M Mojtahid
email: meryem.mojtahid@univ-angers.fr

Elisabeth Michel

P De Deckker

From "source to sink" -A new perspective on the past dynamics of the Murray Canyon Group from benthic foraminiferal communities

Keywords: Turbidites, Last Glacial, River Murray, Bouma-like sequence, Shelf foraminifera, Bathyal foraminifera, Abyssal foraminifera

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

Introduction

Submarine canyons are steep-sided valleys on continental margins and play a major role as conduits to the deep sea for sediment and organic material from the continental domain, as well as from slope and shelf (e.g. [START_REF] Shepard | Submarine canyons[END_REF][START_REF] Weaver | Continental margin sedimentation, with special reference to the north-east Atlantic margin[END_REF][START_REF] Mulder | Understanding continent-ocean sediment transfer[END_REF][START_REF] Allen | A review of the role of submarine canyons in deep-ocean exchange with the shelf[END_REF][START_REF] Quattrini | Exploration of the Canyon-Incised Continental Margin of the Northeastern United States Reveals Dynamic Habitats and Diverse Communities[END_REF]. The major mechanism of canyon erosion is believed to be turbidity currents (e.g. Bouma et al., 1985;[START_REF] Azpiroz-Zabala | Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons[END_REF]. These dense sediment-laden currents flow downslope when an unstable upper slope mass of sediment fails under the influence of climatic factors (e.g. sea-level changes, high river discharge, marine currents, coastal storms) and non-climatic factors (e.g. earthquakes, tsunamis, volcanic eruption, storm surges, release of gas hydrates) (e.g. [START_REF] De Garidel-Thoron | Evidence for large methane releases to the atmosphere from deep-sea gas-hydrate dissociation during the last glacial episode[END_REF][START_REF] Piper | Processes That Initiate Turbidity Currents and Their Influence on Turbidites: A Marine Geology Perspective[END_REF][START_REF] Bernhardt | Shelfal sediment transport by an undercurrent forces turbidity current activity during high sea level along the Chile continental margin[END_REF]. These phenomena are generally identified in marine sediment cores as Bouma-like turbiditic sequences [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF]. Because of rapid organic material transport down slope, turbidity currents funneled through canyons very likely enhance marine biodiversity, especially in the deep-sea (e.g. [START_REF] Mcclain | Habitat heterogeneity, disturbance, and productivity work in concert to regulate biodiversity in deep submarine canyons[END_REF][START_REF] Fernandez-Arcaya | Ecological Role of Submarine Canyons and Need for Canyon Conservation: A Review[END_REF], and constitute "accelerators" for carbon sequestration (e.g. [START_REF] Schlünz | Transport of terrestrial organic carbon to the oceans by rivers: re-estimating flux-and burial rates[END_REF][START_REF] Galy | Efficient organic carbon burial in the Bengal fan sustained by the Himalayan erosional system[END_REF]. Much progress has been made in describing the morphology of submarine canyons at high spatial resolution, mainly because of the considerable advances in imaging using the latest generation of multibeam technology (e.g. [START_REF] Hill | Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin[END_REF][START_REF] Lastras | Geomorphology and sedimentary features in the Central Portuguese submarine canyons, Western Iberian margin[END_REF][START_REF] Mountjoy | Morphostructure and evolution of submarine canyons across an active margin: Cook Strait sector of the Hikurangi Margin[END_REF][START_REF] Paull | Origins of large crescent-shaped bedforms within the axial channel of Monterey Canyon, offshore California[END_REF]. An important gap remains, however, in our understanding of the processes that shape these submarine canyon systems, and how they respond to climatic and non-climatic influences.

In particular, the source and the triggering origin of turbidity currents are still a matter of debate (e.g. [START_REF] Piper | Processes That Initiate Turbidity Currents and Their Influence on Turbidites: A Marine Geology Perspective[END_REF][START_REF] Covault | Submarine fans at all sea-level stands: Tectonomorphologic and climatic controls on terrigenous sediment delivery to the deep sea[END_REF]. One way to address this issue is to investigate the processes that control fluvial/canyon connections recorded in marine sediment cores during the Quaternary geological period modulated by glacial/interglacial cycles under contrasting sea-level stands and climatic conditions (e.g.

Lombo [START_REF] Lombo Tombo | Sea-level control on turbidite activity in the Rhone canyon and the upper fan during the Last Glacial Maximum and Early deglacial[END_REF][START_REF] Mauffrey | Sea-level control on the connection between shelf-edge deltas and the Bourcart canyon head (western Mediterranean) during the last glacial/interglacial cycle[END_REF].

Fossil benthic foraminiferal faunas preserved in deep-sea Quaternary sediment cores at the outlet of canyons are good candidates to record changes in depositional environments and palaeo-water depths. Foraminifera have previously been used to assist in identifying and determining the provenance of Late Quaternary turbidites (e.g. [START_REF] Strachan | Non-cohesive silt turbidity current flow processes; insights from proximal sandy-silt and siltysand turbidites, Fiordland, New Zealand[END_REF][START_REF] Hayward | Benthic foraminifera and the late Quaternary (last 150 ka) paleoceanographic and sedimentary history of the Bounty Trough, east of New Zealand[END_REF][START_REF] Hayward | Using foraminiferal test-size distribution and other methods to recognise Quaternary bathyal turbidites and taphonomically-modified faunas[END_REF]. In order to assign a depth range to a species in the fossil record, we often rely on studies of modern settings where bathymetry and associated environmental parameters are accurately measured. These bathymetric intervals are then applied on a generic level to the fossil record (e.g. [START_REF] Schröder-Adams | Influence of sediment transport dynamics and ocean floor morphology on benthic foraminifera, offshore Fraser Island, Australia[END_REF]. When determining palaeo-depths, it is fundamental to distinguish autochthonous from transported (allochthonous) faunal taxa since gravity processes frequently transport benthic foraminifera from the inner continental shelf to the abyssal plain together with sediment particles. The foraminifera tests may suffer abrasion or dissolution when transported and deposited close to or below the Calcite Compensation Depth (CCD).

Here, we investigate the past (~40 to 12 ka) dynamics of one of the canyons in the Murray Canyon Group offshore Kangaroo Island (South Australia) using benthic foraminiferal assemblages from a 5,078 m-water depth sediment core (SS02/06-GC2) (Fig. 1). The existence of this major canyon system was first recognized by [START_REF] Sprigg | Newly Discovered Submarine Canyons of New Guinea and South Australia[END_REF] and, since then, several studies have been published, mainly after the two AUSCAN cruises in 2003and 2006(e.g. Gingele et al., 2004;;[START_REF] Hill | AUSCAN seafloor mapping and geological sampling survey on the Australian southern margin by RV Marion Dufresne in 2003: Final project report[END_REF][START_REF] Gingele | Late Quaternary fluctuations of palaeoproductivity in the Murray Canyons area, South Australian continental margin[END_REF][START_REF] Hill | Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin[END_REF][START_REF] Calvo | Antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore South Australia[END_REF][START_REF] Gingele | Late Pleistocene and Holocene climate of SE Australia reconstructed from dust and river loads deposited offshore the River Murray Mouth[END_REF][START_REF] Moros | Holocene climate variability in the Southern Ocean recorded in a deep-sea sediment core off South Australia[END_REF][START_REF] Schmidt | Are the Murray Canyons offshore southern Australia still active for sediment transport?[END_REF][START_REF] De Deckker | Influence of the tropics and southern westerlies on glacial interhemispheric asymmetry[END_REF][START_REF] Lopes Dos Santos | Late Quaternary productivity changes from offshore Southeastern Australia: A biomarker approach[END_REF], 2013;[START_REF] Bayon | Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings[END_REF][START_REF] Bayon | Preferential Riverine Export of Fine Volcanogenic Particles to the Southeast Australian Margin[END_REF]. Most of these studies tackled the recent morphobathymetric features and sedimentary processes of the canyons or investigated Late Quaternary environments using sediment cores away from the main turbidity pathways.

Yet, the origin of the canyon system itself is still largely unknown. Some canyons are thought to be related to ancient courses of the River Murray and could have provided a pathway during low sea levels to bring sediments from the River directly to the abyssal area [START_REF] Gingele | Late Quaternary terrigenous sediments from the Murray Canyons area, offshore South Australia and their implications for sea level change, palaeoclimate and palaeodrainage of the Murray-Darling Basin[END_REF]. These sediments flowing into the abyss for millions of years carry geochemical and palaeontological signatures of past climatic and environmental conditions. [START_REF] Hill | AUSCAN seafloor mapping and geological sampling survey on the Australian southern margin by RV Marion Dufresne in 2003: Final project report[END_REF] and [START_REF] Hill | Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin[END_REF] described the presence of large deep-water holes in the abyssal area, spaced about 5 km apart and up to several hundred meters deep (Fig. 1), that were interpreted as probably being gouged by surges of high-energy turbidity currents, which such steep canyons could generate. Core SS02/06-GC2 is located in one of these topographic depressions at one of the outlet channels of the larger and steeper canyons of the Murray Canyon Group (Fig. 1).

This study uses benthic foraminifera and sediment characteristics of the core to distinguish between displaced downslope and in-situ hemipelagic sediments, with the aim of identifying the provenance of the turbidites of Late Quaternary age. When comparing the palaeoecological interpretations obtained from the characterization of benthic foraminiferal communities with climatic and continental proxies from the existing literature in the area, we further aim at reconstructing the sedimentary imprints of the interplay between sea level and climatic changes, and their relative importance for triggering turbidity currents.

Study area

Gravity core SS0/06-GC2 (255 cm long; 37°07.980' S; 136°29.735' E) was sampled in March 2006 during the "AUSCAN 2006 and PALAEO-MURRAYS" cruise onboard the RV Southern Surveyor south of the upper Sprigg Canyon at the depth of 5,078 m (Fig. 1).

