Vincent Caron
email: vincent.caron@u-picardie.fr

Julien Bailleul

Frank Chanier

Geoffroy Mahieux

Bartonian Limestones

FRENCH S T Bartholomew

Demise and recovery of Antillean shallow marine carbonate factories adjacent to active submarine volcanoes (Lutetian-Bartonian limestones, St. Bartholomew, French West Indies)

Keywords: Eocene, Caribbean, carbonate ramp, skeletal carbonates, volcaniclastics

Introduction

Volcanism may be intuitively regarded as critically detrimental to shallow-water benthic communities, and as such as one environmental parameter impacting the development of carbonate platforms. Lava flows and large pyroclastic eruptions, either subaqueous or reaching subtidal environments from emerged volcanoes, can undeniably result in mass mortality of carbonate producers and therefore cause carbonate production to cease [START_REF] Tomascik | Rapid coral colonization of a recent lava flow following a volcanic eruption, Banda Islands, Indonesia[END_REF][START_REF] Vroom | Effects of volcanic ash deposits on four functional groups of a coral reef[END_REF]. However, recent studies have shown that volcaniclastic influx may also allow carbonate-producing organisms with higher surviving capabilities to thrive, and may promote a change of benthic communities, prolonging the existence of carbonate factories [START_REF] Wilson | Siliciclastic and volcaniclastic influences on equatorial carbonates: insights from the Neogene of Indonesia[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF]. These biota prove to be adapted to post-eruption environmental conditions such as reduced luminosity and increased turbidity due to suspended ash, change of substrate, change of nutrient levels and of water chemistry through alteration of volcanic material [START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF]. It follows that volcanic events, even of short duration and/or limited in the volume of material delivered to the marine realm, may be diversely expressed in otherwise carbonate-dominated settings and ultimately in outcrops. Expected physical, stratal and facies expressions of volcaniclastic influx include: (1) erosion of the seafloor and of reefal buildups [START_REF] Wilson | Tertiary syntectonic carbonate platform development in Indonesia[END_REF]; (2) reduction of or temporarily arrested carbonate production; (3) deposition of volcaniclastic material; and (4) a change in the depositional systems and in the biotic assemblages [START_REF] Wilson | Siliciclastic and volcaniclastic influences on equatorial carbonates: insights from the Neogene of Indonesia[END_REF][START_REF] Dorobek | Carbonate-platform facies in volcanic-arc settings: Characteristics and controls on deposition and stratigtraphic development[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF][START_REF] Reuter | A Middle Miocene carbonate platform under silicivolcaniclastic sedimentation stress (Leitha Limestone, Styrian Basin, Austria) -Depositional environments, sedimentary evolution and palaeoecology[END_REF].

Herein, we propose a depositional model for Eocene tropical carbonates that formed in a volcanically active area, namely the Lesser Antilles Volcanic Arc, West Indies. Here, carbonate and mixed carbonate-volcaniclastic units are intercalated between volcaniclastics and lava flows, pointing to the repeated demise and foundering of carbonate factories, but also to the interplay between volcanic activity and penecontemporaneous carbonate production. This study is the first to document in detail the compositional characteristics of the Antillean carbonate successions on St. Barths Island.

Geological setting

The Lesser Antilles arc is related to the westward-dipping subduction zone where the oceanic crust of the American plate is underthrusting the Caribbean plate, hence causing important volcanic and seismic activities (Fig. 1A).

North of the Island of La Martinique, the Lesser Antilles arc consists of two divergent volcanic lines, namely the now extinct outer arc active from the early Eocene to middle Oligocene, and the still active inner arc [START_REF] Bouysse | The Lesser Antilles island arc[END_REF]. Owing to this evolution and subsequent uplift, the outer arc system became the locus of abundant carbonate production and accumulation during the late Paleogene and Neogene. It evolved into extended carbonate platforms that correspond to the so-called Limestone Caribbees, whereas to the west, intense volcanic activity led to the construction of an archipelago of islands referred to as the Volcanic Caribbees [START_REF] Bouysse | The Lesser Antilles island arc[END_REF].

The Island of St. Barths lies on the northeastern sector of the Lesser Antilles outer arc and belongs to the present-day platform. It consists predominantly of limestone beds intercalated between volcanics (Fig. 1B). The latter includes hyaloclastite deposits generated by hydroexplosions interbedded with andesitic and basaltic submarine lava-flows. Up to six limestone sheets from 3 up to 40 m thick have been recognized and previously interpreted as peri-reefal carbonates that were given a late middle Eocene (Lutetian and Bartonian) age on the basis of microfaunal content (Westercamp andAndreieff, 1983a, 1983b;[START_REF] Gradstein | The Geologic Time Scale 2012[END_REF]. This study concentrates on the limestone units and their under-and overlying contacts with volcanics.

Methods

Field and laboratory analysis

The bulk of information used in this study comes from field observation and description of 13 stratigraphic sections along the coasts of St. Barths and on two islets located southwest and southeast off the main island, namely Pain de Sucre and Île Coco, respectively (Figs. 1C,2).

