][START_REF] Lee | Geology of the Wairarapa area[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bland | Pegasus Basin, eastern New Zealand: A stratigraphic record of subsidence and subduction, ancient and modern[END_REF]McArthur and McCaffrey 2019). These basin fills either conformably or unconformably overlie the Cretaceous to Paleogene pre-subduction basement, mainly composed of the Lower Cretaceous Torlesse greywackes and the Upper Cretaceous to Oligocene detrital to pelagic series [START_REF] Spörli | New Zealand and Oblique-Slip Margins: Tectonic Development up to and during the Cainozoic[END_REF][START_REF] Bradshaw | Cretaceous geotectonic patterns in the New Zealand Region[END_REF][START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF][START_REF] Field | Cretaceous-Cenozoic geology and petroleum systems of the East Coast region[END_REF][START_REF] Lee | Geology of the Wairarapa area[END_REF].

Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252 Figure 1: (A): Major subduction-related morphostructural features of the active Hikurangi Margin, north Island of New Zealand. Black arrows show present-day relative plate motion between Pacific and Australian Plates from [START_REF] Beavan | Bivalve taphonomy in tropical mixed siliciclasticcarbonate settings. I. Environmental variation in shell condition[END_REF]. (AB -Akitio Basin; TwB -Te Wharau Basin). See (B) for the a -b general cross-section of the Hikurangi subduction complex (C.R -Coastal Ranges). Modified after [START_REF] Chanier | Extensional deformation across an active margin, relations with subsidence, uplift, and rotations: The Hikurangi subduction[END_REF], [START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF] and [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF].

Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum

Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

Southern Coastal Ranges

The study area lies within the exhumed inner portion of the subduction wedge (e.g., emergent trenchslope break) that forms the southern Coastal Ranges of the eastern North Island of New Zealand. Here, we focus on the tectonic settings at the end of the first compressional phase (Figure 2; Middle Miocene, Clifdenian -Lillburnian (Langhian to early Serravallian, 15.9 -13.05 Ma)), where both the inception and development of the trench-slope basins occurred [START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Malie | Spatial distribution and tectonic framework of fossil tubular concretions as onshore analogues of cold seep plumbing systems, North Island of New Zealand[END_REF].

During this time period, compressional tectonics resulted in uplift of some of the fold and thrust basinbounding structures and more generally of the margin [START_REF] Crundwell | Neogene stratigraphy and geological history of the Wainuioru Valley[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF]). The induced changes in depositional environments (e.g., neritic conditions) atop the structures controlled the development of shelfal environments, and, in particular, mixed siliciclastic-carbonate systems (i.e., compositional systems (sensu [START_REF] Chiarella | Types of mixing and heterogeneities in siliciclastic-carbonate sediments[END_REF]) at shallower waters whilst gravity-systems dominated elsewhere at deeper waters [START_REF] Crundwell | Neogene stratigraphy and geological history of the Wainuioru Valley[END_REF][START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF][START_REF] Neef | Geology of the Akitio area (1:50 000 metric sheet U25BD, east), northeastern Wairarapa, New Zealand[END_REF][START_REF] Lee | Geology of the Wairarapa area[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF]McArthur et al. 2019;McArthur and McCaffrey 2019;[START_REF] Crisóstomo-Figueroa | A new modelling approach to sediment bypass prediction applied to the East Coast Basin, New Zealand[END_REF][START_REF] Mcarthur | Deformation-sedimentation feedback and the development of anomalously thick aggradational turbidite lobes: subsurface and outcrop examples from the Hikurangi Margin, New Zealand[END_REF].

Numerous mixed siliciclastic-carbonate systems co-existing during this period formed a regional shelf domain throughout the south-western portion of Hikurangi Margin [START_REF] Crundwell | Neogene stratigraphy and geological history of the Wainuioru Valley[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF][START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF]. The shelves developed above substantially different substrata inherited from local tectonics, and they either unconformably overlie Lower to Middle Miocene syn-subduction sedimentary rocks or Cretaceous to Paleogene pre-subduction basement. Their depositional settings preferentially suggest narrow, continent-attached shelfal systems receiving regular terrigenous inputs from the hinterland [START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF][START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF]). However, isolated, continent-detached platform systems may also have locally occurred on some of the actively growing structures (see [START_REF] Caron | Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand[END_REF][START_REF] Caron | Episodes of seabed rise and rapid drowning controlling the development of regressive and transgressive rhodolithic limestones in a tectonically-active subduction setting (Early Miocene, Wairarapa region, New Zealand)[END_REF] for examples along the same margin, yet at different geological times). rework a substantial amount of shelf-derived material, incorporating sediments and fossils from neritic shelfal environments. Several occurrences of such shelf-derived mass-wasting events and related deposits of Middle Miocene age were identified in the southern Coastal Ranges cropping out across several trench-slope basins (i.e., Whareama, Te Wharau and Akitio Basins) (Figure 1; Figure 2; Figure 3). (2021). Lithostratigraphy details adapted from [START_REF] Chanier | Discovery of Pithonellids in the Upper Cretaceous of New Zealand; biogeographic, stratigraphic and tectonic consequences[END_REF], [START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF], [START_REF] Field | Cretaceous-Cenozoic geology and petroleum systems of the East Coast region[END_REF], [START_REF] Lee | Geology of the Wairarapa area[END_REF] and [START_REF] Bland | Pegasus Basin, eastern New Zealand: A stratigraphic record of subsidence and subduction, ancient and modern[END_REF] and detailing the pre-and syn-Hikurangi subduction series. Regional tectonism adapted from [START_REF] Chanier | Extensional deformation across an active margin, relations with subsidence, uplift, and rotations: The Hikurangi subduction[END_REF], [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF] and [START_REF] Malie | Spatial distribution and tectonic framework of fossil tubular concretions as onshore analogues of cold seep plumbing systems, North Island of New Zealand[END_REF]. New Zealand stages after [START_REF] Raine | New Zealand Geological Timescale NZGT 2015/1[END_REF] showing the equivalence with the international stages.

The Whareama Basin

The Whareama Basin is narrow (two to six kilometers wide), elongated (50 kilometers long) and trenchparallel (NE-SW) [START_REF] Johnston | Geology of the Tinui-Awatoitoi district[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF]. It is bounded by pre-Miocene basement ridges that are controlled by the Adams-Tinui Fault complex and Pukeroro Fault to the west (i.e, landward basin margins,

Figure 3) and the Flat Point-Whakataki Fault complex to the east (i.e, seaward basin margin, Figure 3).

The basin's development began at the onset of subduction and thus records gravity-driven deposits dating from the earlymost Miocene. It formed on the back of the Glenburn Nappe, a trenchwardadvancing thrust sheet composed of Cretaceous to Eocene pre-subduction series that are either unconformably or conformably overlain by syn-subduction deposits [START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF].

The study area is located on the eastern limb of the Whareama Basin, with beds strongly dipping towards the west (ca. 40°). Nearby, well-exposed Middle Miocene shelf-derived MTDs were previously described and attributed to result from the collapses of coevally developing narrow, continent-attached shelfmargins located to the north-west (Figure 3; Sefton Hills s-1 and s-2 sections) [START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF]).

DATA AND METHODS

This outcrop-based study integrates traditional and digital field data acquired during three field campaigns (2018,2019,2020) in the southern portion of the Hikurangi subduction wedge (Coastal Ranges, eastern North Island of New Zealand), and focuses on the shelf-derived gravity-driven deposits of the Waikaraka and Homewood localities (Figure 3; wk and hw sections).

Fieldwork consisted of logging sedimentological profiles (total of 312 meters at 1:50 bed-scale), measuring structural (e.g., ductile deformation analysis) and stratigraphic features (e.g., bedding, paleocurrent) as well as describing each shelf-derived flow deposit in a standardized manner (facies and geometries).

Owing to the abundant macrofossils contained in the deposits, occurring both as whole skeletons and fragmented remains, five taphonomic analyses were performed on approximately one square meter areas for both the outcrops (i.e., four at Waikaraka and one at Homewood). These analyses were restricted to the coarsest fraction (larger than five millimeters) of death assemblages contained in the deposits. Three categories of skeleton damages, namely fragmentation, abrasion and bioerosion, were described visually using the graded classification scale presented in Appendix 1, complemented by Caron (2011) and [START_REF] Caron | A new analytical procedure to graphically characterize the taphonomic properties of skeletal carbonates. An example from Miocene limestones of new zealand[END_REF]. outcrop models were then created in the form of high-resolution triangulated mesh textured with the photographs.

FACIES AND ARCHITECTURAL ELEMENTS

Facies and architectural schemes

Integration of the data allowed an analysis and comparison of the stratigraphic architectures and facies organization within both outcrops.

A total of 14 lithofacies were recognized across the two outcrops (summarized in Table 1 and illustrated in Figure 4, Figure 5, Figure 6 and Figure 7) and classified according to their dominant lithology, primary sedimentary features and interpreted in terms of flow processes using models from [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF][START_REF] Nardin | A review of mass movement processes, sediment and acoustic characteristics, and contrasts in slope and base-of-slope systems versus canyon-fan-basin floor systems[END_REF][START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF][START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF][START_REF] Kneller | Beyond the turbidite paradigm: physical models for deposition of turbidites and their implications for reservoir prediction[END_REF][START_REF] Mulder | The physical character of subaqueous sedimentary density flows and their deposits[END_REF]. Table 1: Lithofacies encountered at the Waikaraka (WKS) and Homewood (HMD) outcrops. See Figure 4 and Figure 5for representative photographs of each lithofacies at Waikaraka; and Figure 6 and Figure 7at Homewood. Note that the 'Classification' column refers to [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF] and [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF], and that extraformational clasts include pre-and syn-subduction lithoclasts, and syn-subduction bioclasts. Intraformational clasts include syn-subduction lithoclasts. They were then grouped into three main facies associations, which are related to main depositional systems (Fa1g, Fa2c, Fa3p) (Figure 8; Figure 9). The nomenclature we adopted follows the one defined by [START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF], [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF] depositional lobe settings, Fa2c to confined slope channel settings and Fa3p to shelf-derived masswasting systems.

Each facies association is described and interpreted in sequence below, directly in context of the outcrop where they were recorded. Figure 10, Figure 11 and Figure 12 illustrate the geometric relationships that exist between the different lithofacies and their associations as well as some of the sedimentary structures at different scales. The nature of the extra-and intraformational clasts reworked in the conglomeratic and coarse sandstone intervals is described separately (see Section 6) and summarized in Figure 13 and Figure 14.

Confined slope system

The Waikaraka section crops out five kilometers south of the Uruti Point and extends across one kilometer along the coast (Figure 3). Deposition occurred in the Middle Miocene, Lillburnian to Waiauan (Late Langhian to Serravallian, 15.1 -11.63 Ma, Appendix 2) and features the Fa2c depositional system, which can be divided into two main depositional units (Fa2c-e, Fa2c-l), hereafter described and interpreted in sequence. These units are bounded by major erosion surfaces. These prominent surfaces can laterally be traced over several hundreds of meters (>600 meters), exhibit a relief of up to two meters, and characteristically separate contrasting depositional facies (Figure 8).

Confined slope channel: axis to off-axis, early-stage fills (Fa2c-e)

Observations

Fa2c-e is characterized by crude fining-and thinning-upward series, dominated by coarse-grained facies.

Here, this association crops out over more than 600 meters laterally and is generally between 10 to 50 meters in thickness (Figure 8).

Fa2c-e mostly comprises amalgamated, very thick-bedded (one to >two meters), disorganized (CF) to organized (gHDTC), polymict and clast-supported conglomerates (Figure 4; Figure 10l; Figure 11; Table 1). The conglomerates commonly form continuous, broadly lenticular and fairly symmetrical bodies with low-relief erosional bases, thereby indicating a cross-sectional, rather than longitudinal, view of them.

Their upper topographies are uneven and they are occasionally overlain by thin-to thick-bedded, structured or structureless sandstones (SST), themselves often incised by the overlying conglomerates, thus forming composite conglomeratic bodies (Figure 4; Figure 8; Figure 11; 4; Figure 8; Figure 11; Table 1).

The conglomerates are generally overlain by series of laterally continuous, mostly medium-to finegrained, thin-to very thick-bedded sandstones, which are either amalgamated or capped by bioturbated mudstones (HDTC to LDTC) (Figure 5; Figure 8; Figure 11j; Table 1). The thicker beds show frequent grain-size breaks, indicating bed amalgamation (HDTC to LDTC-b). Their basal, coarser intervals are discontinuous, erosive and typically composed of gravel material similar to that of the conglomerates, which occasionally includes aligned mud clasts, plant debris and some shell fragments (Figure 5, LDTCb). The sandstones frequently contain soft-sediment deformation features (e.g., flame, load) in their structured intervals (Figure 10k), whereas, the mudstone caps, where present, commonly include Phycosiphon sp. and Chondrites sp. bioturbations.

Four occurrences of Fa2c-e were observed at Waikaraka (Figure 8; Figure 11).