The Murray Canyon Group, located in the southeastern continental margin of Australia (Fig. 1a; b), are amongst the biggest canyon systems in the world (~5 km drop with up to 2 km high canyon walls). The continental shelf bordering the Murray Canyon Group is known as the "carbonate factory" because it is the largest region of cool-water carbonate sediment deposition in the modern world (e.g. [START_REF] James | Holocene carbonate sedimentation on the west Eucla Shelf, Great Australian Bight: a shaved shelf[END_REF][START_REF] James | Neritic Carbonate Sediments in a Temperate Realm: Southern Australia[END_REF][START_REF] James | The macroalgal carbonate factory at a cool-towarm temperate marine transition, Southern Australia[END_REF]. For this reason, seawater in this region is supersaturated with respect to both aragonite and calcite at least down to depths of 1,000 m [START_REF] James | Where Has All the Aragonite Gone? Mineralogy of Holocene Neritic Cool-Water Carbonates, Southern Australia[END_REF].

Cores from the southern Indian Ocean south of Australia show that the CCD lies at 4,800-4,900 m (Mallet and Heezen, 1977;[START_REF] Belyaeva | Critical carbonate levels in the Indian Ocean[END_REF]. This deep CCD explains the abyssal plain seabed sediments being mostly foraminifer-nannofossil ooze [START_REF] Feary | Geological Sampling in the Great Australian Bight: Scientific Post-cruise Report -R/V Rig Seismic Cruise 102[END_REF][START_REF] Dutkiewicz | Census of seafloor sediments in the world's ocean[END_REF], and the overall good preservation of foraminiferal tests in our sediment core.

The Murray Canyon Group is located off the Murray-Darling River mouth (referred to in this manuscript as the River Murray mouth for simplicity) [START_REF] Gingele | Late Quaternary fluctuations of palaeoproductivity in the Murray Canyons area, South Australian continental margin[END_REF], which is Australia's largest exorheic river system [START_REF] Bourman | Explaining the coastal landscapes of South Australia -A synthesis[END_REF] (Fig. 1a).

The modern discharge at the Murray mouth is highly dependent on rainfall intensity in the Murray-Darling Basin (e.g. Grafton et al., 2014). An average of 5,088.10 6 m 3 yr -1 (~160 m 3 s -1 ) was recorded during a relatively wet period on the continent while during the more recent dry years (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010), flows at the Murray Mouth dropped by about 96 % reaching an average of 190.10 6 m 3 yr -1 (~6 m 3 s -1 ) [START_REF] Grafton | Water Planning and Hydro-Climatic Change in the Murray-Darling Basin, Australia[END_REF].

Because the Murray mouth is presently ~200 km away from the canyons, little terrigenous material from the Murray Darling Basin reaches the study area and sediments consist mainly of pelagic carbonate particles and aeolian dust (e.g. [START_REF] Bayon | Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings[END_REF][START_REF] Bayon | Preferential Riverine Export of Fine Volcanogenic Particles to the Southeast Australian Margin[END_REF]. There is however evidence of some fluvial clays reaching the core sites during the last 6 ka, after the stabilization of sea level [START_REF] Gingele | Late Quaternary terrigenous sediments from the Murray Canyons area, offshore South Australia and their implications for sea level change, palaeoclimate and palaeodrainage of the Murray-Darling Basin[END_REF]. By using a multi-tracer approach ( 210 Pb and 230 Th) on interface sediments from the Murray canyons (350 -2500 m water depths), the study of [START_REF] Schmidt | Are the Murray Canyons offshore southern Australia still active for sediment transport?[END_REF] shows the presence of freshly deposited carbonate particles. This finding supports the occurrence of recent, significant advection of marine sediments, mostly from the shelf, within these canyons.

Because the entrance of the canyons start at around the 120 m isobath (Figure 1a, b), a larger fluvial sedimentary input to the deep-sea was present during minimum sea-level stands (during oxygen isotope stages 2, 4 and 6) as the Murray mouth was probably at the present shelf edge and almost directly connected to the canyons [START_REF] Gingele | Late Quaternary terrigenous sediments from the Murray Canyons area, offshore South Australia and their implications for sea level change, palaeoclimate and palaeodrainage of the Murray-Darling Basin[END_REF][START_REF] Hill | Ancestral Murray River on the Lacepede Shelf, southern Australia: Late Quaternary migrations of a major river outlet and strandline development[END_REF]. The well-defined 'glacial' channels (= formed during periods of low sea level) on the adjacent continental shelf show that the Murray River traversed the shelf from the location of its current mouth towards the submarine canyons south of Kangaroo Island [START_REF] Sprigg | Newly Discovered Submarine Canyons of New Guinea and South Australia[END_REF][START_REF] Hill | Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin[END_REF][START_REF] Hill | Ancestral Murray River on the Lacepede Shelf, southern Australia: Late Quaternary migrations of a major river outlet and strandline development[END_REF].

In terms of water masses, the Circumpolar Deep Water (CPDW) [START_REF] Emery | Global water masses: summary and review[END_REF] derived from the Antarctic Circumpolar Current and the Antarctic Bottom Waters (AABW) are the main deep water masses occurring from bottom to about ~1200 m water depth (Fig. 1c). From ~1200 m to 850 m, the Antarctic Intermediate Water (AAIW) is present and from ~850 to 450 m depth, the Sub-Antarctic Mode Water (SAMW) is dominant [START_REF] Passlow | Late Quaternary palaeoceanography near Tasmania, southern Australia. Palaeogeogr. Palaeoclimatol. Palaeoecol[END_REF] (Fig. 1c). Surface waters (250 -0 m) are mainly represented by the Subtropical Surface Water (STSW) [START_REF] Richardson | Shallow water masses and their connectivity along the southern Australian continental margin[END_REF] (Figure 1a; c). These surface waters are affected by the Leeuwin Current (LC), a winter stream of warm, relatively low-salinity, tropical, surface water. The LC hydrographic properties are well defined: Tropical Surface Water (TSW) from northwestern Australia and South Indian Central Water (SICW) from the West Australian Current mix and flow south and then east along the southern margin [START_REF] Cresswell | The Leeuwin Current south of Western Australia[END_REF][START_REF] Woo | Hydrography and water masses off the western Australian coast[END_REF][START_REF] Richardson | Shallow water masses and their connectivity along the southern Australian continental margin[END_REF] (Fig. 1a). Today and during the Holocene, the LC is/was most effective at reaching 135-140°E during the austral winter, during La Niña phases, that affect the region [START_REF] De Deckker | Influence of the tropics and southern westerlies on glacial interhemispheric asymmetry[END_REF][START_REF] Perner | Heat export from the tropics drives mid to late Holocene palaeoceanographic changes offshore southern Australia[END_REF]. During the last glacial period, the LC was overall absent or weaker in the study area [START_REF] De Deckker | Influence of the tropics and southern westerlies on glacial interhemispheric asymmetry[END_REF].

The Flinders Undercurrent also passes over the Murray Canyon Group and flows west along the continental slope of southern Australia (cf. [START_REF] Middleton | A review of the shelf-slope circulation along Australia's southern shelves: Cape Leeuwin to Portland[END_REF] for further details). The LC overrides the Flinders Undercurrent when present.

Material and methods

Radiocarbon dating was determined by accelerator mass spectrometry on mono-specific samples of the planktonic foraminiferal species Globorotalia inflata and Orbulina universa, except for one sediment sample (212 cm) for which we used a mixture of the two species (Table 1). A minimum of 7 mg per sample was extracted from the >150 μm size fraction in seven sediment samples (Table 1). Only the muddy intervals, theoretically representing the hemipelagic sedimentation, were selected for dating (Fig. 2).

Radiocarbon dating was performed by UMS-ARTEMIS (Pelletron 3MV) AMS facilities (CNRS-CEA Saclay, France), following the standard procedure described by [START_REF] Tisnérat-Laborde | Development of a semi-automated system for routine preparation of carbonate samples[END_REF]. For the three sediment levels where two 14 C dates were obtained (23-24 cm, 45-46 cm et 160-161 cm; Table 1), we calculated the average 14 C age and we combined the errors using propagation of uncertainty. Conversion into calendar years was obtained with Calib7.1.0 software and the "SHCal13" calibration curve [START_REF] Hogg | SHCal13 Southern Hemisphere Calibration, 0-50,000 Years cal BP[END_REF][START_REF] Reimer | IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP[END_REF] after applying a -367 ± 167 year reservoir correction (average value from four nearest locations from the global data base in http://www.calib.qub.ac.uk/marine).

Using visual observation and high-resolution photographs (Fig. 2), we performed a detailed and rigorous visual description of the studied core in terms of lithology, sedimentary structures, bioturbation features and colour (Fig. 2). All these observations were compiled in the form of a sedimentological log and a descriptive curve of the three main grain size fractions presented in Fig. 2.

The core was sub-sampled at different sediment layers and were each one cm thick, guided by the various sedimentological features (Fig. 2). The collected samples were washed over sieves of 150 μm openings, dried and split with an Otto microsplitter.

Whole splits were counted until a minimum of 200 tests of benthic foraminifera was obtained. Foraminifera were then picked under the binocular. The benthic foraminiferal faunas were analysed for different sediment layers following the various sedimentological features (Fig. 2). For each subsample, a known volume of sediment was processed for foraminiferal analysis, wet-weighed, dried and re-weighed to obtain dry weight. Benthic foraminiferal species ranging from estuarine, upper shelf to abyssal faunas were identified using reference taxonomic studies in the area [START_REF] Hayward | Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment[END_REF][START_REF] Hayward | Recent New Zealand deep-water benthic foraminifera: taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment, GNS Science monograph[END_REF][START_REF] Debenay | A guide to 1,000 foraminifera from southwestern Pacific: New Caledonia[END_REF]. In order to help with taxonomical identification, Scanning Electron Microscope (SEM) photographs were obtained at the Centre for Advanced Microscopy (Australian National University, Canberra) using the Zeiss UltraPlus analytical FESEM after Gold coating the specimens in an EMITECH EMITECH K550X coater (Plates 1 to 4).

Diversity (Shannon H) index and Principal Component Analysis (PCA) was calculated using the software PAST (PAleontological STatistics;Version 3.25;Hammer et al., 2001). Input for the PCA consisted of species' relative abundance data (correlation matrix). Only taxa occurring with ≥5% in at least one sample were retained in these statistical analyses.