Due to their common occurrence in the carbonate strata and locally in volcaniclastic units, and to their relative abundance in some horizons associated with key sedimentary surfaces, echinoid macrofossils were given special attention (Fig. 2). Field characteristics (diversity, abundance, orientation and preservation) of spatangoid (Schizaster L. Agassiz, Agassizia L. Agassiz and Desor, Eupatagus L. Agassiz, Antillaster Lambert) and oligopygoid (Haimea Michelin) echinoids in particular, were determined prior to being collected where possible for taxonomic identification. Echinoids include epibenthic dwellers and shallow to deep endobenthic burrowers [START_REF] Kier | Fossil Spatangoid Echinoids of Cuba[END_REF][START_REF] Kanazawa | Adaptation of test shape for burrowing and locomotion in spatangoid Echinoids[END_REF][START_REF] Donovan | Spatangoid echinoids from the Eocene of Jamaica[END_REF]. As such, echinoids are useful indicators of paleoenvironmental conditions, including trophic resources, absence/presence of seagrass beds, and substrate (Fig. 3). Characteristics of other dominant macrofossils, such as corals and pinnids, were also evaluated qualitatively in the field (living position, mechanical erosion, bioinfestation). In this study, the taxonomy of coralline algae uses at best generic names only. Genus circumscription follows [START_REF] Rasser | Application of neontological taxonomic concepts to Late Eocene coralline algae (Rhodophyta) of the Austrian Molasse Zone[END_REF] and [START_REF] Braga | Coralline algae (Corallinales, Rhodophyta) in western and central Mediterranean Messinian reefs[END_REF]. Family to subfamily names follow [START_REF] Harvey | Choreonema (Corallinales, Rhodophyta): 18S rDNA phylogeny and resurrection of the Hapalidiaceae for the subfamilies Choreonematoideae, Austrolithoideae, and Melobesioideae[END_REF]. Coralline algal growth-form terminology follows Woelkerling et al. (1993). The taxonomy of larger foraminifera is restricted to Family level and at best genus level except for those listed in Westercamp andAndreieff (1982, 1983).

The Eocene limestone units were analyzed petrographically using 110 thin-sections cut in samples selectively collected below and above sharp, erosive, and burrowed contacts. The aim was to provide estimates of the relative abundances of skeletal and non-skeletal constituents, and to assess facies changes across sedimentary surfaces. Results were converted for the dominant taxa at subfamily level and grain types into abundance indices of rare (one or two grains seen), occasional (about 10%), common (conspicuous throughout, i.e., 20-30%), and abundant (the grain category considered is the dominant skeletal component, i.e., ≥50%). The data obtained were used to determine the composition of the skeletal associations only, and are not suitable for statistical analysis. These qualitative data were complemented by textural information using the criteria of [START_REF] Embry | A late Devonian reef tract on northeastern Banks Island[END_REF]. In addition, a series of specific scales of taphonomic features have been defined for various fossil types observed in thin section to help assess the effects of early sea-floor processes, namely fragmentation, abrasion, bioerosion and encrustation (Fig. 4).

Skeletal associations

Because pervasive bioturbation has obliterated, but in a few examples, primary wave-and current-induced sedimentary structures, interpretation of the facies in terms of depositional conditions was based on comparative ecology and sedimentology with ancient and modern shallow marine environments (e.g., [START_REF] Hallock | Larger foraminifera: a tool for palaeoenvironmental analysis of Cenozoic depositional facies[END_REF][START_REF] Hottinger | Shallow benthic foraminiferal assemblages as signals for depth of their deposition and their limitations[END_REF][START_REF] Bassi | Coralline algal facies and their palaeoenvironment in the Late Eocene of Northern Italy (Calcare di Nago, Trento)[END_REF][START_REF] Bassi | Larger foraminiferal and coralline algal facies in an Upper Eocene storminfluenced, shallow-water carbonate platform (Colli Berici, north-eastern Italy)[END_REF][START_REF] Braga | Coralline algal assemblages in Upper Neogene reef and temperate carbonates in southern Spain[END_REF][START_REF] Hallock | Coral reefs, carbonate sedimentation, nutrients, and global change[END_REF][START_REF] Hohenegger | Displacement of larger Foraminifera at the western slope of Motobu Peninsula (Okinawa, Japan)[END_REF][START_REF] Beavington-Penney | Ecology of extant nummulitids and other larger benthic foraminifera: applications in palaeoenvironmental analysis[END_REF][START_REF] Hallock | Larger benthic foraminifers of the marion plateau, northeastern Australia (ODP leg 194): comparison of faunas from bryozoan (sites 1193 and 1194) and red algal (sites 1196-1198) dominated carbonate platforms[END_REF]Hohenneger, 2009;[START_REF] Payros | The Eocene storm-dominated foralgal ramp of the western Pyrenees (Urbasa-Andia Formation): An analogue of future shallow-marine carbonate systems?[END_REF]. Results of the petrographic analysis highlight a diverse array of biotic constituents and skeletal associations, which can satisfactorily be classified as chlorozoan, chloralgal and foramol [START_REF] Lees | Modern temperate water and warm water shelf carbonate sediments contrasted[END_REF][START_REF] Lees | Possible influence of salinity and temperature on modern shelf carbonate sedimentation[END_REF][START_REF] James | The cool-water carbonate depositional realm[END_REF], rhodalgal [START_REF] Carannante | Carbonate lithofacies as paleolatitude indicators: problems and limitations[END_REF], echinofor and foralgal [START_REF] Hayton | A skeletal assemblage classification system for nontropical carbonate deposits based on New Zealand Cenozoic limestones[END_REF]. Although chloralgal and chlorozoan associations dominated by zooxanthellate corals, calcareous green algae and non-skeletal carbonates (e.g., ooids, peloids and oncoids) are robust indicators of relatively oligotrophic clear sea waters inside the tropical climate belt, interpretation of the majority of skeletal associations in terms of temperature, climate and paleoecology needs to integrate additional palaeoenvironmental information such as nature of the substrate, siliciclastic fluxes and trophic resources (e.g., [START_REF] Hallock | Nutrient excess and the demise of coral reefs and the demise of coral reefs and carbonate platforms[END_REF][START_REF] Hallock | Why are larger foraminifera large?[END_REF][START_REF] Hallock | Fluctuations in the trophic resource continuum: a factor in global diversity cycles?[END_REF][START_REF] Allmon | Role of temperature and nutrients in extinction of turritelline gastropods: Cenozoic of the northwestern Atlantic and northeastern Pacific[END_REF]Brasier, 1995a, b;[START_REF] Pomar | Environmental factors influencing skeletal grain sediment associations: a critical review of Miocene examples from the western Mediterranean[END_REF][START_REF] Wilson | The apparent paradox of abundant foramol facies in low latitudes: their environmental significance and effect on platform development[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF][START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF].