The first occurrence is exposed at the base of the outcrop. Its basal surface is not visible as it lies below the sea level. The conglomerates are disorganized (CF) (Figure 8; Figure 4; Figure 11) with an average clast size ranging from granule-and pebble-grades, to pebble-and cobble-grades toward the southward wavecut platform. Boulders and outsized clasts (deci-to decametric) are frequent (Figure 10l), particularly to the south and in the disorganized intervals (CF). Sub-rounded clasts dominate, but, sub-angular clasts are common and sometimes restricted to specific intervals (Figure 4; see Section 6). The overlying sandstone-rich series generally fine and thin-upward, evolving from thick-to medium-bedded, concaveup sandstones pinching out to the north into nearly-flat bottomed, thinner-bedded sandstones with very thin-to thin-bedded mudstone caps (HDTC to LDTC) (Figure 8; Figure 10j, k; Figure 11). To the south, amalgamation dominates throughout (Figure 10i; Figure 11). This first occurrence ends with a couple of laterally continuous, very thick-to medium-bedded sandstones (LDTC-b) that are overlain by few thinnerbedded intervals (LDTC-a) and characteristically comprise large-scale fluid escape and soft-sediment deformation features (Figure 10j,k).

The second occurrence directly overlies the first, separated by a basal surface that varies from being sharp to erosional (> two meters incision) to the south (Figure 8; Figure 10i; Figure 11). The associated conglomerates are organized (gHDTC), mostly showing normally-graded patterns, amalgamated (i.e., no capping sandstone) and smaller (~one to one and a half meters thick) (Figure 8; Figure 4; Figure 11). -l). The letters refer to remarkable architectural elements that characterize the Waikaraka system: a detailed view and explanation of each of them is available in Figure 10. The colors used in the stereoplots correspond to the location circles presented on the outcrop model (top). Stereoplots (Schmidt, lower hemisphere) highlight the paleocurrents taken in the turbidite system after back-tilting of bedding planes to initial horizontal position (assuming cylindrical folding).

Figure 9: (A): 3D outcrop model (top) and interpretation (bottom) of the Homewood coastal outcrop. This outcrop exposes three distinct gravity-driven systems, from the bottom to the top, a slope channel system (Fa2c), a shelf-derived mass-wasting system (Fa3p) and a distal depositional lobe system (Fa1g). The letters refer to remarkable architectural elements that characterize the Homewood system: a detailed view and explanation of each of them is available in Figure 12. The colors used in the stereoplots correspond to the location circles presented in the outcrop model (top). Stereoplots (Schmidt, lower hemisphere) highlight the paleocurrents taken in the turbidite system (Fa1g, in green) and the fold axis of the slump-related folds taken in the mass-wasting system (Fa3p, in purple) after back-tilting of bedding planes to initial horizontal position (assuming cylindrical folding). The blue numbers U1 to U6 highlights six units, corresponding to six distinct episodes of mass wasting. (B): Sedimentary section 01 (SS-01) recorded at Homewood. This section provides an overview of the three facies associations encountered. The deposits are moderately-sorted and in average comprise sub-rounded granule-to pebble-grade clasts with a few scattered boulders and outsized clasts (Figure 4; see Section 6). To the north, these conglomerates are matrix-supported (Figure 8) and locally include a very thin, clast-supported basal layer (sheared DF) (Figure 4). The overlying sandstones characteristically present well-developed, southwardoriented soft-sediment deformation features in their structured intervals and their beds are frequently contorted, presenting apparent southward-verging recumbent folds (Figure 8). To the south, these folds appear to eventually evolve into matrix-supported conglomerates containing both folded sandstones and extraformational pebble-grade clasts (SL-a to DF) (Figure 8; Figure 11).

Finally, the third occurrence is present toward the top of the Waikaraka outcrop and alternatively comprises disorganized (CF) and organized (gHDTC) conglomerates, sometimes overlain by structured to structureless sandstones (SST) (Figure 8; Figure 10e; Figure 11). The deposits are generally moderately sorted and, on average, comprise sub-rounded pebble-to cobble-grade clasts (Figure 4; see Section 6), although some occurrences carry boulders and outsized clasts (Figure 10e). The overlying sandstone series is only a few meters thick, interrupted by another couple of meter-thick conglomeratic episode (fourth occurrence), itself characterized by a sharp upper surface (Figure 10a).

Interpretations

Fa2c-e is interpreted to characterize the axis to off-axis, early-stage (Stage I of [START_REF] Kneller | Architecture, process, and environmental diversity in a late cretaceous slope channel system[END_REF]) fills of confined slope channel complexes (sensu [START_REF] Sprague | Integrated slope channel depositional models: the key to successful prediction of reservoir presence and quality in Offshore West Africa[END_REF].

Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum

Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

The laterally extensive, coarse-grained and clast-supported conglomerates at its base represent deposition from gravelly gravity flows (Lowe 1982, R1, R2, R3 divisions). Upslope failures may have triggered all or part of these flows, which then began to transform from cohesive to cohesionless debris flows downslope [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF][START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF][START_REF] Sohn | Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)[END_REF]. Their abundant amalgamation surfaces, clast-supported textures (e.g., disorganized, inverse, normal) and very coarse grain sizes indicate significant bed load transport and rapid deposition of the gravels underneath gravelly high-density turbidity currents in an environment dominated by high-energy flows, erosion and bypass [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF].

The abundant scoured bases, combined with the other textural and sedimentary features suggest that these flows were funneled through low sinuosity, braid-like channels, as recurrently found in base of confined slope channel complexes (e.g., [START_REF] Galloway | Siliciclastic Slope and Base-of-Slope Depositional Systems: Component Facies, Stratigraphic Architecture, and Classification[END_REF][START_REF] Celma | Sedimentology, architecture, and sequence stratigraphy of coarse-grained, submarine canyon fills from the Pleistocene (Gelasian-Calabrian) of the Peri-Adriatic basin, central Italy[END_REF][START_REF] Gamberi | Integrating modern seafloor and outcrop data in the analysis of slope channel architecture and fill[END_REF][START_REF] Li | Architectural and facies organisation of slope channel fills: Upper Cretaceous Rosario Formation, Baja California, Mexico[END_REF]McArthur and McCaffrey 2019;[START_REF] Kneller | Architecture, process, and environmental diversity in a late cretaceous slope channel system[END_REF]. The southward increase in clast size observed in the first occurrence suggests a southward evolution from off-axis to axis settings [START_REF] Campion | Outcrop Expression of Confined Channel Complexes[END_REF].

The general upward internal organization observed in the conglomerates and the overlying sandstone series likely resulted from gravelly to sandy high-to low-density turbidity currents from multiple, rather than single flows [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF], with flows initiating from a shallow marine environment connected to a vegetated hinterland sourcing the abundant terrigenous material (Kuenen 1964). The resulting deposits suggest lower energy environments leading to both the progressive abandonment of the channel system and passive infilling of the relief [START_REF] Galloway | Siliciclastic Slope and Base-of-Slope Depositional Systems: Component Facies, Stratigraphic Architecture, and Classification[END_REF][START_REF] Mchargue | Architecture of turbidite channel systems on the continental slope: Patterns and predictions[END_REF]. Axis to off-axis abandonment facies are typically sand-rich, fairly thick (e.g., medium-bedded) and highly to moderately amalgamated [START_REF] Campion | Outcrop Expression of Confined Channel Complexes[END_REF][START_REF] Mchargue | Architecture of turbidite channel systems on the continental slope: Patterns and predictions[END_REF][START_REF] Hubbard | Sediment transfer and deposition in slope channels: Deciphering the record of enigmatic deep-sea processes from outcrop[END_REF].

As previously described, four distinct occurrences of these axis to off-axis, early-stage fills were observed at Waikaraka, thereby indicating the presence of several slope channel complexes infilling one larger channel conduit (sensu [START_REF] Sprague | Integrated slope channel depositional models: the key to successful prediction of reservoir presence and quality in Offshore West Africa[END_REF]). However, Fa2c-e only provides information on the deposits that form the lower part of these channel complexes.

The textural changes observed in the second occurrence here suggest transformation from cohesive to cohesionless flows, resulting from progressive dilution of a parental debris flow (DF) evolving into a highconcentration gravelly dispersion overlain by a lower-concentrated and turbulent suspension (gHDTC) (Sohn et al. 2002, i.e., bipartite or stratified flows). When taken in consideration with the recurrent softsediment deformations, these elements suggest that this second occurrence may originate from several, small-scale failure events, either at or near the shelf break, or directly from the channel walls [START_REF] Celma | Sedimentology, architecture, and sequence stratigraphy of coarse-grained, submarine canyon fills from the Pleistocene (Gelasian-Calabrian) of the Peri-Adriatic basin, central Italy[END_REF][START_REF] Janocko | The diversity of deep-water sinuous channel belts and slope valley-fill complexes[END_REF][START_REF] Janocko | Architecture of coarse-grained gravity flow deposits in a structurally confined submarine canyon (late Eocene Tokaren Conglomerate, Slovakia)[END_REF]. deposited in the channel conduit and the southward component observed in the above features indicate a potential northward location of the source region. Whether it is regional or local is here a matter of speculation. The large-scale fluid escape structures present in the underlying sandstones would result from sudden loading of the mass-wasting products onto the sandstone strata, increasing pore pressure and promoting dewatering (Figure 10k) [START_REF] Browne | The role of mass transport deposits contributing to fluid escape: Neogene outcrop and seismic examples from north Taranaki, New Zealand[END_REF].

Despite the changes observed in the second occurrence's texture and clasts (see Section 6.3), the absence of shutdown mud drape, the only weakly erosional basal surface separating the first and second occurrences, and their general crude fining-and thinning-upward trend all suggest that these two occurrences belonged to the same channel complex, rather than two distinct complexes [START_REF] Kneller | Architecture, process, and environmental diversity in a late cretaceous slope channel system[END_REF]. The same reasoning applied to the third and fourth occurrences allows considering that these two belonged to another confined channel complex.

Overall, the lateral and vertical facies evolution observed throughout Fa2c-e suggests a general evolution from off-axis to axis settings towards the south. Notwithstanding the overall outcrop conditions (no 3D control) and or the orientation of the outcrop to withhold their exposures, the absence of recognizable lateral-accretion packages (LAPs) (sensu [START_REF] Abreu | Lateral accretion packages (LAPs): an important reservoir element in deep water sinuous channels[END_REF]) may also inform that the slope channel system (Fa2c) was likely low to moderately sinuous and generally erosional. Such channel belts usually occur in the upper-to middle-parts of the continental slope [START_REF] Janocko | The diversity of deep-water sinuous channel belts and slope valley-fill complexes[END_REF]. Finally, the micropaleontological analyses suggest that deposition took place at outer bathyal paleodepths (Appendix 2).

Confined slope channel: axis to off-axis, late-stage fills (Fa2c-l)

Observations

Fa2c-l presents contrasting sedimentary facies and architectural styles to those of the underlying Fa2ce, characteristically comprising fining-and thinning-upward series, dominated by fine-grained facies, only punctuated by coarser intervals. This association is traceable across the entire outcrop laterally (>900 meters) and can hold over 40 meters in thickness. Each storey commonly starts with amalgamated, thick-to very thick-bedded (one to one and a half meters), organized, polymict and clast-supported conglomerates (gHDTC) deposited above a broadly erosional, concave-up base (Figure 4; Figure 11). These are overlain by a fining-and thinning-upward conglomerate to sandstone series, capped by bioturbated mudstones (gsHDTC), which is, in turn, overlain by another fining-and thinning-upward series of nearly-flat bottomed, thick-to thin-bedded sandstones and mudstones (HDTC to LDTC) (Figure 5; Figure 10b, h; Figure 11). The basal conglomerate to sandstone series shows repeated bed amalgamation, thus forming composite stratigraphic infills (Figure 10f; Figure 11). Conglomerates are concentrated within the basal intervals;

sandstones quickly become dominant, generally representing a third of the channel storey fill (Figure 8;

Figure 11). The conglomeratic intervals are broadly lenticular, laterally pinching out, amalgamated and often include clast imbrications and subtle cross-stratifications (Figure 10c, f, h). Interestingly, their matrix seems primarily made of bioclast content (e.g., shell fragments) toward the top of Fa2c-l.

The bases of the conglomerates commonly display centi-to decametric soft-sediment deformation structures (e.g., flames) and large sole marks (e.g., flutes) (Figure 5; Figure 10d,g). Boulders and outsized clasts usually mark the transition from the inverse-to normally-graded patterns, and their proportion generally increases toward the south (Figure 5, gsHDTC to HDTC). Clasts are sometimes of larger size than the conglomerate bed itself, thus protruding into the overlying sandstones (Figure 5, gsHDTC to HDTC). On average, sub-rounded pebble-grade clasts dominate. In Fa2c-l, the HDTC sandstones that directly overlie the conglomerates are commonly coarse-grained in their traction intervals, show trough cross-stratifications and include plant debris, numerous shell fragments (Figure 10g) and abundant aligned mud clasts at their base. These sandstones form broadly lenticular bodies, with locally erosive bases characterized by very coarse-to coarse-grained material (Figure 10a, f). They eventually reach medium-to fine-grain sizes in the remaining intervals and in the subsequent fining-and thinning-upward series (HDTC to LDTC). The paleocurrents measured in the sandstone intervals indicate a general southward trend (Figure 8), which is consistent with measurements from imbrications within the coarse-grained basal fills.

Two occurrences of Fa2c-l were observed at Waikaraka (Figure 8; Figure 11).

The first occurrence corresponds to the above description. It is about 40 meters thick and comprises eight channel storeys (sensu [START_REF] Sprague | Integrated slope channel depositional models: the key to successful prediction of reservoir presence and quality in Offshore West Africa[END_REF]. Its basal surface is sharp, concave-up and broadly incises

Fa2c-e with up to 2 meters relief (Figure 8). The second occurrence is observed at the top of the quaternary beach deposits after that. Its basal surface is sharp above the underlying Fa2c-e occurrence and it is only comprised of sandstones (HDTC to LDTC) (Figure 10a, e; Figure 11).