Results

Lithology and grain size

Core SS02/06-GC2 is characterized by a succession of sediment layers of variable colours spanning from light to dark olive-grey sediments from 255 to 95 cm depth to light brownish grey sediments in the top 95 cm (using a Munsell colour chart codes in Fig. 2). Every colour change is accompanied in most cases by a change in particle size (Fig. 2).

The range of particle sizes is large, going from clays to silts to coarse sands, with the sandy and silty levels being usually rich in shell debris (Fig. 2). Several erosional contacts are also observed along the core. All these lithological features are indicative of a dynamic and likely discontinuous sedimentation due to high-energy reworking and transport processes, such as those characterizing submarine canyon turbidity deposits (e.g. [START_REF] Mulder | Present deep-submarine canyons activity in the Bay of Biscay (NE Atlantic)[END_REF][START_REF] Lombo Tombo | Sea-level control on turbidite activity in the Rhone canyon and the upper fan during the Last Glacial Maximum and Early deglacial[END_REF]. These turbidites are mostly characterized by a normal grading, going from coarse sand at the base into finer sand silt and clay upward, and often, an erosional base is present (Fig. 2). The unavailability of high resolution X-ray images prevent us from a more detailed description of the different lithofacies, and especially from identifying sedimentary structures such as linear/crossed laminations that could help us discriminating between the various turbidite sequences (e.g. [START_REF] Mulder | Marine hyperpycnal flows: initiation, behavior and related deposits. A review[END_REF][START_REF] Shanmugam | The hyperpycnite problem[END_REF].

Because of the presence of turbidite deposits, we decided not to build an age model for this study and only use the obtained 14 C dates to give a general chronological framework.

The results show that core SS02/06-GC2 covers a time-period from ~40 to 12 cal ka BP, with a discontinuous sedimentation. Caution is required regarding 14 C ages, as turbidites seem to have been deposited only at four specific time-periods: 1) At ~40-35 cal ka BP (between ~255 cm and 181 cm sediment depth), 2) at ~32 cal ka BP (from ~181 cm to 157 cm), 3) at ~21 cal ka BP, (from ~157 cm to 122 cm), and 4) at ~12.8 cal ka BP (the upper ~122 cm) (Figs. 2 and5). Since there are no 14 C ages above 23 cm sediment depth, perhaps a part of these sediments may have been deposited later during the Holocene.

Foraminiferal analyses

A total number of 294 benthic foraminiferal species were determined in core SS02/06-GC02, among which 33 are dominant and show relative abundances ≥5% in at least one sample. In order to facilitate examination of the large dataset obtained (Dataset S1) and to extract the main faunal ecological groups, a PCA was performed based on the percentage data of these dominant taxa (Fig. 3a). Axes 1 and 2 account respectively for 20.86% and 16.33% of the total variance of the dataset. The PCA separates the faunal assemblages into three main species groups with rather similar bathymetric/ecological characteristics (Fig. 3b):

Group 1 is composed of Rosalina bradyi/globularis, Miliolinella subrotundata, Sphaeroidina bulloides, Elphidium excavatum, Elphidium crispum, Gavelinopsis praegeri, Rosalina anomala, Nonion pacificum/Haynesina depressula, Spirillina sp., and Bolivina earlandi. Most of these species are outer estuarine/inner continental shelf species (e.g. [START_REF] Hayward | Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment[END_REF][START_REF] Hayward | Recent New Zealand deep-water benthic foraminifera: taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment, GNS Science monograph[END_REF][START_REF] Debenay | A guide to 1,000 foraminifera from southwestern Pacific: New Caledonia[END_REF][START_REF] Mojtahid | Spatial distribution of living (Rose Bengal stained) benthic foraminifera in the Loire estuary (western France)[END_REF] (Fig. 3b).

Nonion pacificum and H. depressula are lumped together because the taxonomic differentiation between these two morphologically similar species has been problematic.

Especially, we could not systematically observe the star-shaped umbilicus characteristic of H. depressula, probably because abrasion during transport from shallow depths towards the abyssal area may have altered the tests.

Group 2 is composed of Uvigerina mediterranea, Spiroplectinella proxispira, Cibicides refulgens, Cibicides variabilis, Cibicidoides pachyderma, Cibicidoides dispars s.l.,

Cibicides lobatulus, Globocassidulina subglobosa, Quinqueloculina auberiana, Trifarina angulosa, and Notorotalia clathrata. Most of these species have in common a bathyal depth habitat according to their modern distribution and most extend onto mid to outer shelf as well (e.g. [START_REF] Li | Mixed Foraminiferal Biofacies on the Mesotrophic, Mid-Latitude Lacepede Shelf, South Australia[END_REF][START_REF] Hayward | Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment[END_REF][START_REF] Hayward | Recent New Zealand deep-water benthic foraminifera: taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment, GNS Science monograph[END_REF][START_REF] Mojtahid | Live benthic foraminiferal faunas along a bathymetrical transect (140-4800 m) in the Bay of Biscay (NE Atlantic)[END_REF][START_REF] Debenay | A guide to 1,000 foraminifera from southwestern Pacific: New Caledonia[END_REF] (Fig. 3b).

Group 3 is composed of Epistominella exigua/vitrea, Cibicidoides wuellerstorfi, Melonis affinis/barleeanus, Nuttalides umbonifera, Pullenia bulloides, Oridorsalis umbonatus, Oridorsalis tenerus, Oolina spp., Gyroidina orbicularis, Fursenkoina complanata, Cibicidoides robertsonianus, and Uvigerina peregrina s.l. Although these species have a large bathymetric range, they all inhabit lower bathyal to abyssal depths (e.g. [START_REF] Hayward | Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment[END_REF][START_REF] Hayward | Recent New Zealand deep-water benthic foraminifera: taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment, GNS Science monograph[END_REF][START_REF] Mojtahid | Live benthic foraminiferal faunas along a bathymetrical transect (140-4800 m) in the Bay of Biscay (NE Atlantic)[END_REF][START_REF] Debenay | A guide to 1,000 foraminifera from southwestern Pacific: New Caledonia[END_REF] (Fig. 3b).

All groups are present throughout the record, but each of them dominates specific sediment intervals (Figs 4; 5d):

Group 1 (mostly shelf faunas) is dominant at 255-220 cm, 188-183 cm, 170-169 cm, 92-91 cm, 61-59 cm, 31-30 cm and 6-2 cm sediment depths (cf. light grey bands in Fig. 4).

Except for the sandy 255-220 cm sediment interval, this group dominates the silty levels that are characterized by intermediate total absolute densities of foraminiferal faunas (164±183 g/dry sediment) and the highest Shannon index (3.56±0.16) and total species number (69±16) (Fig. 4).

Group 2 (mostly bathyal faunas) is dominant at 199-190 cm, 178-179 cm*, 118-119 cm*, 125-99 cm, 95-94 cm*, 64-63 cm, and 34-33 cm sediment depths (cf. dark grey bands in Fig. 4). This group dominates the sandy and coarse sandy levels that are characterized by maximum total absolute densities of foraminiferal faunas (791±483 g/dry sediment) and intermediate Shannon index (3.45±0.16) and total species number (55±9) (Fig. 4). The samples indicated by an asterisk were investigated only qualitatively because of some sediment loss.

Group 3 (mostly abyssal faunas) is dominant at 213-204 cm, 184-183 cm, 161-130 cm, 86-68 cm, 56-38 cm, 24-14 cm, and 1-0 cm sediment depths (cf. white bands in Fig. 4).

This group dominates the clayey levels that are characterized by minimum total absolute densities of foraminiferal faunas (26±9 g/dry sediment) and minimum Shannon index (3.14±0.44) and total species number (47±16) (Fig. 4).

Discussion

Succession of sediment deposits in the abyssal plain of the Murray Canyon

Group

The studied abyssal site is characterized by obviously very dynamic and discontinuous sedimentation, indicated by clear changes in sediments colours, several erosional surfaces and a highly fluctuating grain size distribution spanning from coarse sands to clays (Fig. 5a-b). This is further corroborated by the 14 C dates showing short time periods of large sediment deposits (e.g. ~40-35 ka cal BP and ~12.8 ka cal BP), interrupted by periods of lower sedimentation rates and probably lack of sedimentation (Fig. 2). All these sedimentary features point to a succession of turbidite deposits (Fig. 5a-b), corroborating, therefore, the morphobathymetric map interpretation of the large deep-water holes in the abyssal area (Fig. 1b) being gouged by surges of turbidity currents [START_REF] Hill | AUSCAN seafloor mapping and geological sampling survey on the Australian southern margin by RV Marion Dufresne in 2003: Final project report[END_REF][START_REF] Hill | Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin[END_REF]. These turbidites are characterized by a normal grading (Fig. 5b), going from coarse sand at the base into finer sand silt and clay upward (e.g. [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF][START_REF] Middleton | Sediment gravity flows: mechanics of flow and deposition[END_REF][START_REF] Walker | Facies Models 2. Turbidites and Associated Coarse Clastic Deposits[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] Shanmugam | The Bouma Sequence and the turbidite mind set[END_REF] (Fig. 5e). Regarding these sedimentological characteristics, the turbidite sequence deposits can be described as distal (i.e. absence of pebbles ; [START_REF] Walker | Facies Models 2. Turbidites and Associated Coarse Clastic Deposits[END_REF], "classical" Bouma-like sequences (Figure 5e). In core SS02/06-GC2, we do not always observe an entire Bouma sequence; sometimes it seems to be truncated either of its higher layers (e.g. 120-115 cm sediment depth) or of its lower layers (e.g. 150-125 cm sediment depth) (Fig. 5b). For simplicity, we defined seven Bouma-like sequences (Bs1 to Bs7), without considering the "small" turbidity events, or the truncated sequences (Fig. 5b). [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF] associated the vertical evolution of the terms, from "Ta" to "Te" (Fig. 5e), with over time the evolution of the transport capacity and the speed of the turbidity current. Indeed, the energy (bed shear stress) is decreasing upwards as the current passes by, and this is also manifested in the normal grading of the bed -coarser at the base, finer at the top (e.g. [START_REF] Zavala | Table caption Table 1. Radiocarbon dates, calibrated ages (cal. year BP; 2 sigma) and their corresponding sediment depths and dated material listing species[END_REF]. Although evidence of reworking and transport is present in all samples, it is in the silty and sandy layers of the turbidites that this is most obvious with the high abundance of shallow (e.g. Rosalina spp., Elphidium spp.)

and bathyal benthic species (e.g. U. mediterranea, C. refulgens) (Figs. 4 and5d). This feature is common in other turbidity systems (e.g. [START_REF] Zaragosi | The impact of the last European deglaciation on the deep-sea turbidite systems of the Celtic-Armorican margin (Bay of Biscay)[END_REF][START_REF] Lombo Tombo | Sea-level control on turbidite activity in the Rhone canyon and the upper fan during the Last Glacial Maximum and Early deglacial[END_REF]. Because it contains few shallow and bathyal benthic foraminifera, some of the clay might have been introduced into the area by the turbidity current and/or by river-generated plumes, but since it contains mostly abyssal benthic species (e.g.