Paleoenvironments and paleodepths

Although small isolated coral bioherms (patch-reefs s.l.) and coral carpets are present in some of the limestone units, the absence of major reefal constructions (e.g., barrier coral-reef) and the sedimentological characteristics of facies within the St. Barths limestones suggest that the general depositional setting was a carbonate ramp (i.e., following the terminology of [START_REF] Burchette | Carbonate ramp depositional systems[END_REF] attached to and/or surrounding the flanks of active submarine volcanoes. The subdivision of the carbonate ramp system into inner, middle and outer ramp depositional settings follows the criteria proposed by [START_REF] Pomar | Ecological control of sedimentary accommodation: evolution from carbonate ramp to rimmed shelf, Upper Miocene, Balearic Islands[END_REF]. The term inner ramp refers to depositional environments between upper shoreface (i.e., the zone of breaking waves or lagoonal shorelines) and Fair-Weather Wave Base (FWWB), middle ramp between FWWB and Storm-Wave Base (SWB), and outer ramp below SWB [START_REF] Burchette | Carbonate ramp depositional systems[END_REF]. The division of photic zones with respect to water depths is based on the criteria of [START_REF] Pomar | Ecological control of sedimentary accommodation: evolution from carbonate ramp to rimmed shelf, Upper Miocene, Balearic Islands[END_REF]. The low-light conditions can be inferred from the absence or very rare co-occurrences of miliolids and calcareous green algae (dasycladaleans), which typically are indicative of inner ramp environments when they are the dominant biotic constituents [START_REF] Geel | Recognition of stratigraphic sequences in carbonate platform and slope deposits: empirical models based on microfacies analysis of Palaeogene deposits in southeastern Spain[END_REF]Zamagni et al., 2008).

The presence and abundance of taxa indicative of specific depth constraints known from modern environments and interpreted from ancient deposits were only used to discriminate between euphotic and oligophotic conditions [START_REF] Pomar | Ecological control of sedimentary accommodation: evolution from carbonate ramp to rimmed shelf, Upper Miocene, Balearic Islands[END_REF]. Shallow-water biotic indicators include zooxanthellate corals, pinnid bivalves, miliolids, conical agglutinated foraminifera and seagrass dwellers such as small benthic rotaliids [START_REF] Geel | Recognition of stratigraphic sequences in carbonate platform and slope deposits: empirical models based on microfacies analysis of Palaeogene deposits in southeastern Spain[END_REF][START_REF] Vecchio | Agglutinated conical foraminifera from the Lower-Middle Eocene of the Trentinara Formation (southern Italy)[END_REF]. The estimation of paleodepth using trends in test flattening of larger benthic foraminifera, combined with textural attributes of host sediments, namely siliciclastic content, grain size, and presence of carbonate/argillaceous mud [START_REF] Hohenegger | Remarks on West Pacific Nummulitidae (Foraminifera)[END_REF][START_REF] Beavington-Penney | Ecology of extant nummulitids and other larger benthic foraminifera: applications in palaeoenvironmental analysis[END_REF][START_REF] Cosovic | Paleoenvironmental model for Eocene foraminiferal limestones of the Adriatic carbonate platform (Istrian Peninsula)[END_REF][START_REF] Hohenegger | Functional shell geometry of symbiont-bearing foraminifera[END_REF], suggests deposition in inner-to outer-ramp settings for amphisteginids-and nummulitids-bearing deposits. Foralgal associations that include coralline algae, such as dominant melobesioids (Lithothamnion, Mesophyllum) and subordinate mastophoroids (Lithoporella) with rare sporolithales (Sporolithon) are generally associated with middle-ramp to outer ramp settings [START_REF] Nebelsick | Diversity, growth forms and taphonomy: key factors controlling the fabric of coralline algae dominated shelf carbonates[END_REF][START_REF] Braga | Coralline algal assemblages in Upper Neogene reef and temperate carbonates in southern Spain[END_REF][START_REF] Pomar | Environmental factors influencing skeletal grain sediment associations: a critical review of Miocene examples from the western Mediterranean[END_REF]. The abundance of flattened orthophragminids and planktic foraminifera points to distal middle ramp to outer ramp settings [START_REF] Bassi | Larger foraminiferal and coralline algal facies in an Upper Eocene storminfluenced, shallow-water carbonate platform (Colli Berici, north-eastern Italy)[END_REF]Zamagni et al., 2008).