Interpretations

Fa2c-l is interpreted to represent the axis to off-axis, late-stage (Stage II of [START_REF] Kneller | Architecture, process, and environmental diversity in a late cretaceous slope channel system[END_REF]) fills of confined slope channel complexes (sensu [START_REF] Sprague | Integrated slope channel depositional models: the key to successful prediction of reservoir presence and quality in Offshore West Africa[END_REF]. Characterized by multiple episodes of erosional bypass and sedimentation, these form the middle fills of channel complexes.

The conglomerate-to sandstone-dominated basal successions (gHDTC and gsHDTC) that broadly fill the erosion surface result from stratified gravelly gravity flows that are confined within channels [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF][START_REF] Campion | Outcrop Expression of Confined Channel Complexes[END_REF][START_REF] Sohn | Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)[END_REF]. The basal dewatering features suggest rapid deposition and loading of the channel fills, whereas the frequent amalgamation observed in both the conglomerates and sandstones implies that erosion and bypass were dominant in the basal interval [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF].

Transport of large (e.g., outsized) clasts can be explained by flow confinements such as the ones found in confined slope channels, where the flow size, velocity and carrying capacity are maximized [START_REF] Postma | Large floating clasts in turbidites: a mechanism for their emplacement[END_REF]). The high degree of preservation of mud clasts in both the conglomerates and overlying sandstones, scattered as lag material indicates high fall-out rates [START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF]), whereas the increase in content of coarse and fine skeletal fraction toward the top of the series rather suggest deposition of calciturbidites (e.g., [START_REF] Haak | Compositional variations in calciturbidites due to sea-level fluctuations, late Quaternary, Bahamas[END_REF][START_REF] Reijmer | Calciturbidites and calcidebrites: Sealevel variations or tectonic processes?[END_REF]. The gravelly gravity flows then decelerated and became less confined. The overlying tabular, fining-and thinning-upward series of sandstones and mudstones (HDTC to LDTC) mark the transition to lower energy depositional environments, resulting in passive filling and progressive abandonment of the channel system [START_REF] Galloway | Siliciclastic Slope and Base-of-Slope Depositional Systems: Component Facies, Stratigraphic Architecture, and Classification[END_REF][START_REF] Mchargue | Architecture of turbidite channel systems on the continental slope: Patterns and predictions[END_REF]. As in Fa2c-e, such sand-rich abandonment facies here suggest axis to offaxis settings [START_REF] Campion | Outcrop Expression of Confined Channel Complexes[END_REF]. Overall, these broadly lenticular and laterally extensive channel storey fills are dominated by sandy high-to low-density turbidites, scouring a mud-rich substrate during downslope transport and or at hydraulic jumps (i.e., abundant mud clasts) [START_REF] Fonnesu | Hybrid Event Beds Generated By Local Substrate Delamination On A Confined-Basin Floor[END_REF]). The vertically aggrading, semi-amalgamated style of the channel storey fills confirms a generally confined slope channel complex settings [START_REF] Sprague | Integrated slope channel depositional models: the key to successful prediction of reservoir presence and quality in Offshore West Africa[END_REF]), but less steep and confined to those of the previously described Fa2c-e.

Although most likely belonging to the same slope channel system, the uppermost occurrence Overall, we interpret the Waikaraka outcrop to represent the axis to off-axis stratigraphic infills of two distinct channel complexes, essentially capturing the early-to late-stage fills of a larger, yet confined slope channel system (sensu [START_REF] Sprague | Integrated slope channel depositional models: the key to successful prediction of reservoir presence and quality in Offshore West Africa[END_REF]). We further discuss the controls on such a system and the implications of its uppermost deposits in Section 7.

Weakly confined slope and depositional lobe systems

The Homewood section crops out one kilometer north of the Kaiwhata river mouth and extends over 110 meters along the coast (Figure 3). It features three distinct Middle Miocene, Lillburnian (Late Langhian to Serravallian, 15.1 -13.05 Ma, Appendix 2) gravity-driven systems described and interpreted below as three separate facies associations (Fa2c, Fa3p, Fa1g) (Figure 9).

Slope channel (Fa2c)

Observations

At Homewood, Fa2c is characterized by crude fining-and thinning-upward series, evolving from coarseto fine-grained facies. Owing to outcrop conditions, it is intermittently exposed for about 80 meters laterally and only represents a ten of meter-thick succession of sub-vertical beds. Its basal surface does not crop out and it is overlain by the erosive Fa3p (Figure 9).

Here, Fa2c is characterized by a series of tabular, continuous (1) medium-to thick-bedded (10 to 50 centimeters), disorganized (CF) to organized (gHDTC) clast-supported conglomerates with sandstone caps (SST), followed by ( 2) thin-to medium-bedded (3 to 15 centimeters) pebbly sandstones (sHDTC-a)

or bioclastic grits (sHDTC-b), either interbedded with mudstones (MDST) or structureless sandstones (SST-b) and mudstones (MDST), finally overlain by ( 3) medium-to thick-bedded bedded (10 to 50 centimeters) sandstones with mudstone caps (LDTC-b) (Figure 6; Figure 7; Figure 9; Figure 12g,h).

Overall, a greater internal organization is observed in Fa2c to the north-east of the outcrop.

Conglomerates are generally ungraded (CF) to the south-west of the outcrop, whereas they gradually show internal organization (gHDTC), displaying inverse-to normally-or only normally-graded patterns to the north-east (Figure 6). The conglomerates mostly consist of sub-angular to sub-rounded granule-to pebble-grade clasts (see Section 6). Cobbles and boulders are locally observed. Similarly, the bioclastic grits (sHDTC-b) become normally-graded, and include mud clasts and or bioclastic fractions aligned along horizons towards the north-east of the outcrop (Figure 7). In both cases, the basal surfaces of the conglomerates and bioclastic grits are slightly erosive and commonly display load structures. Finally, the sandstones (LDTC-b) to the south-west present rare, discontinuous, centimeter-thick, very coarse basal intervals (Ta), whereas to the north-east, these basal intervals are well-developed, fairly continuous and include frequent mud clasts and bioclastic fractions aligned along horizons, as well as load structures (Figure 7). The related sandstones also commonly show distinct grain-size breaks, indicating amalgamation of beds.

Interpretations

We interpret this basal succession to result from both flow processes and depositional environments (Fa2c) similar to those described at Waikaraka. While outcrop exposure hinders recognition of specific architectural elements, such as channels, and of particular depositional units (Fa2c-e, Fa2c-l), the stratigraphic infill outlines comparable crude fining-and thinning-upward conglomerate to sandstone series, resulting from gravelly to sandy high-to low-density turbidity currents [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF]. The main difference resides in the scale of the individual beds, being significantly smaller at Homewood, which could either point towards (1) smaller source region or slope-channel system, and or (2) contrasting locations along the slope or laterally within the channel.

Mixed shelf-derived mass-transport deposits (Fa3p)

Observations

Fa3p mostly comprises interbedded coarse-grained facies, here exposed across more than 120 meters laterally and about 15 meters thick (Figure 9).

Fa3p is characterized by a succession of thick-to very thick-bedded (<one to >two meters), disorganized, polymict, matrix-(DF) and clast-supported (CF) conglomerates, that laterally becomes entirely deformed and contorted (SL-a) to the north-east of the outcrop (Table 1; Figure 6; Figure 7; Figure 9). The conglomerates are recurrently capped by thin-to thick-bedded, either structureless or structured sandstones (SST) (Table 1; Figure 6; Figure 7; Figure 9; Figure 12), the latter of which can sometimes evolve to a few interbedded structured, very thin-to medium-bedded sandstones with mudstone caps, commonly bioturbated (LDTC-a) (Table 1; Figure 7; Figure 9; Figure 12b,e). elements supporting the interpretation of the Homewood 3D outcrop model (Figure 9). Fa2c corresponds to the confined slope channel system facies association, Fa3p to the shelf-derived mass-wasting system and Fa1g to the distal depositional lobe system. SL, CF, DF, gHDTC, SST, sHDTC, HDTC, LDTC correspond to the lithofacies summarized in Table 1. The basal surface is highly erosive (>8 meters) towards the north-east (Figure 9, red surface at the base of Fa3p; Figure 12g, i, j), and both local entrainment and deformation (i.e., apparent northward-verging contorted sandstones) of the substrate are observed (Figure 9; Figure 12g). In contrast, the upper surface is highly irregular, with overlying beds onlapping on a deci-to decametric scale (Figure 9; Figure 12a,b).

Laterally, the upper surface can appear rather flat and overlain by relatively tabular sandstones. The first overlying sandstone beds are generally internally chaotic; they sometimes incorporate material from Fa3p (e.g., pebbles and cobbles) and can form well-developed, decametric-scale soft-sedimentation deformation structures.

Five additional internal surfaces were also identified, which allows division of Fa3p into six units (Figure 9, blue surfaces within Fa3p). Commonly observed at the top of the structureless or structured beds (SST), these surfaces are sharp and characterized by thin-to medium-bedded silty mudstones (MDST)

that can be traced across the outcrop (Figure 9, blue surfaces; Figure 12d,h).

In the southern and central parts of the outcrop, Fa3p comprises fairly tabular beds. Their thicknesses tend to increase north-eastward, thus generally forming lens-like shapes opening towards the north-east (Figure 9). The beds' orientation changes from N055 to N035 and the dip measurements show an abrupt evolution from 90° (sub-vertical) to ~60° towards the west in only 15 meters. The dip of the first four units (separated by the internal surfaces described above) changes from 90° to 78°, whereas the remaining two directly onlap onto the preceding ones with a dip starting around 70° and evolving towards 60°. To the north-east, Fa3p is completely disorganized and shows SW-NE oriented recumbent folds (Figure 9, slump measurements; Figure 12j).

Three different scales of internal contortion are observed in Fa3p, evolving both vertically and laterally:

(1) at clast-scale;

(2) at unit-scale and ( 3) at the scale of several units. First, the entrained sandstones display both apparent NE-verging (Figure 9) and NE-SW-oriented recumbent folds (Figure 12f). Second, the fifth unit, previously observed to onlap on the underlying beds, appears to be severely folded, with a NE-SW main axis (Figure 9, unit 5; Figure 12b,e). Third, the upper Fa3p units become remobilized laterally, folding following an apparent NE-verging trend (Figure 12f). To the north-east of the outcrop, this remobilization involves the entire facies association (i.e., interbedded DF, CF and SST) (Table 1;

Figure 9; Figure 6; Figure 12f,i,j).

The matrix of the interbedded polymict conglomerates generally represents 40 to 70% of the DF deposits with two occurrences comprising up to 80% of matrix (Figure 6; Figure 12b, e; Figure 13), and <5 to 15%

in CF. DF can display slight upward increase in matrix content. Alternatively, DF commonly shows vertical and or lateral variations in both clast concentration and size at its base, top and or edges that appear akin to the clast-supported lithofacies (CF) (Figure 9; Figure 6; Figure 12c,d,e,g,h). These concentrated intervals are characterized by clasts of smaller grades (i.e., granule-to pebble-grade) than those of the general matrix-supported intervals (i.e., pebble-to cobble-grade) (Figure 6). Overall, the average clast size is of pebble-to cobble-grade in DF, whereas granule-to pebble-grade dominates CF. In DF, larger clasts are frequent and can be outsized (deci-to decametric); conversely, they are rare and of cobblegrade in CF. In both DF and CF, clast edges typically vary between sub-angular to sub-rounded shapes.

The highest proportions of sub-angular clasts are found in the largest clasts (e.g., boulders). Sub-rounded to rounded clasts are mostly present in the concentrated granule-to pebble-grade intervals of DF or in some rare occurrences of CF.

Interpretations

We interpret Fa3p to represent deposition (i.e., mass-transport deposits [MTDs]) from successive masswasting events that triggered recurrent debris flows (DF and CF) [START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF][START_REF] Mulder | Classification of offshore mass movements[END_REF]. The clast-supported debris flows (CF) are inferred to result from cohesionless flows [START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF]). Even if matrix strength dominates in DF, thereby suggesting cohesive flows [START_REF] Nardin | A review of mass movement processes, sediment and acoustic characteristics, and contrasts in slope and base-of-slope systems versus canyon-fan-basin floor systems[END_REF][START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF]), [START_REF] Nemec | Alluvial and Coastal Conglomerates: Their Significant Features and Some Comments on Gravelly Mass-Flow Deposits[END_REF] demonstrated that the predominance of matrix in conglomerates was not always a criterion to discriminate cohesive and cohesionless debris flows. Although the ungraded, disorganized and matrix-rich occurrences of DF result from cohesive flows [START_REF] Johnson | Debris flow[END_REF][START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF]), the 2-to-3 phase occurrences (sheared DF) show internal organization that indicates fully sheared flows with additional support mechanisms, such as grain collisions and dispersive pressure, characteristic of cohesionless debris flows [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF][START_REF] Nemec | Alluvial and Coastal Conglomerates: Their Significant Features and Some Comments on Gravelly Mass-Flow Deposits[END_REF][START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF]).