Epistominella spp., C. wuellerstorfi), the clay layer more likely represents the constant slow rain of mud onto the ocean floor (Figs. 4 and5d).

Source of the abyssal turbidite deposits inferred from benthic foraminiferal communities

According to [START_REF] Middleton | Sediment gravity flows: mechanics of flow and deposition[END_REF], classical turbidity sequences such as the one we observed here, result from low-concentration turbidity currents that are either initiated by a river in flood or slump/slide processes from the upper slope. In core SS02/06-GC2, the presence of very shallow inner shelf species (e.g. Rosalina spp., E.

crispum) and some outer estuarine species (E. excavatum and most probably H. depressula) [START_REF] Hayward | Recent New Zealand deep-water benthic foraminifera: taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment, GNS Science monograph[END_REF][START_REF] Hayward | Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment[END_REF][START_REF] Debenay | A guide to 1,000 foraminifera from southwestern Pacific: New Caledonia[END_REF]) (PCA group 1; Fig. 3) mainly in the silty layers of the turbidite deposits (Figs. 4 and5), indicate an inner shelf-related source, most likely nearby the Murray mouth. Additionally, within PCA group 1, we observed that individuals are overall small-sized belonging mostly to flat-shaped foraminiferal species (e.g. Elphidium spp., Rosalina spp., G. praegeri), some of which are known for their epibenthic/epiphytic habitats (e.g. Rosalina spp.). All these criteria make these species particularly prone to transport, in suspension or attached to floating sea grass or algae (Jorissen and Whittling, 1999;[START_REF] Murray | Ecology and Applications of Benthic Foraminifera[END_REF], by currents and/or river plumes during periods of high river runoff (e.g. [START_REF] Duros | Live and dead benthic foraminiferal faunas from Whittard Canyon (NE Atlantic): Focus on taphonomic processes and paleo-environmental applications[END_REF][START_REF] Garcia | Benthic and Planktic Foraminifera as Indicators of Late Glacial to Holocene Paleoclimatic Changes in a Marginal Environment: An Example from the Southeastern Bay of Biscay[END_REF][START_REF] Mojtahid | High resolution Holocene record in the southeastern Bay of Biscay: Global versus regional climate signals[END_REF][START_REF] Durand | Late Holocene record from a Loire River incised paleovalley (French inner continental shelf): Insights into regional and global forcing factors[END_REF]. Therefore, our foraminiferal observations seem to argue in favour of a river in flood origin, at least for the silty layers. In that case, one of the most documented mechanisms of implementation could be the presence of hyperpycnal currents (e.g. [START_REF] Mulder | Des courants de turbidité hyperpycnaux dans la tête du canyon du Var ? Données hydrologiques et observations de terrain[END_REF]. Using experimental models and in-situ measurements, the particulate concentration threshold necessary to generate a hyperpycnal flow can be lowered from the initial value of 35-40 kg m -3 (e.g. [START_REF] Mulder | Des courants de turbidité hyperpycnaux dans la tête du canyon du Var ? Données hydrologiques et observations de terrain[END_REF] to 5 kg m -3 because of concentration phenomena increasing the flow density (such as by flocculation, convective instability and local hydrodynamic conditions) (e.g. [START_REF] Parsons | Hyperpycnal plume formation from riverine outflows with small sediment concentrations[END_REF][START_REF] Felix | Combined measurements of velocity and concentration in experimental turbidity currents[END_REF]. As a result, about 80% of rivers worldwide can engender hyperpycnal flows in the marine environment, with a frequency of less than one per century (e.g. [START_REF] Mulder | Turbidity Currents Generated at River Mouths during Exceptional Discharges to the World Oceans[END_REF][START_REF] Mulder | Marine hyperpycnal flows: initiation, behavior and related deposits. A review[END_REF][START_REF] Wright | Gravity-driven sediment transport on continental shelves: A status report[END_REF]. Accordingly, and despite its modern relatively low freshwater discharge (6 -160 m 3 s -1 ; [START_REF] Grafton | Water Planning and Hydro-Climatic Change in the Murray-Darling Basin, Australia[END_REF], the River Murray could potentially produce hyperpycnal flows, at least during periods of low sea-level in the past and/or periods of high river runoff.

Using the modern bathymetric range of each of the main benthic foraminiferal species present in our core [START_REF] Hayward | Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment[END_REF][START_REF] Hayward | Recent New Zealand deep-water benthic foraminifera: taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment, GNS Science monograph[END_REF][START_REF] Debenay | A guide to 1,000 foraminifera from southwestern Pacific: New Caledonia[END_REF] (Dataset S1), we can deduce the source origin of sediments reaching the abyssal area. In our samples, a quasisystematic succession in foraminiferal ecological PCA groups stands out for each of the defined Bouma-like sequences (Fig. 5d): nearly all sequences start with the dominance of bathyal species in the coarse-grained base, followed by the dominance of shallow species in the silty part, and finally with abyssal species in the clays (Fig. 5d). Apart from the clay layer that represents mostly the natural hemipelagic background in the abyssal area, the bathyal/shallow allochthonous species succession clearly indicates two different sources of transported sediments for each recorded turbidity event (i.e. one Bouma-like sequence). Because there is no reason why foraminiferal species from two different ecological groups follow the grain size downgrading within a turbidity current, our findings clearly question a process involving a single hyperpycnal flow as we previously hypothesized.

An alternative scenario is presented in the study of [START_REF] Mulder | Des courants de turbidité hyperpycnaux dans la tête du canyon du Var ? Données hydrologiques et observations de terrain[END_REF]. According to these authors, hypopycnal and mesopycnal plumes can be produced in addition to hyperpycnal flows and/or turbidity currents during river floods (Fig. 6). As such, we hypothesize the following scenario:

(1) the high sedimentation rate at the river mouth and into the adjacent ocean and increased particulate load during river flood events can create high instability of the upper slope at the "plunge point". This might trigger hyperpycnal flows or turbidity currents when high sediment load creates shallow failures of the upper slope sediments through excess pore pressure (see review in [START_REF] Shanmugam | The hyperpycnite problem[END_REF]. In both cases, coarse grained materials can be dragged at the base as bedload by shear forces, therefore transporting bathyal species down to the abyssal plain. This might explain their dominance in the sandy base of our Bouma-like sequences (Fig. 6b).

(2) meanwhile, hyperpycnal and mesopycnal plumes may have formed from the same river flood event, carrying silts and clays in suspension to the abyssal plain. Shallowwater benthic species with a large fraction of epiphytes/epibenthics (e.g. Rosalina spp., G. praegeri; Fig. 4) can be transported in suspension by the plumes and eventually be deposited at the study site by hemipelagic sedimentation. Because this mode of sedimentation is slower in time relatively to the bed load transport, the decaying silts with a high proportion of shallow-water species are deposited on top of the sandy base.

It its however difficult to separate the silty fraction originating from the turbulent flow, as strictly defined for the Bouma sequence, from that cascading from the hypopycnal and mesopycnal plumes. This might explain the non-exclusive presence of either of the two ecological groups in the sandy and silty layers of the turbidity deposit despite their respective dominance (Fig. 6b).

(3) the drastic decrease in foraminiferal absolute densities and the dominance of abyssal benthic species (e.g. Epistominella spp., C. wuellerstorfi) in the clayey layers of the Bouma-like sequences indicate a decline and/or cessation of the turbidity current. As such, the clay deposit more likely represents the constant, slow 'rain' of mud over the ocean floor to which the abyssal oligotrophic species are usually adapted (Figs. 4 and5d). Still, the presence of few shallow and bathyal benthic species in these muddy layers might indicate that some of the clays have been transported in suspension after storms for instance, by resuspension from the hypopycnal flow, and/or by a low-density current as defined by [START_REF] Middleton | Sediment gravity flows: mechanics of flow and deposition[END_REF] (Fig. 5e).

Linking abyssal turbidite deposits to the climate of south Australia

Based on the 14 C dated clayey layers, core SS2/06-GC2 covers a time-period spanning from approximately 40 to 12 cal ka BP (Fig. 2). This encompasses part of the last glacial period and the last deglaciation. At 40 cal ka BP, the relative sea-level (RSL) was lower than today by ~-60 m and continued its falling until reaching ~-130 m at the last glacial maximum (LGM) around 21 cal ka BP, followed by a rapid rise to reach ~-60 m at ~12 cal ka BP [START_REF] Waelbroeck | Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records[END_REF][START_REF] Lambeck | Sea level and global ice volumes from the Last Glacial Maximum to the Holocene[END_REF]. Although it is widely accepted that eustatic sea-level is a key factor controlling turbidite activity in most submarine canyon systems by altering the location of sediment deposition relative to the shelf edge (e.g. [START_REF] Lebreiro | Sediment instability on the Portuguese continental margin under abrupt glacial climate changes (last 60kyr)[END_REF][START_REF] Henrich | Climate and sea level induced turbidite activity in a canyon system offshore the hyperarid Western Sahara (Mauritania): The Timiris Canyon[END_REF][START_REF] Pierau | Late Quaternary climatic events and sea-level changes recorded by turbidite activity, Dakar Canyon, NW Africa[END_REF][START_REF] Lombo Tombo | Sea-level control on turbidite activity in the Rhone canyon and the upper fan during the Last Glacial Maximum and Early deglacial[END_REF], it is insufficient to explain alone the timing and intensity of turbidite deposits at our core location. Indeed, the largest turbidite deposits in core SS2/06-GC2

did not take place at the LGM when the maximum of the RSL fall was reached, but occurred around ~40-35 cal ka BP (Bs1 and Bs2), ~32 cal ka BP (the early part of Bs3), and ~12.8 cal ka BP (Bs4, Bs5, Bs6) (Figure 6b). Furthermore, at ~12.8 cal ka BP and ~40 cal ka BP, sea-level was lower than today by ~ -60 m [START_REF] Lambeck | Sea level and global ice volumes from the Last Glacial Maximum to the Holocene[END_REF], and therefore the palaeoshoreline was about halfway from its modern position (e.g. [START_REF] Gingele | Late Pleistocene and Holocene climate of SE Australia reconstructed from dust and river loads deposited offshore the River Murray Mouth[END_REF], meaning that the River Murray mouth was most likely disconnected from the canyon head most of the record. Furthermore, the similar foraminiferal successions in the pre-Holocene turbidite sequences compared the older turbidite deposits (Fig. 5b), strongly points to a common main triggering process, being rather independent from the RSL. As hypothesized in our model (Fig. 6), our turbidite deposits are most likely initiated by enhanced fluvial discharges.