Changes in the depositional environments and in water depth thresholds for photodependent biota are however to be expected in the immediate aftermath of volcanic eruptions due to clastic influx and ash suspended in water [START_REF] Wilson | Siliciclastic and volcaniclastic influences on equatorial carbonates: insights from the Neogene of Indonesia[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF][START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF][START_REF] Reuter | A Middle Miocene carbonate platform under silicivolcaniclastic sedimentation stress (Leitha Limestone, Styrian Basin, Austria) -Depositional environments, sedimentary evolution and palaeoecology[END_REF].

Description of volcaniclastic deposits

Volcaniclastic deposits represent the products of submarine eruptive episodes (Westercamp and Andreieff, 1983a), and include a basal ensemble of arc tholeiites and an upper ensemble of calcalkaline series (Fig. 1B-C). Volcaniclastic deposits range in thickness from several tens of meters to hundreds of meters. They are dominated by maar-type breccia (Vbr), coarse-grained hyaloclastites (Hy), and medium-to fine-grained tuffs (Tu), in a proximal to distal distance gradient from eruptive centers.

Coarse volcaniclastic breccia (Vbr) are massive to crudely bedded and contain heterometric angular clasts ranging in size from gravel to boulder, in a coarse-grained tuffitic matrix. These deposits are generally azoic, but may contain limestone clasts and coral heads reworked from underlying limestone units (Fig. 5A-B).

Lithologies of coarse-grained hyaloclastites (Hy) and fine-to medium-grained tuffs (Tu) are highly variable (see Westercamp and Andreieff, 1983b). The former can be subdivided into two major groups, based on bedding structure and clast shape.

The first group (Hy1) consists of horizontal and low-angle tabular, fining-upward, dm-thick beds having erosional bases. The basal contact is overlain by gravel-to cobble-sized (sub-)angular volcanic clasts in a poorly-sorted sandy/gravely matrix that grades into moderately sorted volcanic sands (Fig. 5C).

The second group (Hy2) represents reworked hyaloclastites (Fig. 5D-E). The deposits conformably overlie mixed carbonate-volcaniclastic limestones and exhibit alternating poorly/moderately-sorted conglomeratic beds that contain sub-rounded coarse sand-to pebblesized volcanic clasts, and moderately-sorted coarse-grained volcaniclastic sandstones (Fig. 5E).

Bioclasts and macrofossils, including bivalves, gastropods, bryozoans, fragmented coral branches and echinoids are common in the deposits. Tuffs (Tu) include cm-and dm-thick tabular beds of silty to sandy, moderately-to well-sorted deposits (Fig. 5F). Tuffs may be bioturbated and fossiliferous, with larger benthic foraminifera, solitary corals, and spatangoids.

Carbonate facies description

A total of 15 facies have been distinguished that point to various environmental and hydrodynamic conditions (Table 1). Features common to all facies are that none contain ooids or evaporitic features.

Mixed carbonate-volcaniclastic facies association (Mf1 to Mf5)

The abundance of volcaniclastic, tuffitic, feldspar crystals and quartz grains characterize this facies association. It can be subdivided into five major facies depending on the characteristics of volcaniclastic components and on the biotic/non-skeletal carbonate particle content. Tuffitic sediments, angular/subangular volcaniclastic fine sand to granule sized-debris and quartz fine-to medium sand represent 20% to 50% of the sediment fraction.

Smaller foraminiferal -dasycladalean -coral photozoan mixed facies (Mf1 and Mf2)

Two biotic associations comprise this facies. Mf1 is a smaller foraminiferal-dasycladalean association, and includes moderately-to well-cemented wackestones/floatstones, packstones and more rarely grainstones. Mf2 includes dasycladalean-coral floatstones and coral boundstones.

Intense bioturbation produces a typical nodular aspect to facies Mf1 and Mf2 beds, though massive bedding also occurs. Facies Mf1 and Mf2 strata may either overlie volcaniclastic units across sharp and gradational contacts, or carbonate beds across sharp undulating and erosional surfaces penetrated by Thalassinoides burrows.

In general, facies Mf1 is characterized by a low-diversity biota with a relative abundance of smaller benthic foraminifera, and subordinate miliolids and dasycladalean algae (Fig. 6A).

Peloids may be common to abundant, and micritized grains are generally present. Agglutinated conical foraminifera and laminar crusts of coralline red algae (Lithoporella) are occasional to common (Fig. 6B). Other organisms, such as echinoids (Eupatagus, Antillaster), thin-walled gastropods, bivalves, branching corals in living position and rare amphisteginids are also present.