Multiphase debris flows require steep slopes [START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF]). The lens-like shapes observed in some of Calhoun and Clague 2018). The high-amplitude variations recorded in the dip of beds (~40°) indicates that they were syn-kinematic with the rise of a structure to the east, i.e., growth strata. Changes in slope gradient chiefly impact flow behavior (e.g., velocity) and may promote flow transformations (e.g., dilution, shearing) [START_REF] Fisher | Flow transformations in sediment gravity flows[END_REF], which in turn control the nature and geometry of the resultant deposits. Hence, slope angle changes could partly explain the variety of debris flow deposits recorded in Fa3p. Also, the considerable amounts of granule-and pebble-grade clasts [START_REF] Sohn | Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)[END_REF] as well as the recurrent presence of mudstone layers and fine sandstones (SST), respectively under-and overlying the conglomerates, all point toward fast-moving debris flows that hydroplane (sensu [START_REF] Mohrig | Hydroplaning of subaqueous debris flows[END_REF]. The multiphase debris flows described here would thus result from efficient dilution of cohesive, hydroplaning debris flows [START_REF] Mohrig | Hydroplaning of subaqueous debris flows[END_REF]; dilution which can arise only a few kilometers from the source areas [START_REF] Sohn | Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)[END_REF] and which can lead to the generation of slower-moving suspended sediment clouds eventually depositing above them (SST) [START_REF] Mohrig | Hydroplaning of subaqueous debris flows[END_REF][START_REF] Sohn | Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)[END_REF][START_REF] Mohrig | Constraining the efficiency of turbidity current generation from submarine debris flows and slides using laboratory experiments[END_REF][START_REF] Talling | Beds comprising debrite sandwiched within co-genetic turbidite: origin and widespread occurrence in distal depositional environments[END_REF]). The first debris flow, however strongly erosional, suggests both an abrupt change in the depositional settings to that of the underlying Fa2c deposits and an initially different mechanism (i.e., substrate erosion) responsible for flow mobility [START_REF] Sobiesiak | Styles of basal interaction beneath mass transport deposits[END_REF]).

The internal surfaces allow to distinguish at least six mass-wasting events. The different scales of internal contortion and deformation observed in the Fa3p deposits however complicates their depositional history, thereby questioning the hypothesis of simple deposition of one mass flow on top of another. Basal deformation of the substrate linked to the passage of an overriding flow is common, however the flow mobility mechanisms proposed here (i.e., hydroplaning) diverges from such a scenario, promoting little to no interaction between the moving flow and underlying deposits for five of the units [START_REF] Sobiesiak | Styles of basal interaction beneath mass transport deposits[END_REF]. Notwithstanding the possibility for the contorted strata to shear and deform in the direction of the flow and thus capture the paleoslope direction at the clast-scale [START_REF] Fonnesu | Hybrid Event Beds Generated By Local Substrate Delamination On A Confined-Basin Floor[END_REF] to greatly affect slope stability and encourage its failure [START_REF] Hein | Geotechnical aspects of fine-grained mass flow deposits: California Continental Borderland[END_REF]. Finally, the micropaleontological studies imply an upper-to mid-bathyal depositional environment (Appendix 2).

Distal depositional lobe system (Fa1g)

Observations

Fa1g is characterized by laterally continuous, on average medium-bedded (~14 centimeters) and finegrained sandstones that show decreasing bed dips upward (56° to 32°). This association is exposed along ~one kilometer of coastline and is over 200 meters in thickness (Appendix 4). Only the lowermost part of this system is described in context of the outcrop model presented in this study (Figure 9; Fa1g).

Fa1g mostly comprises interbedded tabular, medium-to thick-bedded, frequently amalgamated sandstones (LDTC-b) and very thin-to medium-bedded (LDTC-a), often dewatered, argillaceous sandstones (Table 1; Figure 7). Most beds include shell fragments and plant debris in the structured intervals, and are capped by silty mudstones that regularly include bioturbations (Figure 7) such as Phycosiphon sp., Zoophycos sp., Skolithos sp. and Scolicia sp. Episodes of thin-bedded bioclastic grits (sHDTC-b) are recurrent (Figure 7). Very-thick sandstone beds punctually occur; they tend to have sole marks, several grain-size breaks, and sometimes show decametric soft-sedimentation deformation structures. A few lenticular, medium-to very thick-bedded sandstones (HDTC) are also observed. Their incision rarely exceeds 50 centimeters and can comprise coarse bioclastic material (Figure 7).

Paleocurrent measurements from sole marks and traction structures generally indicate a north-eastward direction at the base of this system (Figure 9). Finally, disorganized, contorted strata (SL-a) and coherent, remobilized strata displaying sharp internal truncations in the same lithofacies (SL-b) recurrently interrupt the strata (Table 1; Figure 6).

Interpretations

Fa1g is interpreted to record the emplacement and sustained development of a distal depositional lobe system [START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Prélat | Evolution, architecture and hierarchy of distributary deep-water deposits: a highresolution outcrop investigation from the Permian Karoo Basin, South Africa[END_REF][START_REF] Mcarthur | Deformation-sedimentation feedback and the development of anomalously thick aggradational turbidite lobes: subsurface and outcrop examples from the Hikurangi Margin, New Zealand[END_REF]) installed above and subsequently pinned at its base within the rugose topography left by the underlying MTDs (e.g., [START_REF] Bull | A review of kinematic indicators from mass-transport complexes using 3D seismic data[END_REF][START_REF] Armitage | The Influence of Mass-Transport-Deposit Surface Topography on the Evolution of Turbidite Architecture: The Sierra Contreras, Tres Pasos Formation (Cretaceous), Southern Chile[END_REF]) (Figure 9; Figure 12a,b). These laterally extensive, tabular, sandstone-rich deposits are interpreted as the deposits of dominantly low-density turbidity currents (LDTC) [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF], commonly deposited in off-axis to fringe positions [START_REF] Prélat | Evolution, architecture and hierarchy of distributary deep-water deposits: a highresolution outcrop investigation from the Permian Karoo Basin, South Africa[END_REF]). The punctual bioclastic grits as well as the locally erosive, amalgamated and very thick occurrences, are however attributed to higherdensity turbidity currents [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF] geometries as well as the recurrent yet localized remobilization of strata both suggest an unstable depositional environment, likely due to a continued rise of the eastern structure. The paleocurrent directions to the NE indicate that the flow at the start of this depositional system was parallel to the rising NE-SW oriented structure to the east and thus both point towards a different sourcing system to the underlying MTDs (see Section 5.3.2) and an axial routing of the turbidity currents [START_REF] Burgreen | Evolution of a deep-water lobe system in the Neogene trenchslope setting of the East Coast Basin, New Zealand: Lobe stratigraphy and architecture in a weakly confined basin configuration[END_REF]. The abundance of land-derived material suggest that these turbidity currents likely initiated from a shallow marine environment connected to a hinterland (Kuenen 1964), while the micropaleontology analyses indicate that deposition of the turbidites occurred at mid bathyal depths or deeper (> 800 meters) (Appendix 2).

SOURCE REGIONS

Despite lithofacies similarities, the sediment gravity flows observed at Waikaraka and Homewood are lithologically different (Figure 13) and thus indicate different sediment sources. Here, we use the nature of the reworked material in the conglomerates (DF, CF, gHDTC, gsHDTC), pebbly sandstones (sHDTCa), bioclastic grits (sHDTC-b) and coarser intervals of the sandstones (HDTC) as a tool for better understanding and characterizing their provenance and source areas as well as deciphering local paleotransport directions (e.g., [START_REF] Nemec | Alluvial and Coastal Conglomerates: Their Significant Features and Some Comments on Gravelly Mass-Flow Deposits[END_REF].

Extrabasinal sources

Clast observations

Across both Waikaraka and Homewood, the conglomeratic units (DF, CF, gHDTC, gsHDTC, sHDTC, HDTC) essentially rework extraformational clasts from pre-and syn-subduction strata (>95%) (Figure 13). Pre-subduction material dominates (> 80%) and comprises lithoclasts from the Early Cretaceous up to the Paleocene at Waikaraka and from the Late Cretaceous up to the Eocene at Homewood. The synsubduction material is divided into Miocene lithoclasts and bioclasts. belonged to and the bioclasts were subdivided into two main types, i.e., the preserved skeletons and the shell fragments. DF, CF, gHDTC, gsHDTC and HDTC correspond to the lithofacies summarized in Table 1.

Intraformational clasts are virtually absent (<1%) in CF, but are more frequent in the conglomerates deposits resulting from matrix strength (DF; e.g., poorly lithified turbidites) and fluid turbulence (gHDTC, gsHDTC, sHDTC, HDTC; e.g., mud clasts).

Clast interpretations

The dominance of extraformational clasts implies that the flows responsible for these conglomeratic units initiated outside of their final depositional environment and incorporated material belonging to structural units and or paleogeographic domains different to that of the intrabasinal sediments (i.e., extrabasinal) (e.g., [START_REF] Ogata | Substrate deformation and incorporation in sedimentary mélanges (olistostromes): Examples from the northern Apennines (Italy) and northwestern Dinarides (Slovenia)[END_REF]. The abundance of pre-subduction material indicates that during the Middle Miocene, the exposed extrabasinal paleogeography was dominated by Cretaceous to Eocene strata. In compressional settings, uplift of thrust-related structures is known to develop bathymetric highs and or steep slopes, which can in turn, expose rocks from the older substratum (i.e., pre-subduction), ready to be reworked and incorporated into the subsequent flows and MTDs (e.g., [START_REF] Ogata | Substrate deformation and incorporation in sedimentary mélanges (olistostromes): Examples from the northern Apennines (Italy) and northwestern Dinarides (Slovenia)[END_REF]).

Mixed siliciclastic-carbonate shelves

Bioclast observations

A substantial amount (~10 to 40%) of syn-subduction bioclasts is present in all the deposits, either as shell fragments or as well-to partly-preserved skeletons (Figure 13). Molluscan species (e.g., bivalves and gastropods) dominates; yet, corals (solitary and colonial) and red algae are also locally present (Appendix 3). At Homewood, the preserved forms of macrofossils reach between 15 and 25% of the bioclasts contained in the debris flow deposits (DF and CF) whereas they are virtually absent in the turbidites (gHDTC and HDTC), which are dominated by shell fragments. At Waikaraka however, the preserved forms represent a considerably larger proportion of the bioclasts, mostly oscillating between 25 and 40%, even at the base of the turbidites (gHDTC and HDTC). Although the content in both the coarse (macrofossils) and fine (shell fragments) skeletal fractions gradually increases toward the top of the Waikaraka deposits, this upward evolution is particularly remarkable in the late-stage fill deposits (Fa2c-l) (Figure 13,cf. c2,c3,d,e).

Overall, the taphonomic analyses shows that destructive processes dominate the taphonomic record of the deposits, constructive taphonomic processes such as encrustation being virtually absent (Figure 14).

At Homewood, the deposits are characterized by bioclasts being: (1) (2) moderately abraded and, (3) poorly bioeroded. At Waikaraka, the finer bioclastic fractions compare markedly in both debris flows (DF, CF) and high-density turbidite flows (gHDTC, gsHDTC). By contrast, the coarser skeletal material in the former exhibit higher degrees of abrasion and bioerosion than in the latter (Figure 14).

Bioclast interpretations

The nature and amount of reworked molluscan species indicate that the sediment gravity flows originated from shallow marine middle-to inner-shelf neritic environments before being transported to deep-marine outer to mid bathyal depths (Appendix 2; Appendix 3).

The contemporaneously developing mixed siliciclastic-carbonate environments (i.e., compositional systems (sensu Chiarella et al. ( 2017)) previously identified and described in the Coastal Ranges present markedly similar faunal assemblages [START_REF] Crundwell | Neogene stratigraphy and geological history of the Wainuioru Valley[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF] and are thus great candidates for providing both the preserved skeletons and shell fragments. The depositional system envisaged for those sources is one of a regional, continentattached shelf domain, recurrently supplied with terrigenous sediments from the exposed Cretaceous basement located to the west [START_REF] Crundwell | Neogene stratigraphy and geological history of the Wainuioru Valley[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF][START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF].

The substantial amount of gravels transported beyond the shelf and captured within the deposits (see Sections 5 and 6.3) requires narrow shelf settings to easily connect to the slope beyond [START_REF] Nemec | Alluvial and Coastal Conglomerates: Their Significant Features and Some Comments on Gravelly Mass-Flow Deposits[END_REF], which typify the shelfal systems along active margins [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF]. No lateral continuity has yet been proven between the mixed siliciclastic-carbonate environments and therefore, isolated, continent-detached shelfal systems likely also developed locally (e.g., [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF],

Fingerpost shelf) upon and around actively growing folds and faults [START_REF] Caron | Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand[END_REF]) (see Section 6.3 and 7).

In fact, at Waikaraka, the fairly constant proportion of shelfal macrofossils found throughout the 90 meterthick succession points to paleophysiographies allowing for molluscan communities to thrive above storm-wave base [START_REF] Pomar | Ecological control of sedimentary accommodation: evolution from a carbonate ramp to rimmed shelf, Upper Miocene, Balearic Islands[END_REF]. At Homewood however, the macrofossils are mostly found in the conglomerates (DF, CF) of the mass-wasting system (Fa3p) and their quantity tends to be generally smaller to that of Waikaraka. This could indifferently indicate a smaller-sized source area, slightly different paleoenvironmental conditions at the source as well as different transport processes and distances. The paleotransport directions recorded in the mass-wasting system (Fa3p) of Homewood also inform that the Conversely, the profuse shell fragments found in the overlying, well-developed, north-eastward prograding turbidite system (Fa1g) indicate a change of source region, likely belonging to the main westward continent-attached shelf domain.