A strong link exists between the intensity of fluvial sediment discharge to the Murray Canyon Group and climate of SE Australia (e.g. [START_REF] Gingele | Late Quaternary terrigenous sediments from the Murray Canyons area, offshore South Australia and their implications for sea level change, palaeoclimate and palaeodrainage of the Murray-Darling Basin[END_REF][START_REF] Gingele | Late Pleistocene and Holocene climate of SE Australia reconstructed from dust and river loads deposited offshore the River Murray Mouth[END_REF]Page et al., 2009;[START_REF] Petherick | Climatic records over the past 30 ka from temperate Australia -a synthesis from the Oz-INTIMATE workgroup[END_REF][START_REF] Bayon | Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings[END_REF]. Considering the limitations of 14 C dating in such dynamic sedimentary setting, the timing of large turbidite deposits in our study site seems to be remarkably consistent with palaeoclimatic evidence of overall humid climate on the continent:

The pre-LGM: On land, studies report significant fluvial activity in the Murray

Darling basin (e.g. ~30-18 ka; [START_REF] Petherick | Climatic records over the past 30 ka from temperate Australia -a synthesis from the Oz-INTIMATE workgroup[END_REF] together with higher lake levels (e.g. ~55-25 ka;Page et al., 2009). The more recent study of [START_REF] Bayon | Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings[END_REF] using neodymium isotopes from a marine sediment core, close to our study site, further states a strong link between episodes of massive iceberg discharges in the Northern Hemisphere (NH) (i.e. Heinrich stadials -HS) during the last glacial period and the intensity of River Murray discharges into the ocean. Such link is explained by the fact that these NH cooling events were accompanied by pronounced southward migrations of the Intertropical Convergence Zone (ITCZ) leading to increased monsoon rainfall as far south as about 32°S (e.g. [START_REF] Wang | Isotopic signals in two morphotypes of Globigerinoides ruber (white) from the South China Sea: implications for monsoon climate change during the last glacial cycle[END_REF][START_REF] Kanner | High-Latitude Forcing of the South American Summer Monsoon During the Last Glacial[END_REF][START_REF] Bayon | Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings[END_REF]. In our core, and albeit the uncertainties of 14 C dating, it is interesting to note that the oldest turbidite deposits around 40-35 cal ka BP (Bs1 and Bs2), and ~32 cal ka BP (the first part of Bs3) seem to coincide with Heinrich stadial 4 (HS4 ~40-38 cal ka BP; [START_REF] Wendt | Three-phased Heinrich Stadial 4 recorded in NE Brazil stalagmites[END_REF] and Heinrich stadial 3 (HS3 ~32-29 cal ka BP; [START_REF] Turney | Highprecision dating and correlation of ice, marine and terrestrial sequences spanning Heinrich Event 3: Testing mechanisms of interhemispheric change using New Zealand ancient kauri (Agathis australis)[END_REF] respectively, which seems therefore coherent with the conclusions of [START_REF] Bayon | Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings[END_REF].

The LGM: the predominant opinion in the literature is that conditions during the

LGM in SE Australia (21 ± 3 cal ka BP, [START_REF] Reeves | Climate variability over the last 35,000 years recorded in marine and terrestrial archives in the Australian region: an OZ-INTIMATE compilation[END_REF] were cold and arid (e.g. [START_REF] Williams | River response to Quaternary climatic fluctuations: evidence from the Son and Belan valleys, northcentral India[END_REF]Page et al., 2009), although some of the fluvial and lake records from the Murray Darling Basin (e.g. [START_REF] Mueller | Revisiting an arid LGM using fluvial archives: a luminescence chronology for palaeochannels of the Murrumbidgee River, south-eastern Australia[END_REF] The pre-Holocene: Higher proportions of fluvial illite in Murray Canyon sediments between 13.5 and 11.5 ka is coherent with a general increase in Murray River discharge and more humid conditions in the catchment area [START_REF] Gingele | Late Quaternary terrigenous sediments from the Murray Canyons area, offshore South Australia and their implications for sea level change, palaeoclimate and palaeodrainage of the Murray-Darling Basin[END_REF][START_REF] Gingele | Late Pleistocene and Holocene climate of SE Australia reconstructed from dust and river loads deposited offshore the River Murray Mouth[END_REF]. [START_REF] Nash | Micropalaeontological evidence for deglacial marine flooding of the ancient courses of the River Murray across the Lacepede Shelf, southern Australia[END_REF] who studied sediment cores from the River Murray paleochannels on the Lacepede shelf show a very high sediment accumulation within these ancient channels under estuarine conditions, coinciding with the drainage of meltwater pulses at the end of the last deglaciation. If it is not a matter of preservation, the concomitance between the drainage of meltwaters and wetter conditions on the continent could explain the larger number of turbidite deposits at ~12.8 cal ka BP compared to older ages. Also, we can't discard the role of strong continental shelf currents and waves in transporting sediments to the upper slope as it is the case today [START_REF] Li | Multigrain seabed sediment transport modelling for the south-west Australian Shelf[END_REF]. It very likely that shelf currents and waves might have started moving sediments from the recently submerged mid-inner shelf along and out to the canyon head and helped accentuating the upper slope instability at the plunge point that we hypothesized in our model (Fig. 6).

Similar processes have been hypothesized to explain the large turbidite deposits during the early Holocene in the Eel fan (offshore northern California) in connection to Eel River flooding events [START_REF] Paull | Sub-decadal turbidite frequency during the early Holocene: Eel Fan, offshore northern California[END_REF]. Because the Leeuwin Current is a very shallow current (flowing in the upper ~80 m of the water column when strong and the upper ~50 m when weak; [START_REF] Perner | Heat export from the tropics drives mid to late Holocene palaeoceanographic changes offshore southern Australia[END_REF] and because it was overall absent or weak in the study area during the last glacial period and most of the deglaciation [START_REF] De Deckker | Influence of the tropics and southern westerlies on glacial interhemispheric asymmetry[END_REF], we can't assume with high confidence that this current itself was capable of transporting sediments from the shelf to the canyon head at the end of the last deglaciation.

Conclusions

The sedimentary and foraminiferal characteristics of core SS0/06-GC02 indicate a succession of turbidites, deposited between ~40 and 12 cal ka BP. We described each of the turbidite deposits as distal, "classical" Bouma-like sequences. Unsurprisingly, it is in the sandy and silty layers of the turbidites that evidence of reworking and transport is most found with the dominance of shallow (e.g. Rosalina spp.) and bathyal benthic foraminiferal species (e.g. U. mediterranea). The presence of outer estuarine/upper inner shelf species (e.g. Rosalina spp., Elphidium excavatum) argues in favour of a river in flood origin causing the involved transport processes.

Using the modern bathymetric range of each of the main benthic species present in the core, we determined the source origin of sediments arriving to the abyssal area. We find a quasi-systematic succession in the three ecological PCA groups for each of the defined Bouma-like sequences: nearly all sequences start with the dominance of bathyal species in the coarse-grained base, followed by the dominance of shallow species in the silty portion, and finally with abyssal species in the clays. Our findings clearly question a process involving a single hyperpycnal flow. We hypothesize a mixed process involving: i) hypopycnal and mesopycnal plumes transporting shallow water benthic species with a large fraction of flat-shaped epibenthic species in suspension, and ii) hyperpycnal flow and/or turbidity current when the upper slope is destabilized under fluvial sediment load, dragging coarse grained material at the base transporting bathyal species to the abyssal plain.

The largest turbidite deposits in core SS2/06-GC2 did not take place during the LGM when the maximum of the RSL fall was reached, but occurred around 40-35 cal ka BP, 32 cal ka BP, and 12.8 cal ka BP. We hypothesize a strong link between the intensity of fluvial sediment discharge to the Murray Canyon Group and climate of SE Australia, but the core chronological control prevents us from being more certain of this hypothesis. e) The typical Bouma sequence showing the Ta to Te divisions [START_REF] Bouma | Sedimentology of some Flysch deposits: a graphic approach to facies interpretation[END_REF], reinterpreted by other authors [START_REF] Middleton | Sediment gravity flows: mechanics of flow and deposition[END_REF][START_REF] Lowe | Sediment gravity flows; II, Depositional models with special reference to the deposits of high-density turbidity currents[END_REF]Shanmugan, 1997).

  indicate the opposite. In the ocean, Gingele and De Deckker (2005) report an increase in dust input from the central desert areas to the Murray canyons, which they interpreted as increased aridity in the Murray-Darling Basin. In our study core, the turbiditic activity seem to be low at ~21 cal ka BP, as indicated by what seems to be a truncated/incomplete sequences of Bouma (the upper part of Bs3; Figure 5b), although parts of turbidite deposits can be removed where strong bottom currents may have prevented deposition (e.g. Stow and Smillie, 2020). The larger presence of the oligotrophic species O. umbonatus and O. tenerus in the clayey layers during the LGM (~157 -122 cm; Fig. 4) compared to the other time-intervals might in fact argue in favour of low fluvial nutrient input. Therefore, and being cautious regarding the timing of our deposits, our finding seems to indicate decreased discharges of the River Murray during the LGM, in connection with overall dry climate on the continent.