Macrofossils and microfossils in micritic floatstones and wackestones/packstones show low to moderate degrees of fragmentation and abrasion, low degrees of encrustation and moderate degrees of bioerosion, except for corals which may be intensely bored. Grainstones typically exhibit higher degrees of fragmentation and abrasion, lower encrustation, and similar bioinfestion of skeletal grains.

Facies Mf2 differs from Mf1 facies in being dominated by branching corals, which occur as sparfilled moulds in a micritic matrix and constitute coral boundstones that locally build up small patchreef frameworks. Thick-shelled gastropods, dasycladalean algae and miliolids may be common. Large photosymbiont-bearing foraminifera are rare to common in places and include amphisteginids and nummilitids. Agglutinated conical foraminifera and echinoid fragments are present in small amounts. Other fossils include epifaunal spatangoids such as Antillaster.

Skeletons in facies Mf2 show low to moderate degrees of fragmentation and abrasion leaving gastropods with their tubercules left intact for example. Corals are commonly partly micritized and encrusted by cyanobacterial micritic laminae.

Echinoid -Red algal photozoan facies (Mf3)

Textural attributes of facies Mf3 are variable and range from wackestone to packstone/grainstone (Fig. 6C). Massive bedding is typical, although nodular bedding also occurs pointing to intense bioturbation that likely obliterated primary sedimentary structures. Facies Mf3 is characterized by low-diversity biogenics with a relative abundance of echinoids (plates and spine fragments) and fragments of rhodoliths, branches and laminar crusts. Larger foraminifera are unusual, but when present consist predominantly of orthophragminids, and rare nummulitids and amphisteginids. Micritic grains, such as peloids and cortoids, may be abundant.

Subordinate biogenics include bivalves and corals. Intraclasts are present and consist of skeletal grains bearing rims of palisadic spar crystals with scalenohedral terminations and echinoid plates with dirty spar syntaxial overgrowths. Facies Mf3 has moderate to high degrees of fragmentation and abrasion, and relatively low to moderate degrees of bioerosion and encrustation.

Mixed larger foraminiferal -mollusk photozoan facies (Mf4)

The massive beds of facies Mf4 are sharp-based. Mollusks, larger ovate nummulitids, amphisteginids and agglutinated conical foraminifera with particularly high amounts of coarse sand to granule sized-volcaniclastics dominate these sediments. Volcaniclastic grains are subangular and poorly-to moderately-sorted. Coral and coralline algal debris, and bryozoans are occasional to common and typically show moderate to high degrees of fragmentation and abrasion, little if any encrustation, and low bioerosional features. Echinoids are generally found fragmented and include sand-dwellers Eupatagus, Meoma and Haimea (Fig. 3). Sedimentary structures vary from planar bedding to sigmoidal and hummocky cross-stratifications. Facies textures are volcaniclastic rudstones with a packstone and/or grainstone matrix.

Mixed Bioclastic -peloidal facies (Mf5)

Beds of facies Mf5 are either massive with a wavy basal contact or nodular grading from underlying volcaniclastic deposits across a transitional interval of carbonate nodules in an argillaceous matrix. Moderately to well-sorted silt and fine sand-sized bioclastic and tuffitic material dominate this facies (Fig. 6D). The carbonate fraction consists predominantly of peloids originating in micritized skeletal fragments, such as red algal debris, and of cortoids in a packstone matrix. Subordinate components include fragmented benthic foraminifera, echinoid plates and spines, and corals. Thin-shelled disarticulated bivalves may be present. Fragmentation and abrasion are moderate, bioerosion is high and encrustation is rare.

Dasycladalean -miliolid photozoan facies (DaMi)

Beds of facies DaMi are massive. Wackestones and packstones are the dominant textures (Fig. 6E). Facies DaMi is similar to mixed facies Mf1 and Mf2, but is free of volcaniclastic content. Smaller benthic foraminifera are common, and are associated with common to abundant miliolids, dasycladalean algae and peloids. Accessory components include micritized grains (cortoids), bivalves, agglutinated conical foraminifera (Heterodictyoconus), and occasional amphisteginids. Laminar crusts of melobesioids are locally present. Rocks of facies DaMi contain common branching corals and articulated bivalves in living position. Degrees of fragmentation and abrasion are generally low, and bioerosion and encrustation are moderate to high.

Larger benthic foraminiferal -coralline algal facies (LfRh, LfCa)

This biotic association consists of packstones, rudstones and bindstones. Coralline algae are represented by members of the subfamilies Mastophoroids (Lithoporella), Melobesioids (Mesophyllum, Lithothamnion) and Sporolithalean (Sporolithon). Larger foraminifera are present in all facies and are represented by amphisteginids, nummulitids (Nummulites), orthophragminids such as Discocyclina, Pseudophragmina and Asterocyclina, and by the lepidocyclinid Polylepidina. Accessory components comprise small benthic foraminifera (textulariids, miliolids), encrusting foraminifera (acervulinids), fragments of bryozoans, bivalves, and corals. Echinoid plates are locally common. Non-skeletal carbonates (peloids, oncoids, cortoids) are generally present and may be abundant in places.