The regular detrital sand and pebble supply (see Sections 5 and 6.3) likely restricted the development of carbonate factories dominated by suspension-feeding organisms [START_REF] Caron | Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand[END_REF]), thereby promoting molluscan communities (Bimol assemblage of [START_REF] Hayton | A skeletal assemblage classification system for non-tropical carbonate deposits based on New Zealand Cenozoic limestones[END_REF]) often associated with relatively turbid waters due to fine material in suspension. The occurrence in the deposits of occasional coralline red algal branches and small-sized-rhodoliths indicate sources within the photic zone [START_REF] Pomar | Ecological control of sedimentary accommodation: evolution from a carbonate ramp to rimmed shelf, Upper Miocene, Balearic Islands[END_REF][START_REF] Nebelsick | Facies dynamics in Eocene to Oligocene circumalpine carbonates[END_REF].

Differences in the degrees of taphonomic alteration observed in skeletal remains relate to their residence time in the taphonomic active zone (TAZ; [START_REF] Davies | Relative rates of shell dissolution and net sediment accumulation -a commentary: can shell beds form by the gradual accumulation of biogenic debris on the sea floor?[END_REF])). Typically, taphonomic alteration consistently increases with increasing residence time in the TAZ where skeletons are affected by destructive processes, such as disarticulation, fragmentation, abrasion and bioerosion. For example, low net sedimentation rates and repeated exhumation of buried skeletal remains by waves and currents, and by seafloor burrowers favor mechanical destruction and bioinfestation. By contrast, rapid and definite burial prevents such alterations (e.g., Best and Kidwell 2000;[START_REF] Best | Carbonate Preservation in Shallow Marine Environments: Unexpected Role of Tropical Siliciclastics[END_REF]). Fragmentation of skeletal remains over three centimeters in size is moderate to high, both at Waikaraka and Homewood in debris flows and turbidite flows (Figure 14). Although it cannot be ruled out that skeletons were partly fragmented in their source area through hydraulic and biological processes [START_REF] Zuschin | Patterns and processes of shell fragmentation in modern and ancient marine environments[END_REF], it should be expected that fragmentation also occurred, as a result of mechanical crushing, once they were integrated in their host clast-supported gravity-driven flows. Abrasion of the coarser skeletal fraction, translating in the loss of ornamentation and rounding of bioclast edges, is: (1) higher in debris flows than in turbidite flows, and (2) overall higher than fragmentation in debris flows compared to turbidite flows. Abrasion is caused by physical erosion, through friction and at a lesser degree through waterborne collision, and reworking leading to mobilization and redeposition of bioclasts. Moderate to high degrees of abrasion, along with the abundance of small-sized skeletal debris, are indicative of frequently destabilized substrates by wave action, storms and, potentially here, gravity-driven flows (e.g., [START_REF] Kowalewski | Time-Averaging, Overcompleteness, and the Geological Record[END_REF].

Further, such unstable substrates may have inhibited colonization of dead shells by encrusters, and their infestation by borers, thereby explaining the low degrees of taphonomic alteration for these processes (Figure 14). However, possible causes for the observed differences in biogenic alteration (slightly higher in Waikaraka debris flow deposits for example) are multifarious, including high-sedimentation rates leading to rapid burial, unsuitable shell substrates and/or ecological conditions for infester communities [START_REF] Caron | A new analytical procedure to graphically characterize the taphonomic properties of skeletal carbonates. An example from Miocene limestones of new zealand[END_REF].

Results of the taphonomic evaluation suggest that the alteration state of skeletal remains in the studied deposits not only reflects depositional and ecological conditions at the site of carbonate production on the shelf, but has also potential to record conditions of transport during their remobilization in gravitydriven systems. In particular, the taphonomy of skeletal contents, as a complementary tool to other analytical approaches, may provide clues on the laminar (i.e., debris flows) versus turbulent (i.e., turbidites) character of flow, and whether deposition by traction sedimentation prevailed over suspension sedimentation [START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF]).

Distinct substratum and continental connection

Lithoclast observations

At Homewood, the extra-and intraformational lithoclasts tend to oscillate between sub-angular to subrounded shapes and are in average of granule-to pebble-grades in the confined channel fills (Fa2c) and granule-to cobble-grades in the mass-wasting system (Fa3p). Conversely, at Waikaraka, sub-rounded clasts dominate and sub-angular shapes only preferentially occur in the early-stages confined channel fills (Fa2c-e). At Waikaraka, the clast grades also largely depend on the style of channel fills, and are preferentially of pebble-to outsized-grades in the early-stages fills (Fa2c-e) and of pebble-grades in the late-stage fills (Fa2c-l) (see Section 5).

Pre-subduction extraformational clasts largely dominate representing 95 to 99% of the overall lithoclast content at Homewood and 84% to 97% at Waikaraka (Figure 13). They mostly rework (>80%) Upper

Cretaceous strata (e.g., mainly siliceous and calcareous mudstones, rare lavas) and frequently include (~4 to 10%) Paleocene clasts (e.g., limestones). Conversely, Lower Cretaceous clasts (e.g., Torlesse greywackes) are only observed, sporadically (~2%), at Waikaraka, whereas Eocene clasts (e.g., smectitic mudstones) are virtually absent and only rarely found (~1%) at Homewood (Figure 13).

At Waikaraka, the early-stage fills of the first channel complex (Fa2c-e) deviate from this model, the confined slope channel system (Fa2c) (Figure 13). They are preferentially restricted to particular conglomerate intervals (CF, gHDTC) of the confined channel fills, generally located at the top of the earlystage fills (Fa2c-e).

The syn-subduction extraformational lithoclasts most commonly include pebble-to boulder-grade clasts of lithified shell beds. They are frequent in the confined slope channel system of Waikaraka. There The remaining syn-subduction extraformational lithoclasts comprise pebble-grade wood fragments and disseminated plant debris. A few cobble-to boulder-grade clasts of fossil tubular concretions [START_REF] Malie | Spatial distribution and tectonic framework of fossil tubular concretions as onshore analogues of cold seep plumbing systems, North Island of New Zealand[END_REF] were also observed in the early-stage fills (Fa2c-e) at Waikaraka.

Finally, the syn-subduction intraformational lithoclasts are characterized by outsized, contorted sandstones and pebble-to boulder-grade mudstone clasts. The outsized, contorted sandstones are generally restricted to DF, particularly at Homewood; whereas the mudstone clasts, although present in some of the conglomerates, are dominantly found in the coarse-grained basal intervals of the sandstones at both Waikaraka and Homewood.

Lithoclast interpretations

As previously observed elsewhere in the Coastal Ranges [START_REF] Neef | Geology of the Akitio area (1:50 000 metric sheet U25BD, east), northeastern Wairarapa, New Zealand[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF], the nature of the extraformational lithoclasts informs that the mixed siliciclastic-carbonate shelfal domain sourcing the Waikaraka deposits developed above a pre-(e.g., Cretaceous to Paleogene series) and syn-subduction (e.g., Miocene sediments) substratum, whereas the paucity of extraformational syn-subduction clasts (e.g., a couple of shell bed clasts) at Homewood suggests a presubduction-dominated substratum. At Waikaraka, the variety encountered in both the proportion and nature of pre-subduction material informs that the basal deposits of the confined slope channel system (Fa2c) remobilized the entire presubduction series down to the Lower Cretaceous, whereas the remainder mostly captured remobilized Upper Cretaceous strata (Figure 13). The absence of Lower Cretaceous greywackes and predominance of Upper Cretaceous strata at Homewood both suggest a slightly different substratum and or exhumed paleobathymetric high sourcing the deposits. The implications for both these localities are discussed in Section 7.

At Waikaraka, the syn-subduction material, mostly comprising shell bed clasts, likely results from destabilization of previously deposited and lithified strata (i.e., substratum) rather than contemporaneous sediments. Their diversity captures different mixed siliciclastic-carbonate shelfal environments, which either (1) belonged to the same shelfal system, thus suggesting different phases of shelf development or local variations in depositional settings [START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF], and or (2) resulted from distinct shelfal systems that formed in the area since the onset of subduction [START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Caron | Episodes of seabed rise and rapid drowning controlling the development of regressive and transgressive rhodolithic limestones in a tectonically-active subduction setting (Early Miocene, Wairarapa region, New Zealand)[END_REF]. Conversely, at Homewood, the occasional sandy shell beds could be contemporaneous with the development of the shelfal environment. Early lithification of the deposits at or near the seafloor may have been triggered by increased saturation of seawaters with respect to CaCO3, following partial dissolution of aragonitic turritellid shells, though such process has been documented to predominantly result from burial diagenesis (i.e., mesodiagenesis) [START_REF] Nicolaides | Cementation in Oligo-Miocene non-tropical shelf limestones, Otway Basin, Australia[END_REF][START_REF] Haywick | Diagenesis of polymineralic temperate limestones in a cyclothemic sedimentary succession, eastern North Island, New Zealand[END_REF][START_REF] Caron | Diversity of Neomorphic Fabrics in New Zealand Plio-Pleistocene Cool-Water Limestones: Insights into Aragonite Alteration Pathways and Controls[END_REF].

The abundant pebble-grade to outsized sub-angular clasts found in the confined slope channel (Fa2c)

and mass-wasting system (Fa3p) of Homewood, and more sporadically in the early-stage confined channel fills (Fa2c-e) of Waikaraka, both indicate that despite clast interactions, not only the sediment sources were nearby but also that the material was "freshly" eroded to allow preservation of such features [START_REF] Postma | Large floating clasts in turbidites: a mechanism for their emplacement[END_REF].

Notwithstanding partial remobilization of the shelf and slope substratum through submarine destabilization (e.g., mass-wasting failure) and or erosional processes (e.g., channel cutting through the slope substratum) to provide for most of the lithoclast content (e.g., [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF][START_REF] Janocko | The diversity of deep-water sinuous channel belts and slope valley-fill complexes[END_REF][START_REF] Paumard | Controls On Deep-Water Sand Delivery Beyond the Shelf Edge: Accommodation, Sediment Supply, and Deltaic Process Regime[END_REF], dismantlement and erosion of exhumed paleobathymetric highs probably contributed as well (e.g., [START_REF] Ogata | Substrate deformation and incorporation in sedimentary mélanges (olistostromes): Examples from the northern Apennines (Italy) and northwestern Dinarides (Slovenia)[END_REF]. In fact, the presence of wood fragments and plant debris in both settings informs that the source areas were connected to a terrestrial ecosystem [START_REF] Phh | Deep-Sea Sands and Ancient Turbidites[END_REF] resided for at least some time in a littoral zone, before being transferred to bathyal depths [START_REF] Celma | Sedimentology, architecture, and sequence stratigraphy of coarse-grained, submarine canyon fills from the Pleistocene (Gelasian-Calabrian) of the Peri-Adriatic basin, central Italy[END_REF]. Where grain collision is inferred as a dominant grain-support mechanism (e.g., in most of the Fa2c and Fa3p deposits), it can also be expected to have favored the quick abrasion and rounding of the harder, coarse-grained clasts.

The large volume of wood fragments and plant debris recorded throughout the confined slope channel deposits of Waikaraka (Fa2c) and the well-developed turbidite system of Homewood (Fa1g) both support source connections to mature hinterlands (e.g., [START_REF] Stanley | Turbidity current transport of organic-rich sediments: Alpine and Mediterranean examples[END_REF]McArthur et al. 2016b). The discrete occurrences observed in the mass-wasting system of Homewood (Fa3p) rather points toward a small and or isolated source system, such as an island developed above tectonically-controlled topography (McArthur et al. 2016a), hence reinforcing the hypothesis of a source system detached from the main shelf domain.

Finally, the nature of intraformational clasts, such as mud clasts, informs that these gravity flows were erosive and ploughed through mud-prone substrates as they moved downslope or at hydraulic jumps [START_REF] Posamentier | The Character and Genesis of Submarine Mass-Transport Deposits: Insights from Outcrop and 3D Seismic Data[END_REF]. At Homewood, the contorted sandstones also indicate of the varying nature of the ploughed substrate, locally supported by the underlying sandier deposits (Fa2c).

DISCUSSION

7.1. Gravity-driven systems from forelimb, continent-attached shelfal source

The depositional system proposed for Waikaraka is one of a confined slope channel system (CSCS) (sensu [START_REF] Campion | Outcrop Expression of Confined Channel Complexes[END_REF] distributing land-derived, shallow-and deep-marine bedrock-derived sediments to the trench-slope basin.

As interpreted (see Sections 5 and 6), this system was likely sourced from the regional, narrow and continent-attached mixed siliciclastic-carbonate shelfal domain, which was contemporaneously developing to the west during the Middle Miocene, atop seaward-verging thrust-cored anticlines (Figure 15A; Figure 16) [START_REF] Crundwell | Neogene stratigraphy and geological history of the Wainuioru Valley[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF][START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF].

Precise geometry of the slope upon which the CSCS developed is here a matter of speculation; yet, the forelimb settings rather suggest a steep, probably irregular, tectonically-controlled gradient close to the shelf edge and across the slope (Figure 15A; Figure 16) (e.g., [START_REF] Naranjo-Vesga | Regional controls in the distribution and morphometry of deepwater gravitational deposits along a convergent tectonic margin[END_REF]. The large volume of terrigenous material as well as the nature of the reworked clasts (e.g., well-preserved bioclasts, shell fragments, pre-subduction strata) recorded throughout the CSCS deposits (Fa2c) both indicate persistent connection with a shelfal domain, recurrently supplied by the mature, vegetated hinterland to the west, exhumed since the onset of the Hikurangi subduction and mostly exposing Cretaceous strata (Figure 16) [START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF].