Figures caption Figure 1 .

 caption1 Figures caption

Figure 2 .

 2 Figure 2. From left to right: Photography and interpretative lithological logs of core SS02/06-GC02 and a descriptive curve of the three main grain size fractions (clay, silt and sand) based on sedimentological visual observation. Position in the core of the calibrated 14 C dates are shown in red. The sediment colours (e.g. 10YR/6/2) were determined using a Munsell color chart[START_REF] Munsell | A Pigment Color System and Notation[END_REF]. The white dots indicate sample locations. The yellow dots indicate the samples with some sediment loss that could not be quantified for their foraminiferal content.

Figure 3 .

 3 Figure 3. a) PCA analyses based on the percentages of the main benthic foraminiferal species (i.e. present with ≥5% in at least one of the sediment samples); b) The modern bathymetric distribution of the main benthic foraminiferal species, mostly after Haywardet al. (1999, 2010).

Figure 4 .

 4 Figure 4. Representation of the downcore Shannon index of biodiversity, the total absolute densities of benthic foraminifera standardized to per gram of dry sediment and species composition (only the main species occurring with ≥5% in at least one sample)

Figure 5 .

 5 Figure 5. Interpretative summary of the main results: a) The lithological logs. The yellow dots indicate the samples with some sediment loss that could not be quantified for their foraminiferal content; b) Interpretation of the grain-size curve in terms of Bouma turbiditic sequences (Bs1 -Bs7). The climatic time periods referred to in the text are indicated. HE: Heinrich Event; LGM: Last Glacial Maximum; c) The downcore Shannon index and total absolute densities of benthic foraminifera standardized per gram of dry sediment; d) Pie charts representing the cumulative percentages of the three main PCA ecological groups, averaged for a number of sediment layers determined from Figure 4;

Figure 6 .

 6 Figure 6. Interpretative summary scheme of the hydro-sedimentary processes leading the deposition of the Bouma-like sequences in core SS2-CG2. Figure 6 is modified from Mulder et al. (1997).

  Pyrgo inornata; 9) Pyrgo denticulata; 10) Pyrgo depressa; 11) Pyrgo oblonga; 12-14) Nummulopyrgo globulus; 15) Pseudomassilina sp.1; 16) Quinqueloculina sp.; 17) Plate 2. SEM photographs of: 23) Laevidentalina inornata? ; 24) Lagena spicata; 25) Mychostomina lucida ; 26-27) Pileolina zealandica ; 28) Siphogenerina raphana; 29)

	Miliolinella fichteliana?; 18-19) Quinqueloculina auberiana; 20) Quinqueloculina
	cuvieriana; 21-22) Quinqueloculina seminula.
	Bolivina Plate 4. SEM photographs of: 69-71) Gyroidina orbicularis; 72-73) Hoeglundina
	Tables caption elegans; 74) Planulinoides biconcavus; 75) Rosalina globularis; 76-78) Astrononion
	novozealandicum; 79) Elphidium charlottense?; 80) Elphidium sp.; 81-83) Elphidium
	Plate 1. SEM photographs of: 1-2) Textularia pseudogramen; 3) Textularia stricta;4) crispum; 84-88) Notorotalia clathrata; 89-91) Nuttallides bradyi?; 92) Evolvocassidulina
	Spirotextularia fistulosa; 5) Textularia goesi; 6) Gaudryina convexa; 7) Eggerella sp.; 8) belfordi; 93-94) Hemirobulina angistoma; 95-96) Sigmoidella elegantissima

alata; 30) Bolivinita quadrilatera; 31) Bolivinellina pescicula; 32) Fursenkoina schreibersiana?; 33) Bulimina marginata f. aculeata; 34) Bulimina striata; 35) Uvigerina mediterranea; 36) Uvigerina peregrina s.l.; 37) Trifarina angulosa; 38) Trifarina reussi; 39-40) Pullenia quinqueloba; 41) Anomalinulla glabrata; 42) Nonion pacificum/Haynesina depressula ? Plate 3. SEM photographs of: 43-47) Cibicidoides dispars s.l. ; 48-52) Cibicidoides wuellerstorfi; 53-55) Cibicides corticatus ; 56) Cibicides refulgens ; 57) Cibicides sp. 1 ; 58) Cibicides sp. 2 ; 59-63) Cibicides variabilis ; 64-66) Cibicidoides pachyderma ; 67-68) Cibicides lobatulus.

Acknowledgements

We are grateful to The Australian National Marine Facility for granting time on the RV Southern Surveyor to collect the core and obtaining additional bathymetry data processed by P. J. Hill and Michele Spinoccia. Don Mackenzie of CSIRO facilitated the collection of the core and Geoscience Australia loaned the gravity corer. We are thankful to the French 14 C AMS facility ARTEMIS for chemical preparation and measurements of the 14 C samples. The data are available online as supplementary material and/or by contacting the first author (e-mail: meryem.mojtahid@univ-angers.fr). We are very grateful to Maria Pia Nardelli for scientific discussions, and to the two reviewers Bruce Hayward and Maria-Angela Bassetti for their thorough reviews that significantly helped improve the manuscript.


Arthur Piraux
email: arthur.piraux@univ-angers.fr

Docteur En Pharmacie

Anne Mosnier

Médecin Généraliste

Thierry Barthelmé

Sous-dochead Les enseignements d'une crise sanitaire inédite Covigie, une plateforme pour les soignants et les coordonnateurs d'équipes de soins

Keywords: Covid-19, Covigie, officine, outil digital, soin de premier recours

Dispositif mis en place face à la pandémie mondiale de Covid-19, Covigie est une plateforme numérique, accessible en ligne gratuitement. Elle s'adresse à tous les soignants et coordonnateurs d'équipes de soins de premiers recours. Elle leur permet de faire remonter, en temps réel, aux autorités sanitaires françaises, les initiatives, les observations, les questionnements et les problèmes rencontrés dans la lutte contre ce virus. L'équipe Covigie résume les informations issues des différentes contributions reçues, individuelles ou collectives, les adresse aux autorités sanitaires et les partage avec les soignants.

T1 Concepts de l'outil Covigie

TEG1 Le projet Covigie est né d'un constat simple : les professionnels de santé de premier recours sont en première ligne de la lutte contre la Covid-19, mais les autorités sanitaires ne disposent pas de relais d'informations structurées leur permettant d'avoir une vision agrégée et actualisée des retours d'expérience de ces soignants extrahospitaliers. Portée par des organisations de professionnels de santé, la plateforme Covigie a été conçue pour combler ce manque avec quatre principes : retour d'information, pluriprofessionnalité, simplicité et rapidité (figure1).

TEG1 Le rôle de Covigie est renforcé lorsque les soignants de premiers recours, toutes professions confondues, constituent des groupes ou communautés (forum, mailing, WhatsApp, etc.), pour échanger librement sur les difficultés rencontrées, les outils et les solutions mises en place, ainsi que les questions qui restent en suspens. Un membre de cette communauté est alors désigné rapporteur et a pour mission de transmettre les informations de son groupe directement à la plateforme en ligne sur le site www.covigie.org. Des contributions individuelles sont également possibles. Covigie a été conçu en collaboration avec OpusLine et Organize and Promote Epidemiological Network/Réseau d'observation des maladies et des épidémies (Open Rome). L'équipe de pilotage, principalement constituée de soignants de terrain, est appuyée par un comité scientifique et un comité d'éthique TEG1 Les informations collectées par Covigie sont analysées régulièrement pour mettre en lumière les problématiques rencontrées par les professionnels de santé sur le terrain (infirmiers, médecins et pharmaciens principalement), les initiatives ou réponses développées et les signaux qui, pris individuellement, peuvent être considérés comme faibles, mais qui, par regroupement avec d'autres équipes, font sens. L'utilisation de fonctionnalités de l'intelligence artificielle est en cours de mise en place pour faciliter l'analyse de ces contributions. Des résumés réguliers synthétisent les principaux enseignements remontés à la plateforme ; ils sont immédiatement partagés avec les professionnels et transmis aux autorités de tutelle (ministère des Solidarités et de la Santé, Direction générale de la santé, agences sanitaires, agences régionales de santé, conseil scientifique Covid-19, etc.) mais également aux différentes organisations professionnelles (ordres professionnels, unions régionales des professionnels de santé, collèges, académies, etc.). Une communication plus large, via des communiqués de presse et via les réseaux sociaux, s'est peu à peu développée.

TEG1 Covigie est donc un véritable relais de l'information, fonctionnant à la fois de manière ascendante et descendante. Il est important de souligner que les résumés ne sont que le reflet de témoignages issus du terrain et ne prévalent en rien sur les messages délivrés par les autorités de santé. Ils n'ont pas fait l'objet de validation préalable par des comités scientifiques.

T1 Retours de terrain TEG1 Le traitement de la Covid-19, affection respiratoire émergente, a eu un retentissement important sur la prise en charge des patients, atteints ou non, tant à l'hôpital qu'en ville. Il a fallu repenser toute l'organisation des soins sur le territoire français, l'adapter en un temps minime pour assurer au mieux les soins des concitoyens.

TEG1 Mi-juin, après deux mois de fonctionnement, Covigie avait reçu plus de 250 contributions, colligées dans 14 résumés et un bilan. Le contenu des contributions a évolué selon les temps de l'épidémie.

TEG1 Dans un premier temps, l'un des éléments qui a préoccupé les soignants, avant même leur propre sécurité et donc l'accès à des équipements de protection individuelle, a été la diminution du recours aux soins des patients atteints d'une pathologie aiguë, autre que la Covid-19, ou chronique. En effet, bon nombre de personnes refusaient de se rendre chez le médecin généraliste ou dans un service d'accueil des urgences, par crainte d'y être contaminés par la Covid-19. Les pharmaciens d'officine et les infirmiers libéraux étaient alors en première ligne pour témoigner de ce constat, y faire face, mais aussi et surtout faire preuve de pédagogie envers leurs patients pour les inciter à consulter un médecin sans plus attendre [1]. TEG1 L'un des enjeux majeurs de la gestion de cette pandémie a aussi été celui de l'accès aux matériels de protection pour les soignants et pour l'entourage des patients traités à domicile. Au-delà du manque considérable de matériel, Covigie a aussi fait remonter les obstacles et incohérences de leur accès et proposé des solutions pratiques sur le terrain.