Larger benthic foraminiferal -rhodolith photozoan facies (LfRh1 to LfRh3)

These facies consist of coarse-grained packstones, sparitic rudstones/grainstones and rare bindstones dominated by larger benthic foraminifera and coralline red algae. Decimeter-thick beds have wavy bedding planes and are intensely bioturbated, resulting in a typical nodular texture. Medium-scale (up to 1 m large and dm deep) trough cross-stratifications and low-to high-angle foresets are locally present. The larger foraminiferal assemblage of facies LfRh1 consists of common amphisteginids, rare to occasional nummulitids, and lepidocyclinids. Facies LfRh2 is a nummulitid-lepidocyclinid packstone-rudstone. Fragments of fruticose coralline thalli and rhodoliths are also present in both facies and may be common to abundant within the carbonate matrix. In addition, other biogenic components include occasional textulariids, rare miliolids, occasional mollusks dominated by epifaunal bivalves, occasional coral fragments and planktonic foraminifera. Peloids and cortoids range in abundance from rare to common. Coralline bindstones are present locally in facies LfRh2 as intraclasts. The binding structure is composed of laminar coralline thalli 0.5-1.0 mm thick and cyanobacterial laminae with a stromatolithic texture. Mastophoroids (Lithoporella) and sporolithalean (Sporolithon) are present in facies LfRh1, and rare to absent in facies LfRh2 and LfRh3. Facies LfRh3 is dominated by rhodoliths in a bioclastic grainstone matrix composed of common echinoid plates and peloids, occasional larger benthic foraminifera, mollusks, corals, and dasycladalean algae (Fig. 6F).

Rhodoliths in facies LfRh 1 and LfRh2 are variable in size with a mean diameter from 1 to 10 cm, and are typically dispersed within a coarse-grained grainstone matrix. Coalescence of two rhodoliths has been observed. Rhodoliths in facies LfRh3 are more homogeneous in size ranging from 1-5 cm. The most common rhodolith morphology is sub-spheroidal with a dense inner laminar arrangement of coralline thalli. Epifaunal macrofossils include irregular echinoids Haimea and Antillaster, and large thick-shelled oysters, which may locally be abundant in facies LfRh1.

There is no significant difference between facies LfRh1, LfRh2 and LfRh3 in their degree of taphonomic alteration. Each facies consists of a mixture of poorly to highly altered skeletal material with respect to fragmentation, abrasion and bioerosion. Encrusters include red algae, serpulids, foraminifera, and cyanobacteria.

Larger benthic foraminiferal -coralline algal photozoan facies (LfCa1 and LfCa2)

Facies LfCa1 and LfCa2 consist of massive-to nodular-bedded larger foraminiferal-red algal packstones and grainstones. Basal contacts are either gradational or sharp. Underlying strata are mixed carbonate-volcaniclastic and carbonate units. The main components are coralline algal branches, less than 1 cm-sized rhodoliths, and their debris, and larger benthic foraminifera.

Among the latter, amphisteginids and subordinate nummulitids dominate facies LfCa1 (Fig. 6G), whereas nummilitids associated with orthophragminids are abundant in facies LfCa2 (Fig. 6H).

Other dominant components include echinoid plates and spines, smaller benthic foraminifera (rotaliids and occasional textulariids), and peloids and micritized skeletons. Subspheroid rhodoliths (up to 3 cm in diameter) may also be present. Coralline branches and debris consist mostly of melobesioids and occasional mastophoroids (Lithoporella).

The foraminiferal assemblage is dominated by Amphistegina and Nummulites in LfCa1, and Nummulites, Discocyclina and Pseudophragmina in LfCa2.

Skeletal material in facies LfCa1 has lower degrees of alteration than its counterpart in facies LfCa2. In the latter, coralline thalli and larger foraminifera exhibit a wide range of alteration from low to high for fragmentation, abrasion, bioerosion and encrustation, pointing to the mixing of fresh and older skeletons, i.e., exposed for longer periods of time to destructive processes.

Echinoid facies associations (EcF1 and EcF2)

Facies EcF1 are well-cemented packstones and grainstones containing abundant echinoid fragments, common peloids and subordinate larger benthic foraminifera (Fig. 6I). Beds of facies EcF1 are massive to nodular with sharp basal contacts. Facies EcF2 are semi-lithified packstones and wackestones rich in small benthic foraminifera (rotaliids), and comprise a complex assemblage of echinoid macrofossils. Decimeter-thick beds of facies EcF2 generally overlie wavy surfaces pervasively bioturbated by Thalassinoides.

Echinoid -non-skeletal carbonate photozoan facies (EcF1)

Irregular echinoids, including spatangoids (Haimea) and cassiduloids (Echinolampas) are common in these rocks. Branching zooxanthellate corals in growth position are ubiquitous at some localities. Gastropods and disarticulated bivalves are present. The fine-to medium-sand sized biogenic particles comprise common to abundant echinoid plates (Fig. 6I), occasional larger benthic foraminifera, particularly amphisteginids and nummulitids, molluskan fragments, geniculate and non-geniculate coralline debris, and less common miliolids, small agglutinated foraminifera, coral debris, and bryozoans. Peloids are common to abundant. Frequent presence of micritized skeletons suggests that the majority of peloids may be small micritized grains.