Along active margins, CSCS commonly represents long-lived transport routes for sediments across the shelf and slope that are typically insusceptible to sea-level changes and directly connect the hinterland (Type I, shelf-incising and river-associated system of [START_REF] Harris | Global distribution of large submarine canyons: Geomorphic differences between active and passive continental margins[END_REF]) and or shoreface depositional systems (Type II, shelf-incising system of [START_REF] Harris | Global distribution of large submarine canyons: Geomorphic differences between active and passive continental margins[END_REF]) to the deep sea [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF]). Here however, although regional tectonics (i.e., margin uplift) largely governed the initial emplacement of this mixed siliciclastic-carbonate shelfal domain installed atop thrust-cored anticlines [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF], eustatic processes appear to then chiefly control their development and stratigraphic architecture [START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF]. Notwithstanding the reworking of Upper Cretaceous conglomerates characteristically rich in already-reworked Lower Cretaceous Torlesse greywackes [START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF] as a potential source for providing gravels readily available to be transferred across the narrow shelf, the punctual input of well-rounded pebbles of Torlesse greywackes observed at the top of the early-stages fills of the CSCS (see Section 6) could also be attributed to an intermittent connection of the shelf with river(s). The successive T-R sequences that characterize these shelfal environments [START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF]) could explain such periodic communication with the exhumed Cretaceous hinterland and would in turn suggest some eustatic control here, eventually captured in the CSCS infill.

The broad fining-and thinning-upwards trends observed in the CSCS (Fa2c) are common in many other slope channel systems, indicating channel bypass and backfilling processes (e.g., [START_REF] Mutti | Turbidite Systems and Their Relations to Depositional Sequences[END_REF][START_REF] Deptuck | Architecture and evolution of upper fan channel-belts on the Niger Delta slope and in the Arabian Sea[END_REF][START_REF] Beaubouef | Deep-water leveedchannel complexes of the Cerro Toro Formation, Upper Cretaceous, southern Chile[END_REF][START_REF] Sylvester | A model of submarine channel-levee evolution based on channel trajectories: Implications for stratigraphic architecture[END_REF][START_REF] Kneller | Architecture, process, and environmental diversity in a late cretaceous slope channel system[END_REF]. The repeating series of architecture and facies associations inform that this CSCS system likely behaved in a cyclic manner through time that may well have been in phase with the sea-level changes, yet likely also resulted from external forcing factors, such as pulses of thrust fault activity (e.g., uplift and or related seismicity) at the edge of the shelf, known to periodically renew erosion and active sediment transport into CSCS along active margins (e.g., [START_REF] Mountjoy | Morphostructure and evolution of submarine canyons across an active margin: Cook Strait Accepted Manuscript version[END_REF][START_REF] Mountjoy | Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins[END_REF][START_REF] Watson | Tectonic and geomorphic controls on the distribution of submarine landslides across active and passive margins, eastern New Zealand[END_REF].

Interestingly, the reworked material contradicts the traditional unroofing model, incorporating clasts from the entire Lower Cretaceous to Paleogene pre-subduction strata only within its lowermost record and or slope erosion (e.g., [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF]). These processes exposed the underlying submarine bedrock of the thrust-cored anticline (i.e., forelimb setting) upon which the shelfal domain developed, making it ready to be included into the subsequent gravity flows (Figure 15A; Figure 16) (e.g., [START_REF] Ogata | Substrate deformation and incorporation in sedimentary mélanges (olistostromes): Examples from the northern Apennines (Italy) and northwestern Dinarides (Slovenia)[END_REF].

For the latter contrasting clast content, we here infer the autogenic evolution of this shelf-incising CSCS (Type I, shelf-incising and river-associated system of Harris and Whiteway ( 2011)) during late low-stand conditions, whereby retrogressive erosion at the head of the system (sensu [START_REF] Daly | Origin of submarine canyons[END_REF] would have favored the failure, storage and reworking of the marginal siliciclastic-carbonate sediments, contemporaneously (e.g., living or freshly deceased macrofauna, terrigenous debris) and previously deposited (e.g., shell bed lithoclasts), along with their underlying substratum, here dominated by Upper Cretaceous strata (Figure 15B; Figure 16). The upward increase of bioclastic material recorded in the channel fill may also partially illustrate such progressive upslope variation in source region, whereas the dominance of skeletal grains (over non-skeletal, e.g., ooids, pellets) typically occur during such sea-level low-stands [START_REF] Reijmer | Calciturbidites and calcidebrites: Sealevel variations or tectonic processes?[END_REF].

Here, regional tectonics appear to have chiefly governed both the birth (emplacement) and death (drowning) of ( 1) the continent-attached mixed siliciclastic-carbonate shelfal domain installed atop thrustcored anticlines [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF][START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF] and of ( 2) its related shelf-derived, deep-marine systems. Whilst the shelfal domain development then became largely eustatically-controlled [START_REF] Bailleul | Modalités de la sédimentation de plate-forme sur la pente d'un prisme d'accrétion: l'exemple du Miocène Moyen du prisme Hikurangi (Nouvelle-Zélande)[END_REF], the combination of steep slope gradient, high sediment supply and narrow shelf width resulted in the development of a CSCS (Fa2c) that efficiently transferred the shelf-derived sediments to the deepmarine environments (e.g., [START_REF] Naranjo-Vesga | Regional controls in the distribution and morphometry of deepwater gravitational deposits along a convergent tectonic margin[END_REF]. Although punctually capturing the sea-level changes, the overall evolution and geometry infill of the CSCS seemed essentially controlled by local tectonic activity at the mixed siliciclastic-carbonate shelf edge, which, in turn, determined its stratigraphic infill (sediment distribution and architecture) (Figure 15; Figure 16).

The abrupt changes in sedimentation styles (i.e., sand-dominated) and paleodepth of deposition (i.e., lower bathyal) recorded in the uppermost CSCS deposits (see Section 5; Appendix 2) could be attributed to the major change in tectonic regime (i.e., generalized subsidence) that was recorded along the Hikurangi margin at the time, which in turn resulted in rapid bathymetric deepening of the area (i.e., highstand conditions) [START_REF] Chanier | Extensional deformation across an active margin, relations with subsidence, uplift, and rotations: The Hikurangi subduction[END_REF]; D5 discontinuity and U5 unit of [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF]) (Figure 10a, e). Direct coarse-grained sediment supply stopped; yet, some high-stand activity was maintained along the CSCS (e.g., [START_REF] Mountjoy | Morphostructure and evolution of submarine canyons across an active margin: Cook Strait Accepted Manuscript version[END_REF].

Gravity-driven systems from backlimb, continent-detached shelfal source

The source and depositional system envisaged at Homewood contrast with the coeval continent-attached shelfal environment and slope channel delivery system of Waikaraka. As previously described (see controlled by an underlying seaward-verging thrust (i.e., backlimb setting) [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF], their figure 12).

At Homewood, the shelf was likely cut by a network of small slope channels connecting the island through the shelf to the Whareama Basin (Fa2c) (Figure 16). The transition from slope channel (Fa2c) to shelfderived mass-wasting (Fa3p) systems is attributed to a period of tectonic activity (e.g., uplift) at the basinbounding structure, resulting in growth strata deposition on the eastward-margin of the basin (see Section 5.

3) (e.g., [START_REF] Moore | Development of sedimentary basins on the lower trench slope[END_REF][START_REF] Stevens | Deformational and sedimentary processes in trench slope basins of the western Sunda Arc, Indonesia[END_REF] and typically lasting 1 to 2 Ma in these settings [START_REF] Nicol | Growth of contractional structures during the last 10 m.y. at the southern end of the emergent Hikurangi forearc basin, New Zealand[END_REF][START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF].

Structure growth both (1) promoted the repeated destabilization of the isolated shelf and generation of the Fa3p mass-wasting flows as well as ( 2) controlled the axial routing and syn-kinematic development of the overlying Fa1g turbidite lobe system sourced from the mature hinterland to the west (Figure 16).

The associated MTDs (Fa3p), only ~15 meters thick, recorded a difference of ~40° in bed dips (i.e., growth strata), thereby indicating complex interplay between the growing structure and sediment deposition. The slope gradient acted as a dynamic control triggering (1) mass-wasting processes upslope, as well as, down the slope, (2a) rapid flow transformation and efficient dilution (e.g., [START_REF] Fisher | Flow transformations in sediment gravity flows[END_REF][START_REF] Strachan | Flow transformations in slumps: a case study from the Waitemata Basin, New Zealand[END_REF]) resulting into fast-moving multiphase debris flows (e.g., [START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF][START_REF] Mohrig | Hydroplaning of subaqueous debris flows[END_REF][START_REF] Sohn | Transition from debris flow to hyperconcentrated flow in a submarine channel (the Cretaceous Cerro Toro Formation, southern Chile)[END_REF]) and (2b) coeval remobilization (soft-sediment translation and deformation) of the previously deposited, unlithified mass-flow deposits (e.g., Maltman 1994) (Figure 15B; Figure 16).

The MTDs' succession and the variations in slope gradient recorded throughout can therefore be used as a proxy for the tectonic activity of an individual structure. Here, they inform that at least six main tectonic pulses with uplift affected the structurally-controlled shelf-margin(s), each respectively generating one to several coalescing debris flows. Towards the top of the MTDs' succession, the high amount of sheared debris flow deposits, contorted strata, and the increasing bed dip variations (Figure 9) suggest both steep slope gradients (e.g., [START_REF] Postma | Classification for sediment gravity-flow deposits based on flow conditions during sedimentation[END_REF]) and an acceleration of the ridge activity. Steep, rising slopes, recurrently loaded with sediments, are unstable [START_REF] Hein | Geotechnical aspects of fine-grained mass flow deposits: California Continental Borderland[END_REF] and thus likely provided the right settings for locally triggering the failure of the entire MTDs' series as previously observed at Homewood (Figure 9; Figure 15). In this study, the high variability encountered within one intra-slope basin in terms of sediment delivery systems as well as transport and depositional processes highlights the role and importance of varying structural settings of the sediment source for controlling the subsequent deep-marine depositional settings. Despite similar source environments (i.e., mixed siliciclastic-carbonate shelves) developed atop the basin-bounding structures (i.e., thrust) along with comparable sediment delivery systems (i.e., slope channel and remobilization) and nature of flow processes (i.e., gravity-driven), the resulting shelf-derived deposits downslope are characterized by contrasting lithofacies assemblages, sizes and geometries.

Notwithstanding the size and extent of the catchment area or continental connection (attached or detached) as critical controls [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF], we here suggest that along active margins, the geometry and activity of the underlying structures (thrust forelimb and backlimb settings) at the shelf edges also greatly influence the resulting sediment distribution and architecture.

The shelf-edges on the forelimbs of underlying thrusts are abrupt, generally associated with steep, irregular and tectonically-controlled slope profiles [START_REF] Naranjo-Vesga | Regional controls in the distribution and morphometry of deepwater gravitational deposits along a convergent tectonic margin[END_REF]. Erosion and transport capacities proportionally increase with slope gradient and thus favor significant sediment bypass to the deeper settings [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF][START_REF] Crisóstomo-Figueroa | A new modelling approach to sediment bypass prediction applied to the East Coast Basin, New Zealand[END_REF]. Here, the tectonic activity at the shelf edges generally favored the development of systems that dynamically interact and rejuvenate the slopes (e.g., Waikaraka retrogressive system or Sefton Hills repeated collapse events (Claussmann et al. 2021)) and the resulting gravity-driven systems are generally hundreds of meters thick and several kilometers wide, preferentially transporting sediments through sediment gravity flows.

Conversely, thrust backlimb commonly provide longer and gentler slope gradients upon which a more gradual shelf edge transition may be expected and may facilitate the development of less efficient depositional systems [START_REF] Sømme | Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems[END_REF]. In this study however, these settings were connected to limited catchment areas (e.g., isolated island), thereby preventing the development of particularly large systems that typically occur on gentler slopes. Therefore, despite similar delivery systems to those associated to forelimb-related slopes (e.g., slope channels and destabilization), their sizes were largely smaller (tens of meters thick). or high sedimentation rates [START_REF] Moscardelli | New classification system for mass transport complexes in offshore Trinidad[END_REF][START_REF] Posamentier | The Character and Genesis of Submarine Mass-Transport Deposits: Insights from Outcrop and 3D Seismic Data[END_REF][START_REF] Moscardelli | Morphometry of mass-transport deposits as a predictive tool[END_REF]. As discussed here however, along active margins, shelfal environments not only develop in the submerged prolongation of the main hinterland, constituting continent-attached shelves, which can source large-scale shelf-derived mass-wasting products (e.g., [START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF]. Shelfal environments can also form episodically upon and around structurally controlled and active ridges, resulting in shelves that are detached from the main shelf domain (e.g., Ćosović et al. 2018). These isolated settings, with a virtually absent to limited catchment area (whether underwater or emerged), feature reduced shelfal source systems, which will, in turn, produce significantly smaller shelf-derived mass-wasting products such as the ones described at Homewood. The size of the resulting deposits best compares to those commonly found in detached MTDs (sensu Moscardelli and Wood 2015) (Appendix 6) whereas their internal characteristics inform that tectonic acted as the main triggering mechanism and that the source was nearby.