TEG1 Les questionnements concernant les moyens et règles du diagnostic ont été nombreux, évoluant au fil de l'émergence et de la mise à disposition de nouveaux outils et des connaissances.

TEG1 Enfin, la problématique de l'accès rapide des soignants aux informations utiles et nécessaires a été soulevée à de nombreuses reprises. Les pharmaciens ont pu profiter d'un canal de communication simple et opérationnel : les alertes sanitaires communiquées via le dossier pharmaceutique (DP-Alertes). Par cet outil, pratiquement quotidiennement et pendant plusieurs semaines, la Direction générale de la santé a diffusé des messages de santé publique et expliqué les modalités d'application des différentes mesures. Cependant, les nombreuses informations sont parfois venues se contredire, en particulier celles concernant la distribution des masques, qui a fait couler beaucoup d'encre. Au-delà des renseignements fournis par les autorités françaises, les professionnels de santé étaient en quête de données validées scientifiquement, utiles pour leur pratique et sur lesquelles ils pouvaient s'appuyer sans crainte. Cette situation inédite a demandé des réévaluations quotidiennes, compliquant les réponses à apporter à l'angoisse grandissante de la population. Les multiples initiatives qui ont tenté de collecter, trier, résumer, puis mettre en ligne et en libre accès les nombreuses informations n'ont pas toujours permis d'en simplifier l'accès.

TEG1 Certains médicaments ont joué un rôle important dans cette crise. En dehors des principaux produits utilisés dans le cadre de recherches cliniques au sein des hôpitaux, des soignants ont évoqué précocement (dès le premier résumé [2]) les possibles bienfaits de la vitamine D3, des inhibiteurs calciques ou des sartans. Par ailleurs, les pharmacies d'officine ont dû faire face à un afflux important de patients désireux d'obtenir du paracétamol dans les dernières heures précédant le confinement. Voilà la raison pour laquelle un arrêté en date du 23 mars a limité à deux le nombre de boîtes de paracétamol délivrables à un patient sans ordonnance en cas de symptômes (une seule boîte si asymptomatique). Quelques jours plus tard, nous apprenions que la prise d'anti-inflammatoires non stéroïdiens serait un facteur de gravité de l'affection au coronavirus. Là encore, les équipes officinales ont été en première ligne pour expliquer, rassurer et parfois contre-indiquer l'utilisation de ces molécules, disponibles en libre accès pour certaines.

T1 Initiatives mises en place

TEG1 Covigie a aussi été le témoin d'initiatives imaginées, construites et portées par les soignants eux-mêmes pour mieux faire face à l'épidémie. Beaucoup d'équipes pluriprofessionnelles de soins primaires se sont montées de manière informelle et ont appris à communiquer entre elles. L'outil WhatsApp semble avoir été utilisé pour mieux communiquer dans nombre des cas. Au-delà d'un partage d'informations relatives à la Covid-19, ces groupes de discussion ont permis d'apporter du réconfort et un soutien indispensable durant ces temps de crise sanitaire. Dans certains cas, ils ont permis la réquisition et la répartition de moyens de protection (masques et blouses principalement) qui venaient à manquer dans les débuts de la crise. Après plusieurs semaines d'utilisation accrue, et à la suite du déconfinement, ces groupes semblent être de moins en moins utilisés.

TEG1 La prévention était souvent au coeur des échanges (importance du confinement, du lavage des mains, du port du masque, et plus largement des mesures barrières en plus de la distanciation physique). Des demandes répétées ont été émises auprès des autorités de santé pour une communication, la plus large possible, sur le respect des différentes mesures barrières et sur le port du masque de manière adéquate (de sa mise en place jusqu'à son retrait et son élimination). Avant même leur recommandation généralisée, les soignants ont alerté sur les conseils à apporter pour l'entretien des masques dits grand public. Les affirmations sur l'intérêt ou le danger du port des gants ont été récurrentes et non consensuelles.

TEG1 D'autres propositions, parfois anecdotiques mais toujours à visée pratique, ont été faites dans des domaines variés comme l'utilisation du lecteur SESAM-Vitale pour lequel, afin de limiter les contacts, il a été conseillé une introduction de la carte Vitale par le patient lui-même et l'utilisation de rallonges de câbles Universal Serial Bus (USB) pour arriver à ce résultat.

T1 Signaux faibles observés

TEG1 Dès le lancement de la plateforme Covigie, les soignants ont souhaité partager et échanger sur les formes cliniques rencontrées, aussi diverses que variées. Les tableaux dits typiques, tels que la toux sèche ou la fièvre et les complications respiratoires nécessitant une hospitalisation, ont été rapidement complétés par la notion de troubles digestifs à type d'épisodes diarrhéiques (notamment chez le patient âgé), mais également de perte de goût et d'odorat [3].

TEG1 Les soignants ont également dû faire face et ont partagé via Covigie des symptômes moins évocateurs, du moins dans les premiers temps, tels que :

• des formes dermatologiques à type d'engelure [4] ;

• des atteintes nerveuses à type de névralgie ;

• la présence d'une urticaire fébrile pendant une période de quinze jours ;

• une fatigue extrême, persistant plusieurs semaines après l'infection initiale.

Mais la problématique des formes prolongées, voire évocatrices de rechute, a surtout généré de nombreuses remontées [5]. À la demande de virologues hospitaliers, les contributeurs Covigie ont été incités à décrire ces tableaux et à les explorer par sérologie et réaction en chaîne par polymérase. Une note de synthèse a été partagée. TEG1 Enfin, plusieurs cas de thrombose veineuse à type d'embolie pulmonaire ou de phlébite, survenues à distance l'infection (six à huit semaines après J0) ont été rapportés.

TEG1

T1 Conclusion

Mise en place très rapidement, au coeur de la crise sanitaire de la Covid-19, la plateforme Covigie souhaite être l'outil de tous les professionnels de santé du premier recours, pour une remontée rapide d'informations pertinentes depuis le terrain jusqu'aux autorités de tutelle, en charge de la décision.

Alors que l'épidémie semble marquer le pas, un premier bilan montre que Covigie a permis de mettre en lumière certains problèmes liés à la Covid-19 rencontrés, reconnus (difficultés diagnostiques, difficulté d'accès à des équipements de protection) ou non (arbres décisionnels pour des prises en charges particulières). Des propositions ont été faites, notamment pour une communication grand public sur la mise en oeuvre des gestes barrières. Enfin, des hypothèses ont émané de l'observation de signaux faibles, permettant de sensibiliser les autorités sanitaires pour une investigation plus poussée de ces signaux.

Au-delà des réseaux locaux déjà constitués, Covigie permet aussi de communiquer de manière pluriprofessionnelle et à l'échelon national.

Covigie a aujourd'hui vocation à évoluer après la crise sanitaire. L'objectif est de pérenniser l'outil, d'augmenter sa notoriété et son utilisation, tant par les soignants que par les autorités et de contribuer plus largement à l'amélioration du système de santé. Des pistes sont déjà en cours d'exploration, comme l'extension au champ de la qualité et de l'organisation des soins, un outil de mise en commun et de signalement orienté sur les communautés professionnelles territoriales de santé, un outil d'enquête à l'initiative des promoteurs, des partenaires ou des autorités…

  Parmi les autres signaux faibles transmis, plusieurs praticiens ont soulevé l'hypothèse d'un effet protecteur de la prise d'antihistaminiques avec notamment une réduction des symptômes postinfection. Un médecin exerçant dans le Grand Est a, par exemple, décrit une absence de cas de Covid-19 chez 89 de ses patients qui prenaient cette thérapeutique au long cours. TEG1 De même, certains établissements d'hébergement de personnes âgées dépendantes ont témoigné d'une moindre atteinte des patients souffrant de la maladie d'Alzheimer, sans pour autant pouvoir définir le facteur en question (séparation du patient des espaces de vie, effet intimement lié à la maladie elle-même ?).

Points à retenir

• Covigie est une plateforme en ligne, aujourd'hui centrée sur la Covid-19 et destinée à tous les soignants de première ligne.

• Ce dispositif veut être un outil simple d'accès pour tous les professionnels de santé et porté par eux.

• Covigie est un outil de remontée d'informations (problèmes, solutions et signaux faibles) entre soignants et vers les autorités sanitaires.

• Les contributions sont compilées par la plateforme, analysées par une équipe dédiée, parfois à l'aide de l'intelligence artificielle, puis adressées aux autorités sanitaires et partagées entre soignants.

• Pendant la crise, la prévention a été au coeur des échanges.

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Références

[1] Ministère des Solidarités et de la Santé. Prise en charge hors Covid-19. https://solidaritessante.gouv.fr/IMG/pdf/soins-hors-covid-19.pdf.

[2] Covigie. Signalons les problèmes, partageons les solutions. https://covigie.org/bilan/1.

[3] Haut Conseil de la santé publique. Signes cliniques d'orientation diagnostique du Covid-19. 1 er mai 2020. www.hcsp.fr/Explore.cgi/AvisRapportsDomaine?clefr=812.

[4] Blond B. Ce que l'on sait des signes dermatologiques liés au Covid. 5 juin 2020. www.egora.fr/actusmedicales/dermatologie-infectiologie/59541-ce-que-l-on-sait-des-signes-dermatologiques-lies-au#xtor=EPR-3-5%5BNews_Best_Of_Médecine%5D-20200607-%5B_1%5D.

[5] Académie nationale de médecine. Communiqué de l'Académie :Suivi des patients convalescents de la Covid-19 par le médecin généraliste. 2 juin 2020. www.academie-medecine.fr/suivi-des-patients-convalescents-de-la-covid-19-parle-medecin-generaliste/.