Degrees of fragmentation and abrasion are moderate to high, and common micritization indicates that bioinfestation is pervasive. Encrustation of coral fragments and mollusks is low to moderate, and involves cyanobacteria, red algae and foraminifera.

Echinoid -smaller benthic foraminiferan photozoan facies (EcF2)

The co-occurrence of spatangoids, cassiduloids, and oligopygoids with different living habitats and substrate dependencies is frequent in facies EcF2 deposits. The co-occurrence of Haimea, Schizaster, Agassizia, Eupatagus, and Echinolampas provides an example of such complex diverse echinoid assemblages (Fig. 3) that point to contrasted depositional conditions over time.

Results show that about 30% echinoids are in living position, a majority of which (80%) being represented by shallow (Agassizia) and deep (Schizaster) infaunal dwellers. Other macrofossils include large thick-shelled gastropods and pinnid bivalves dispersed in the deposits. Foraminifera comprise the porcelaneous and hyaline smaller benthic majority. Larger forms are occasional.

Coralline fragments are rare and tend to be dominated by geniculate forms. Small agglutinated foraminifera, mollusks, miliolids, and calcispheres are occasional. Peloids may be abundant, whereas cortoids and oncoids are unusual. Volcaniclastic content is low.

The skeletal fraction has moderate to high degrees of fragmentation and abrasion, low to moderate degrees of bioerosion and encrustation. However, echinoid plates are typically less affected by destructive processes than other skeletons.

Coral photozoan facies (CoP1 and CoP2)

Two facies that reflect different biohermal geometries, hydrodynamic conditions and coral shapes are present. Members of the genera Astrocoenia, Hydnophora, and Cladocora have been identified. Small bioherms with lenticular geometry, a few meters large and up to 2-4 m high, and coral carpets characterize facies CoP1. Branching and platy corals in growth position constitute the coral framework. Corals are enclosed in a peloidal-micritic matrix. Other components include encrusting coralline algae, gastropods and small benthic foraminifera. Meter-sized lenticular bioherms exhibit several growth-phases, each one being laterally correlated to tabular beds of facies Mf2, EcF2, and DaMi (Fig. 7A), a geometry that reflects a strong interaction between biohermal building and ambient sedimentation [START_REF] Gaillard | Les biohermes à spongiaires et leur environnement dans l'Oxfordien du Jura méridional[END_REF]. Massive coral framework and biohermal rudstones compose facies CoP2. Individual biohermal structures are up to 6-8 m-high.

Massive dendroid corals in living position dominate in the upper half part of the constructional bodies (Fig. 7B). Pebble to cobble-sized reef debris constitute lateral correlatives of the coral build-ups and are deposited as structureless up to 1 m-thick beds intercalated between tabular and nodular beds of facies EcF1 and LfCa1. The base of the coral build-ups appear sharp and possibly erosional (Fig. 7B), though not confirmed by field observation, a discrepancy that may originate in differential compaction and diagenesis [START_REF] Rusciadelli | Differential compaction as control on depositional architectures across the Maiella carbonate platform margin (central Appenines, Italy)[END_REF][START_REF] Berra | Differential compaction and early rock fracturing in high-relief carbonate platforms : numerical modelling of a Triassic case study (Esino limestone, central southern Alps, Italy)[END_REF].

Carbonate facies interpretation

The virtual absence of silty micrite-rich planktonic foraminifera-dominated facies indicates that St. Barths Eocene carbonates and mixed carbonate-volcaniclastic sediments were principally deposited in inner to middle ramp settings [START_REF] Nebelsick | Facies dynamics in Eocene to Oligocene circumalpine carbonates[END_REF]. In addition, the rare to occasional occurrence of symbiont-bearing larger benthic foraminifera with flattened shapes (orthophragminids, lepidocyclinids), a morphological adaptation to maximize light collection in otherwise oligophotic conditions below wave influence [START_REF] Hallock | Larger foraminifera: a tool for palaeoenvironmental analysis of Cenozoic depositional facies[END_REF][START_REF] Beavington-Penney | Ecology of extant nummulitids and other larger benthic foraminifera: applications in palaeoenvironmental analysis[END_REF][START_REF] Hohenegger | Functional shell geometry of symbiont-bearing foraminifera[END_REF], and of light-independent biota-dominated facies confirm that the studied deposits are representatives of inner ramp and proximal to possibly distal middle ramp facies belts. Figure 8 proposes a reconstruction of the depositional environments envisaged for the St. Barths carbonate facies. We must emphasize that different microfacies associated with identical parts of the carbonate ramp may not have all developed contemporaneously, even though a mosaic of subenvironments, each being characterized by specific ecological attributes in relation to subtle or major changes in substrate, nutrient levels, water depth, salinity and/or other parameters, should be expected in settings influenced by volcanism, subsequent influxes of volcaniclastics and resulting environmental stresses.