Notwithstanding sea-level changes and high sedimentation rates as causal mechanisms for shelf-derived mass-wasting events [START_REF] Posamentier | Deep-Water Turbidites and Submarine Fans[END_REF][START_REF] Moscardelli | New classification system for mass transport complexes in offshore Trinidad[END_REF]Moscardelli and Wood 2015; and references within), [START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF] and [START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF] previously demonstrated that along active margins, periods of tectonic activity (ca. 1 to 2 Ma) constitute another mechanism to consider for both the development and subsequent shelf failures. The MTDs described in this study not only provide another example of such shelf-derived mass-wasting products, whereby tectonic activity controlled the repeated destabilization and collapses of the shelfal source (see also [START_REF] Romero-Otero | Detached and Shelf-Attached Mass Transport Complexes on the Magdalena Deepwater Fan[END_REF][START_REF] Ortiz-Karpf | Mass-transport complexes as markers of deep-water fold-andthrust belt evolution: insights from the southern Magdalena fan, offshore Colombia[END_REF]), but also indicate that shelf-derived mass-wasting events do not always result in large-scale systems (Appendix 6) (see also [START_REF] Claussmann | Shelf-derived masstransport deposits: origin and significance in the stratigraphic development of trench-slope basins[END_REF].

Similarly, [START_REF] Naranjo-Vesga | Regional controls in the distribution and morphometry of deepwater gravitational deposits along a convergent tectonic margin[END_REF] observed that owing to the complex relationships that exist between the shelf width, slope profile and sediment supply in an analogous convergent setting (i.e., southern Caribbean fold-and-thrust belt), both attached and detached MTDs could be sourced from the regional shelf and slope regions.

Therefore, we here propose to slightly amend the MTD nomenclature from [START_REF] Moscardelli | New classification system for mass transport complexes in offshore Trinidad[END_REF] and [START_REF] Moscardelli | Morphometry of mass-transport deposits as a predictive tool[END_REF] by using the related 'attached' and 'detached' morphometry characteristics independently from the type (e.g., shelf, slope, local bathymetric highs) and distance from source areas to better account for the variety of geotectonic settings (e.g., convergent).

As a result, we introduce the term 'shelf-derived systems' which refers to all the MTDs that result from the destabilization and collapses of shelfal environments, whether induced by regional and or local causal mechanisms (sea-level changes, high sedimentation rates, periods of repeated tectonic activity, etc.),

  formed in response to the Uppermost Oligocene-to-Recent westward subduction of the Pacific Plate beneath the Australian Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

  Claussmann et al. (2021) previously demonstrated that short-lived periods (ca. 1 to 2 Ma) of sustained (with or without phases of quiescence) compressional tectonics favor the propagation of the folds and thrusts, and thus the expansion of abrupt, unstable areas close to these structurally-controlled shelfmargins. Repeated uplift and slope oversteepening of these areas eventually lead to recurrent shelf collapses, sourcing shelf-derived sediments (e.g., mass-wasting products) into deep water. The associated deposits result from sediment gravity flows, such as cohesive debris flows or mudflows, and Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

Figure 2 :

 2 Figure 2: [previous page] Chronostratigraphic chart for the southern, emerged portion of the Hikurangi subduction wedge adapted from Claussmann et al. (2021). Lithostratigraphy details adapted from[START_REF] Chanier | Discovery of Pithonellids in the Upper Cretaceous of New Zealand; biogeographic, stratigraphic and tectonic consequences[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF], Chanier

Figure 3 :

 3 Figure 3: Satellite map from World Imagery (ESRI), and onshore geological map from Chanier (1991) of the Whareama Basin. Location of the drone acquisition and related 3D outcrop models presented in this study = wk = Waikaraka section and hw = Homewood section. See Claussmann et al. (2021) for the s-1 and s-2: Sefton Hills section and 3D outcrop model.

  These comprise massive silty mudstones (MDST); tabular, very thin-to medium-bedded (LDTC-a) or medium-to thick-bedded (LDTC-b) sandstones with mudstone caps; lenticular, medium to very-thick bedded sandstones (HDTC); structured (SST-a) or structureless (SST-b) sandstones; pebbly sandstones (sHDTC-a); bioclastic grits (sHDTC-b); lenticular, medium to very-thick bedded gravel sandstones with mudstone caps (gsHDTC); organized to disorganized clast-supported (respectively gHDTC, CF) and matrix-support (DF) conglomerates; as well as deformed (SL-a) or undeformed (SL-b) mass of sediments. Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

Figure 4 :

 4 Figure 4: Representative photographs of the lithofacies summarized inTable 1 and recognized at Waikaraka. Scales: human

Figure 5 :

 5 Figure 5: Representative photographs of the lithofacies summarized inTable 1 and recognized at Waikaraka. Scales: human

Figure 7 :

 7 Figure 7: Representative photographs of the lithofacies summarized inTable 1 and recognized at Homewood. Scales: human

Figure 8 :

 8 Figure 8: 3D outcrop model (top) and interpretation (bottom) of the Waikaraka coastal outcrop that exposes a confined slope channel system (Fa2c). This system comprises two distinct channel complexes, essentially divided into early-stage confined channel fills (Fa2c-e) and late-stage confined channel fills (Fa2c-l). The letters refer to remarkable architectural elements that characterize the Waikaraka system: a detailed view and explanation of each of them is available in Figure10. The colors used in the stereoplots correspond to the location circles presented on the

Figure 10 :

 10 Figure 10: [previous page] Detailed views of the shelf-derived gravity-driven deposit main architectural and sedimentaryelements supporting the interpretation of the Waikaraka 3D outcrop model (Figure8). Fa2c corresponds to the confined slope channel system facies association, whereby Fa2c-e means early-stage fills and Fa2c-l late-stage fills. CF, DF, gHDTC, gsHDTC, SST, HDTC, LDTC correspond to the lithofacies summarized in Table1. (a): Discontinuity D5 from Bailleul et al. (2007) and Bailleul et al. (2013) marking the transition from Fa2c-e to the uppermost sand-rich deposits; (b, e): Fa2c-l finingand thinning-upward conglomerate (gHDTC, gsHDTC) to sandstone series (HDTC, LDTC) overlain by Fa2c-e amalgamated conglomerates (CF and gHDTC) then followed by sandstones (HDTC, LDTC); (c): Fa2c-l boulder-grade clast imbrication (base of gsHDTC); (d): Fa2c-l three successive channel storey fills characterized by conglomerate-rich bases (gsDHTC) with upward (e.g., flame) and downward (e.g., load) soft-sediment features, overlain by sandstone-rich lithofacies (HDTC to LDTC); (f, h): Fa2c-l amalgamated, broadly lenticular channel storey fills (gsHDTC, HDTC, LDTC) ; (g): Fa2c-l upward (e.g., flame) soft-sediment features and trough cross stratifications; (i): Fa2c-e transitioning to Fa2c-l; (j): Fa2c-e amalgamated sandstones (HDTC) pinching out to the north overlaid by the Fa2c-e conglomerates (DF, CF); (k): large-scale fluid escape structures and downward (e.g., load) soft-sediment features in the Fa2c-e sandstones series (HDTC, LDTC) that underlies the next Fa2c-e conglomerate events (DF, CF); (l): Fa2c-e amalgamated conglomerates with outsized clasts (CF).

Figure 11 :

 11 Figure11: Sedimentary sections recorded at the Waikaraka outcrop. This system comprises two distinct channel complexes, respectively divided into the early-stage confined channel fills (Fa2ce) and late-stage confined channel fills (Fa2c-l). The letters in dark red refer to remarkable architectural elements that characterize the Waikaraka system: a detailed view and explanation of each of them is available in Figure10. The letters and numbers in blue give the location of the clast analyses summarized in Figure13. Details on the sample data are available in Appendix 2. The red surface named D5 at the top of the Waikaraka fill corresponds to the discontinuity D5 from[START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF] and[START_REF] Bailleul | Neogene evolution of lower trench-slope basins and wedge development in the central Hikurangi subduction margin[END_REF], which marks the transition to the period of generalized subsidence that affected the Hikurangi Margin during the Middle Miocene, Waiauan.

Figure 12 :

 12 Figure 12: [previous page] Detailed views of the shelf-derived gravity-driven deposit main architectural and sedimentary

  (a, b): Fa3p succession of interbedded conglomerates (DF, CF) recurrently capped by sandstones (SST) and overlain by the onlapping Fa1g sandstones (HDTC, LDTC); (b): Fa3p varying bed dips and upper contorted unit; (c, d, e, g, h): Fa3p conglomerates showing local variation in clast concentrations at their base, edge and or top (sheared DF), (d, h): Fa3p sharp surface at the base of the succeeding conglomerate, which holds contorted sandstones; (e): Fa3p occurrence of clast-poor conglomerate (DF) and upper contorted unit; (f, i, j): Fa3p contorted conglomerates (SL-a, made of DF, CF and SST); (g, h): Fa2c crude fining-and thinning-upward conglomerate to sandstones (gHDTC, sHDTC, LDTC), overlain by Fa3p, which is characterized by erosion as well as local substrate entrainment and deformation at its base; (i, j): Fa3p basal eroded through Fa2c towards the north-east.

  , we here suggest a different mechanism to explain the deformation recorded at the unit-scale and propose that a change in slope gradient can both trigger development of a mass flow upslope and coeval remobilization (translation and deformation) of the previously deposited and only poorly lithified mass-flow deposits downslope. When combined with bed dips, the analysis of the fold hinges and axial planes at both clastand unit-scales consistently indicates a NW-dipping paleoslope and transport direction (Alsop et al. 2019; Alsop and Weinberger 2020), coherent with a rising structure to the east. The larger-scale remobilization observed to the north-east that involves the entire facies association Fa3p could also be associated with this growing structure. As such, we interpret it to result from local failure of the entire series due to the recurrent loading of sediments onto this rising slope, two mechanisms known Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

  remobilizing sub-angular to sub-rounded, pebbles to outsized clasts (deci-to decametric) from the entire Lower Cretaceous to Paleocene pre-subduction series at their base. Interestingly, sub-rounded to rounded, granule-to pebble-grade Lower Cretaceous clasts are also occasionally observed throughout Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

  , eight distinct varieties of shell bed clasts are observed (Appendix 5), which are often of cobble-to bouldergrades in the early-stage fills (Fa2c-e). Thick-shelled Molluscan remains are frequent in the shell bed clasts (Appendix 5, A-F, H), along with well-rounded lithic pebbles commonly bearing the trace fossil Gastrochaenolites (Appendix 5, B-D). The overall faunal assemblages, including Struthiolaria sp., Polinices sp., Oysters, Turritellids, Serpulids and zooxanthellate corals (Appendix 5), and moderate degrees of pre-burial taphonomic alteration collectively point to rapid deposition in high-energy proximal inner-shelf to middle-shelf environments. Conversely, shell bed clasts are only punctually found (<0.5%)in the confined slope channel (Fa2c) and mass-wasting system (Fa3p) of Homewood. They however only comprise pebble-to cobble-grade skeletal and bioclastic fine-grained sandstones dominated by turritellid gastropods (cf. facies Fa6c from[START_REF] Bailleul | Turbidite Systems in the Inner Forearc Domain of the Hikurangi Convergent Margin (New Zealand): New Constraints on the Development of Trench-Slope Basins[END_REF]).

Figure 15 :

 15 Figure 15: (A): Schematic NW-SE cross-section through the subduction-related, compressive Whareama intra-slope basin (i.e., trench-slope basin) during the Middle Miocene. The depositional settings for the forelimb and backlimb settings of actively growing thrust-cored structures are highlighted. (B): Schematic representation of the inferred shelf-derived gravity-driven systems and processes related to the forelimb and backlimb settings.

  Seven samples were collected to supplement the Fossil Record Electronic Database (https://fred.org.nz/) since both areas are currently mapped as Quaternary beach deposits on the 1:250 000 Geological Map of New Zealand (QMAP) of Wairarapa (https://www.gns.cri.nz/). The micro-and macropaleontological analyses were conducted by GNS New Zealand and allowed to determine the age of the sedimentary units and related depositional paleobathymetries (Appendix 2; Appendix 3).

	Digital fieldwork involved the acquisition of high-resolution aerial images (1,900 at Waikaraka and 690 at
	Homewood) using a DJI Phantom 4 Pro drone, supplemented by a number of Ground Control Points
	(GCP) collected with a Trimble GeoExplorer 2008 differential global positioning system tool (DGPS) and
	a Trimble Tempest antenna positioned at two meters above the measured point. Two georeferenced 3D

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Table

Table

Table

Fa1g refers to Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

  and Claussmann et al. (2021), in which

Table

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	marked by subtle variations in clast grade and alignment, or in matrix concentration (DF) to (2) being
	internally organized, displaying inverse-to normally-or only normally-graded patterns (gHDTC) (Figure
	). The conglomerates
	essentially evolve from (1) being internally disorganized (CF), only comprising local internal stratifications,

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22 Accepted Manuscript version. Published Journal Article version available online, published by Elsevier in Marine and Petroleum Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252

  Figure14: Taphonomic characterization of fossil remains described from one square meter area of outcrop at Waikaraka and Homewood, using frequency histograms of the degree of alteration (e.g., low, moderate, high, very high) for each category of skeleton damage (i.e., fragmentation, abrasion, bioerosion) and encrustation. Lithofacies CF, DF, gHDTC and gsHDTC are described in details in Table1and facies associations Fa2c and Fa3p in Section 5.