Figure

© Open Rome

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Florence Brugnon
email: fbrugnon@chu-clermontferrand.fr

Dochead Dossier Sous-dochead La périnatalité à l'épreuve du Covid-19 Gestion des activités d'AMP dans un contexte pandémique

La crise sanitaire et les mesures mises en place pour éviter la propagation du Covid-19 en mars 2020 ont conduit à l'interruption des activités d'assistance médicale à la procréation (AMP). Cette situation a fortement fragilisé les couples dans leur parcours d'AMP. Dans le cadre d'une réflexion sur la reprise de ces activités, l'Agence de la biomédecine a émis, dès le mois de mai, des recommandations sur les modalités de prise en charge des couples en contexte de circulation du Sars-CoV-2.

L'Agence de la biomédecine, établissement public dépendant du ministère en charge de la Santé créé par la loi de bioéthique de 2004 [1], exerce ses missions dans quatre grands domaines de la biologie et de la médecine humaines : l'assistance médicale à la procréation (AMP) ; le diagnostic prénatal et génétique ; la recherche sur l'embryon et les cellules souches embryonnaires ; le prélèvement et la greffe d'organes, de tissus et de cellules. En mars 2020, le gouvernement français a instauré le confinement de la population pour freiner la propagation du coronavirus Severe Acute Respiratory Syndrome Coronavirus 2 (Sars-Cov-2. Les établissements de santé ont été sommés d'établir de nouvelles règles d'organisation répondant aux normes de l'urgence sanitaire. Les activités d'AMP ont dû, à l'instar de nombreuses autres, être interrompues car, malgré toutes les précautions prises à l'ordinaire dans ce secteur, il n'était pas envisageable, pour la bonne marche des services de l'hôpital et la sécurité de tous, de les poursuivre. Les couples ont été avertis soit par messagerie électronique, soit par téléphone de l'arrêt des activités d'AMP recommandé par l'Agence de la biomédecine [START_REF]Recommandations mises à jour concernant les activités d'assistance médicale à la procréation durant l'épidémie de SARS-CoV-2. 25 mars 2020[END_REF]. Cette décision a soulevé de nombreuses inquiétudes chez ces patients dont le parcours a été interrompu et qui ont vu leurs chances de procréer réduites à titre temporaire par ce nouveau délai d'attente. Un soutien a été maintenu pour expliquer la situation et rassurer.

T1 Décision de reprise des activités d'AMP TEG1 L'ensemble des services d'AMP de

France ont reçu un communiqué mi-mai 2020 les incitant à organiser, dans la mesure du possible, la reprise des activités dans les différents centres publics et privés autorisés sur le territoire. Ce texte précisait les mesures requises et leur aménagement en fonction des paramètres sanitaires. TEG1 L'Agence de la biomédecine avait, en effet, mis en place un groupe de travail 1 afin de préparer cette reprise à compter du 11 mai 2020, date officielle de déconfinement. Pour encadrer ce redémarrage en adaptant les modalités de prise en charge et de suivi au contexte de circulation virale et d'incertitudes liées au devenir de la pandémie, de nouvelles recommandations issues de ce travail de concertation ont été élaborées [START_REF]Recommandations sur les modalités de reprise des activités d'assistance médicale à la procréation en contexte de circulation du SARS[END_REF]. L'Agence a précisé à cette occasion que si ces

préconisations « constituent un préalable à la reprise des activités dans les centres d'AMP, les ARS [étaient] chargées d'autoriser ou non la reprise des activités médicales dans les établissements de santé, selon les conditions locales et régionales de circulation du virus ».

T1 Sécurité avant tout TEG1 La prise en charge des patient(e)s devant répondre aux exigences de respect des préconisations sanitaires en vigueur (gestes barrières et distances sociales), l'Agence de la biomédecine avait préconisé « une reprise des activités d'AMP progressive, évolutive et répondant à des critères de sécurité sanitaire stricts afin de limiter les risques de contamination, tant pour les patient(e)s que pour le personnel de santé ». TEG1 Parce qu'il était nécessaire de hiérarchiser les prises en charge, une liste a été établie pour aider les centres d'AMP à prioriser un dossier par rapport à un autre. Les équipes médicales ont donc été appelées à évaluer chaque cas en se référant aux situations prioritaires déterminées par le groupe de travail : • une indication de préservation de la fertilité urgente (patients sous traitement anticancéreux susceptible d'impacter la fertilité notamment) ; • un âge avancé ou une diminution de la réserve ovarienne affectant les chances de procréation ; • une tentative de stimulation annulée en mars 2020 à la suite de l'arrêt des activités d'AMP. TEG1 Par ailleurs, l'Agence a recommandé aux centres d'AMP de reporter, jusqu'à nouvel ordre et sauf cas particulier, la prise en charge des patient(e)s à risque de complications sévères en cas de contamination par le Covid-19 (antécédents de pathologie chronique respiratoire, accident vasculaire cérébral, diabète, surpoids, etc.). TEG1 Ce travail préalable d'évaluation et de vérification a pris du temps, ce qui n'a pas permis d'arrêter les rendez-vous et les programmations très rapidement. En outre, les couples n'habitant bien souvent pas le département où est situé le centre d'AMP, l'organisation s'est avérée compliquée, d'autant plus qu'il était difficile de différer des dates dans ce processus particulier. L'Agence de la biomédecine avait donc conseillé aux patient(e)s de rester en contact avec l'équipe du centre d'AMP qui les suivait, équipe qui était tenue de les informer des dispositions et évolutions éventuelles mises en oeuvre concernant leur parcours.

T1 Risques d'une nouvelle interruption d'activités

TEG1 Le virus circulant toujours parmi la population, l'Agence de la biomédecine avait souhaité également envisager les situations susceptibles de conduire à interrompre à nouveau les activités d'un centre d'AMP, qu'elles soient liées au couple lui-même, à l'établissement ou à une évolution des connaissances scientifiques : • suspicion d'une infection par le Covid-19 chez un des membres du couple ou dans son entourage ; • arrivée d'une nouvelle vague de la pandémie, avec un trop grand nombre de personnels du centre d'AMP affecté à la prise en charge des patients atteints dans d'autres unités ou trop de salariés du centre touchés ; • l'identification d'un risque en lien avec le Covid-19 pour la santé de la femme, de l'homme ou du foetus, par exemple. TEG1 Elle précisait également que si le centre le plus proche ou celui qui suivait les patient(e)s avant la pandémie n'était pas ou plus en capacité d'accueillir les couples nécessitant une prise en charge considérée comme urgente, ces derniers pouvaient s'adresser à une autre structure, si possible dans le cadre d'une convention de coopération. Les centres étaient bien sûr appelés à répondre aux inquiétudes des patients et à assurer une prise en charge de qualité.

T1 Conclusion

Les recommandations concernant les modalités de reprise des activités d'AMP en contexte de circulation du Sars-CoV-2 ont été communiquées, en mai dernier, aux sites et aux interlocuteurs concernés. Il était entendu que ces premières mesures feraient l'objet d'aménagements au fur et à mesure de l'évolution de la situation sanitaire liée au Covid-19 et des connaissances médicales.

En concertation avec ses équipes médicales, chaque centre a veillé à appliquer ces consignes. Les prises en charge en AMP font donc l'objet de précautions importantes, ce qui était toutefois déjà le cas avant que cette situation particulière s'impose. Les sages-femmes rencontrant les couples concernés devaient être en mesure de répondre à leurs interrogations, souvent nombreuses. Il faut espérer que la situation continue à évoluer plutôt favorablement afin de renouer avec l'espoir de pouvoir continuer à offrir aux couples en attente la possibilité de bénéficier de cette prise en charge.

Encadré flottant

Un parcours d'AMP mis à mal J. et V. avaient déjà commencé un parcours d'assistance médicale à la procréation (AMP) quand l'épidémie de Covid-19 a déferlé sur la France. En juin dernier, et alors qu'ils restaient dans l'attente de nouvelles concrètes, ils ont accepté de livrer leur témoignage.

T1 Annonce

Le service d'AMP nous a informés, par mail, le 13 mars 2020, de l'arrêt de la prise en charge : J. devait stopper le protocole qu'elle avait commencé. Nous étions approximativement à un mois de notre première fécondation in vitro par injection intracytoplasmique après plus de trois ans d'essai sans assistance. Si près du but, cette annonce a représenté un moment particulièrement difficile à vivre, même si nous pressentions que cela allait se produire.

T1 Acceptation

Nous avions évoqué cette éventualité avant de recevoir le message et avions décidé d'anticiper en appelant le secrétariat du centre d'AMP, qui nous avait expliqué le contexte. Nous avons tout à fait compris la nécessité de tout stopper. Nous nous sommes dit que c'était mieux ainsi, pour éviter tout danger. Malgré notre déception, car nous nous étions projetés dans la démarche, nous avions bien conscience que nous n'étions pas une priorité.

T1 Attente

Pendant le confinement, nous avons tenté de joindre le secrétariat une fois par téléphone et par mail, tout en sachant que nous appelions trop tôt vis-à-vis de l'évolution de l'épidémie et au regard des mesures prises au niveau national. La patience a peu à peu laissé place à l'interrogation, puis à l'envie de nous reconsacrer à notre projet de bébé dès le 11 mai, lorsque nous avons tous les deux repris le travail. L'attente est alors devenue plus lourde, car les délais ne nous étaient pas précisés.

T1 Impact psychologique

Pendant le confinement, nous étions préoccupés par la pandémie, ce qui nous a permis d'accepter la situation. Lors du déconfinement, il a été plus difficile psychologiquement de supporter l'absence d'une date de reprise, d'autant plus que des proches nous ont annoncé qu'ils attendaient un heureux événement. Nous sommes bien entourés et avons la possibilité de parler de notre vécu, de ce fait, nous avons réussi à tenir, malgré tout. Nous avons essayé de ne pas mélanger notre histoire avec celle des autres, de rester lucides.

T1 Point sur le projet d'AMP

Malgré quelques désillusions un peu frustrantes, nous restons très motivés et impatients de reprendre le protocole et de nous rapprocher au plus près de notre souhait de devenir parents.

Propos recueillis par Catherine Foulhy

Sage-femme

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