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  , which indicate the nearby presence and connection with exhumed land. Also, the occurrence of subrounded lithoclasts can suggest a fluvial and or shallow-marine origin with extraformational clasts that

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2021.105252 being

  otherwise dominated by Upper Cretaceous strata (seeSection 6.3). Although direct erosion of the exhumed Cretaceous basement likely acted as an additional source, we attribute the former clast content to chiefly result from CSCS forming processes, such as initial slope failure (e.g.,[START_REF] Janocko | The diversity of deep-water sinuous channel belts and slope valley-fill complexes[END_REF]

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2021.105252 7.3. Generic implications 7.3.1. For shelf-derived gravity-driven systems sourced from thrust forelimb and backlimb

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ACKNOWLEDGEMENTS

This research was funded by Schlumberger. We are grateful to Karen and John Barbour for their warm welcome during our stays at Homewood and for access to the studied areas. Special thanks to Pierre Malié and Andréa Barrier for their support during the fieldwork missions, as well as to Romain Armand, François-Xavier Joanny and Pierre Saulet from UniLaSalle (France) for their technical assistance on the GIS and outcrop modelling workflows. We also thank our colleagues from the Basins-Reservoirs-Resources B2R research unit (University of UniLaSalle, France) for their lasting support and Hugh Morgans and Henry Gard from GNS Science (Lower Hutt, New Zealand) for the paleontological analyses.

Finally, we thank the Editor Roberto Tinterri and the reviewers, Bradford Prather and Domenico Chiarella for their helpful and constructive comments and suggestions. GNS Science GNS Science GNS Science GNS Science GNS Science GNS Science GNS Science GNS Science Foraminifera

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Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252 Figure 6: Representative photographs of the lithofacies summarized in Table 1 and recognized at Homewood. Scales: human size (~1.70 meters); Jacob's staff (1.5 meter); hammer (33 centimeters); card (8.5 centimeters long); coin (2.3 centimeters).

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Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252 developed upon and around a structurally-controlled ridge located to the east of Homewood, which was detached from the regional shelf and hinterland (Figure 15A). Isolated platforms may develop above fault-growing folds and favor biogenic carbonate production as they lack continent-derived siliciclastic inputs [START_REF] Caron | Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand[END_REF][START_REF] Ćosović | Development of transient carbonate ramps in an evolving foreland basin[END_REF][START_REF] Caron | Episodes of seabed rise and rapid drowning controlling the development of regressive and transgressive rhodolithic limestones in a tectonically-active subduction setting (Early Miocene, Wairarapa region, New Zealand)[END_REF].

At Homewood however, analyses of the reworked material (see Section 6) inform that mixed siliciclasticcarbonate sediments dominated, thereby suggesting both emergence and subsequent erosion of the uplifted ridge (Figure 15A; Figure 16). Previous work highlighted that islands developed above tectonically-controlled topography can supply terrigenous material (e.g., McArthur et al. 2016a) and result in mixed siliciclastic-carbonate sedimentation (e.g., Chiarella et al. 2012;Chiarella and Longhitano 2012;[START_REF] Ćosović | Development of transient carbonate ramps in an evolving foreland basin[END_REF].

More particularly, the nature of the deposits (i.e., Fa2c and Fa3p slope deposits) and their clasts (see Part 5) suggests that the ridge was nearby and exhumed for some time to allow (1) the dismantlement of the pre-subduction series down to the Upper Cretaceous strata, ( 2) their subsequent reworking in the littoral domain and (3) the formation of sandy shell beds. Notwithstanding submarine erosion, the abundance of sub-rounded clasts of Upper Cretaceous strata implies that these strata likely outcropped at the time (e.g., Di [START_REF] Celma | Sedimentology, architecture, and sequence stratigraphy of coarse-grained, submarine canyon fills from the Pleistocene (Gelasian-Calabrian) of the Peri-Adriatic basin, central Italy[END_REF], thereby inferring initial rise and emergence of the ridge prior to the Middle Miocene, Upper Clifdenian to Lower Lillburnian (Langhian, 15.9 -14 Ma, Appendix 2).

When combined, the pre-subduction Paleogene cover, about 600 meters thick in the study area [START_REF] Van Den Heuvel | The geology of the flat point area, eastern Wairarapa[END_REF][START_REF] Chanier | Le prisme d'accrétion Hikurangi: un témoin de l'évolution géodynamique d'une marge active pacifique[END_REF][START_REF] Chanier | From a passive to an active margin: Tectonic and sedimentary processes linked to the birth of an accretionary prism (Hikurangi Margin, New Zealand)[END_REF], and the general exhumation rate of up to 0.3 kilometer/million year calculated by [START_REF] Jiao | Thermal history and exhumation of basement rocks from Mesozoic to Cenozoic subduction cycles, central North Island, New Zealand[END_REF] along the eastern North Island of New Zealand indicate that the ridge emergence (i.e., island setting) and subsequent erosion started at least ca. 2 Ma prior to that time. This ridge likely corresponded to the seaward margin of the Whareama Basin, structurally controlled by the underlying seaward-verging Flat Point-Whakataki Fault complex and located to the east of Homewood (i.e., Glenburn Nappe) (e.g., Chanier 1991) (Figure 3; Figure 15A). The set of morphometric relationship equations calculated by [START_REF] Moscardelli | Morphometry of mass-transport deposits as a predictive tool[END_REF] predicts a length of about two kilometers for the MTDs (Appendix 6), which may or may not include the evacuation area (sensu [START_REF] Moscardelli | Morphometry of mass-transport deposits as a predictive tool[END_REF] yet provides a broad insight as to the potential distance to the ridge at the time (less than two kilometers). The envisaged shelfal system was narrow and located on the western side of the island, upon the backlimb of the underlying asymmetrical thrust (Figure 15A; Figure 16). Similarly, the mixed siliciclasticcarbonate Fingerpost shelf developed further north during the Early to Middle Miocene; it was also positioned to the west of an emergent landmass (i.e., the Cape Turnagain Structural High), itself Destabilization and collapses of the mixed siliciclastic-carbonate shelfal sources occurred on both sides of the basin-bounding structures and thus indicate that any of these shelves, either attached to the main continental domain or detached from it (e.g., isolated island) can be subjected to shelf-derived sediment mass movement and mobilization (sensu [START_REF] Iverson | The physics of debris flows[END_REF].

When sourced from the backlimb of an actively growing structure (i.e., thrust) however, the mass-wasting deposits exhibit more complex internal architectures, clearly recording the slope gradient variations and resulting in intricate interactions between mass movements and mass flows, such as the ones observed at Homewood. The changes in slope gradient will dynamically control both (1) the generation of mass movements and flows upslope, and ( 2) the coeval remobilization (e.g., sliding) and soft-deformation (e.g., slumping) of the previously deposited, poorly-lithified sediments (e.g., debrites) downslope. Conversely, although mass movement (e.g., slide, slump) can undoubtedly occur as well, the MTDs sourced from the forelimb of an actively growing structure (i.e., thrust) seem primarily characterized by a series of coalescing mass-flow deposits (e.g., debris flows) (e.g., Festa et al. 2010 and references therein). Mass movements either seem preferentially recorded close to the source region or at the base of the MTDs' sequence, where they often result from soft-sediment deformations (e.g., slide, slump) of the unlithified sediments that were previously deposited at the front of the rising structure (e.g., [START_REF] Festa | Mélanges and mélange-forming processes: a historical overview and new concepts[END_REF][START_REF] Lackey | Tectonic Influences on Trench Slope Basin Development via Structural Restoration Along the Outer Nankai Accretionary Prism[END_REF].

Overall, the shelf morphology (i.e., narrow), extent (e.g., regional or isolated), continental connection (e.g., attached or detached), sediment type (i.e., mixed siliciclastic-carbonate sedimentation) as well as the respective geotectonic settings (e.g., upon and around the forelimb or backlimb of the underlying thrusts and fault-growing folds) all chiefly controlled the architecture and subsequent shelf-derived deposits. However, along tectonically-active margins, when sourced from mixed siliciclastic-carbonate systems, the deep-marine, shelf-derived deposits seem characterized by tens to a few hundred of meters of thickness and several kilometers of lateral extent. The durations of the associated depositional systems are from 1 to 2 Ma, being controlled by the structural styles and local tectonic activity at the source rather than regional-scale variations. [START_REF] Moscardelli | Morphometry of mass-transport deposits as a predictive tool[END_REF] have proposed differentiating mass-wasting products into attached and detached systems, respectively sitting in a proximal and a distal position from any shelf break, and either sourced from this regional area (e.g., shelf) or local structures. 16). Similar reasoning can be applied to the MTDs that result from failures of the regional slope (i.e., 'slope-derived systems').

For mass-transport deposit nomenclature

Notwithstanding the slope profile, here inherently linked to the geometry of the underlying structural styles at the source (e.g., forelimb or backlimb) and the sediment supply as other critical parameters (e.g., [START_REF] Naranjo-Vesga | Regional controls in the distribution and morphometry of deepwater gravitational deposits along a convergent tectonic margin[END_REF], the present study demonstrates that the geomorphology of source area, and more particularly its connection to the continent (i.e., catchment area) is also critical. Here, the narrow shelves appear to source both 'attached and detached shelf-derived systems' when connected to the main hinterland (narrow continent-attached shelf) and 'detached shelf-derived systems' when isolated and disconnected from it (narrow continent-detached shelf) (Figure 16). Further work is however required to generalize such an observation; and more particularly, the impact of the forelimb settings on the resulting shelf-and slope-derived mass-wasting systems (e.g., size, internal characteristics, causal mechanisms) sourced from continent-detached mixed siliciclastic-carbonate shelfal domains remains to be investigated.

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CONCLUSIONS

In this study, we used high-resolution outcrop data to investigate the implications of mixed siliciclasticcarbonate source systems developed upon and around the forelimbs and backlimbs of actively growing asymmetrical structures for the development of the subsequent gravity-driven systems beyond the shelf edges. Particularly, this study highlights the role and importance of varying structural setting of the sediment source in controlling the morphologies of the delivery systems, the patterns of sediment dispersal, and the related sedimentary facies along active margins.

First, we demonstrated that during the Middle Miocene, the paleogeography of the southern, inner portion of the Hikurangi Margin was diversified, comprising a mature hinterland to the west as well as isolated islands to the east, developing atop the actively growing seaward-verging thrusts of the subduction wedge. Mixed compositional siliciclastic-carbonate sedimentation dominated at shallow depths and the different morphologies of the source regions (continent-attached, forelimb and continent-detached, backlimb) resulted in the development of highly varied shelf-derived gravity-driven systems downslope within very short distances (less than five kilometers) that interacted with the structures and were eventually captured both on their margins and within the trench-slope basins.

Then, we showed that mixed siliciclastic-carbonate gravity-driven systems in active settings appear preferentially characterized by deposition of tens to a few hundred of meters of thick units, displaying several kilometers of lateral extent, for duration of ca. 1 to 2 Ma. Such systems are primarily controlled by the geometries and tectonic motion of the underlying structures at the shelf edges. Different morphologies of the source regions (i.e., the aforementioned continent-attached forelimb and continentdetached backlimb of thrust settings) result in the development of distinct paleoenvironmental conditions at the shelf and contrasting shelf-derived gravity-driven systems along and downslope. The shelf-edges on the forelimbs of actively growing thrusts are abrupt and commonly associated with irregular steep slopes. Here, they appear to have favored the development of systems that dynamically rejuvenate the slopes (e.g., Waikaraka retrogressive systems). On the backlimbs however, the shelf-edges are generally associated to gentler slopes; yet, pulses in tectonic activity will increase slope gradient variations, thus promoting the development of sedimentary systems that directly interact with the slope (e.g., Homewood mass-wasting system).

Finally, this study highlights that, whether they are caused by regional and or local triggering mechanisms, the destabilization and collapses of shelfal environments source 'shelf-derived mass-wasting systems', characterized by two types: (1) large-scale, regional 'attached shelf-derived systems' and (2) small-scale,

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Geology Journal: https://doi.org/10.1016/j.marpetgeo.2021.105252 localized 'detached shelf-derived systems'. Along active margins, and particularly the Hikurangi Margin, the 'shelf-derived mass-wasting systems' are sourced from shelves that are either attached to the main continental domain or detached from it (e.g., isolated islands). The associated shelf-derived masswasting deposits can be found on both sides of actively growing asymmetrical thrusts. When sourced from the backlimbs however, the subsequent shelf-derived MTDs exhibit more complex internal architectures, ultimately recording the dynamic changes in slope gradient, which can both trigger the generation of mass failures and mass flows upslope as well as the coeval remobilization (translation and deformation) of the previously deposited MTDs downslope. As a result, the MTDs from thrust backlimbs can be used as proxies for unraveling the tectonic activity of an individual structure. Qualitative taphonomic grading system established for the two dominant categories of fossil remains found in the studied deposits, namely Gastropods and Bivalves. The scales of alteration features were established to help characterize poorly to very highly damaged grains at outcrop. The particle contours displayed derive from field observations. The degree of abrasion was determined using the visual chart of [START_REF] Powers | A new roundness scale for sedimentary particles[END_REF]. The scale of skeleton bio-infestation is modified from [START_REF] Perry | Grain susceptibility to the effects of microboring: implications for the preservation of skeletal carbonates[END_REF]. Appendix 4: Enlarged view of the Homewood outcrop, mostly comprising a several hundreds of meter-thick distal depositional lobe system (Fa1g). This study particularly focuses on the gravity-driven systems present at the base of this series and which are presented in the detailed view of the outcrop model in Figure 9.

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