Inner ramp: shallow back barrier setting and patch reefs

Biogenic assemblages dominated by euphotic taxa, sedimentary structures comprising thin and planar beds, and micritic textures of facies Mf1, Mf2, Mf5, DaMi, CoP1 and EcF2 (Table 1) are interpreted to signal shallow-water inner ramp environments. The abundance of smaller benthic foraminifera, including textulariids, the common occurrence of dasycladal algae, miliolids, agglutinated conical foraminifera, and the rarity of hyaline larger foraminifera in facies Mf1 suggest light-level conditions of the upper euphotic zone [START_REF] Murray | Ecology and distribution of benthic foraminifera[END_REF][START_REF] Geel | Recognition of stratigraphic sequences in carbonate platform and slope deposits: empirical models based on microfacies analysis of Palaeogene deposits in southeastern Spain[END_REF]Zamagni et al., 2008). The presence of delicate laminar crusts of mastophoroid coralline algae, which appear detached from their substrate and commonly exhibit hook and ring shapes (Fig. 6E), together with common calcareous green algae fragments and smaller benthic foraminifera hint for the existence of seagrass beds in the depositional environment [START_REF] Sola | Hooked and tubular coralline algae indicate seagrass beds associated to Mediterranean Messinian reefs (Poniente Basin, Almería, SE Spain)[END_REF].

The local abundance of coral colonies constructing isolated bioherms, the presence of larger foraminifera and the occasional occurrence of smaller benthics suggest normal marine salinities such as in facies Mf2 and DaMi.

Fossils of these facies and their taphonomic attributes, together with wackestone and packstone textures and sedimentary structures, indicate low-energy hydrodynamic conditions in shallow-water. The abundance of miliolids, together with spatangoids Schizaster and Brissoides (Fig. 3) points to soft fine-sand and muddy substrates. The abundance of volcaniclastics in mixed facies likely resulted in coarser substrates favorable to epifaunal and shallow endofaunal dwellers, such as Antillaster and Eupatagus [START_REF] Kanazawa | Adaptation of test shape for burrowing and locomotion in spatangoid Echinoids[END_REF][START_REF] Donovan | Spatangoid echinoids from the Eocene of Jamaica[END_REF]. Although the final depositional setting for facies EcF2 sediments is interpreted to be a shallow protected environment (i.e., occurrence of spatangoid dwellers and mud-dominated deposits), the diverse echinoid assemblage pointing to varied palaeoecological modes (i.e., from sand to muddy substrates; Fig. 3) associated with high fragmentation and abrasion indices of the bioclastic fraction implies a complex depositional history from high/moderate-to low-energy hydrodynamic conditions.

Abundance of volcaniclastic elements in carbonate strata overlying volcaniclastic units across erosive surfaces (see discussion below) suggests reworking of underlying beds through wave action.

Open inner ramp to middle ramp: wave-dominated settings

Open inner ramp and transitional environments to middle ramp settings are dominated by wave action. The influence of currents and high-energy waves can be deduced from the lack of easily winnowed silts and micrite, relatively coarse grain sizes, moderate to high degrees of fragmentation and abrasion of skeletons and lithoclasts, and cross-stratifications. In addition, robust coral morphologies and overall thick-walled skeletons more resistant to wave-induced transportation and to waterborne projectiles constitute useful indicators of strong hydrodynamic conditions [START_REF] Hughes | Skeletal density and growth form of corals[END_REF].

Representative of inner ramp to middle ramp facies belts are facies LfRh1, LfCa1, Mf4, EcF1 and CoP2 (Table 1). With the exception of chlorozoan facies (CoP2), most facies are characterized by diverse faunal assemblages with varied degrees of alteration.

The dominance of biotic assemblages with robust larger foraminifera (Amphistegina, Nummulites, and subordinate Discocyclina), coralline algal branches, subspheroid rhodoliths, togehther with the presence of zooxanthellate corals and smaller benthic foraminifera, miliolids and dasycladal algae, indicate deposition within the euphotic zone [START_REF] Pomar | Ecological control of sedimentary accommodation: evolution from carbonate ramp to rimmed shelf, Upper Miocene, Balearic Islands[END_REF][START_REF] Nebelsick | Facies dynamics in Eocene to Oligocene circumalpine carbonates[END_REF]Afzar et al., 2011). The common occurrence of larger foraminifera argues against high nutrient levels, since these foraminifera thrive in mesotrophic to principally oligotrophic waters [START_REF] Hottinger | Shallow benthic foraminiferal assemblages as signals for depth of their deposition and their limitations[END_REF][START_REF] Langer | Biogeography of selected larger foraminifera[END_REF][START_REF] Halfar | Nutrient and temperature controls on modern carbonate production: An example from the Gulf of California, Mexico[END_REF].

Constituents of these coarse-grained facies (packstones, grainstones and sparitic rudstones) possess moderate to high degrees of fragmentation and abrasion consistent with relatively highenergy deposition above FWWB [START_REF] Burchette | Carbonate ramp depositional systems[END_REF]. Particularly, the common occurrence of broken, poorly-preserved and abraded larger foraminifera not only provides evidence of high-energy conditions, but also may indicate repetitive burial and exhumation due to frequent physical reworking [START_REF] Beavington-Penney | Analysis of the effects of abrasion on the tests of Palaeonummulites venosus: implications for the origin of nummulithoclastic sediments[END_REF].

Low-to high-angle cross-stratifications may represent internal structures of subaqueous skeletal dunes that developed through the reworking of bottom sediments including inner ramp protected smaller foraminiferal -miliolid -dasycladalean sediments and deeper, more open, hyaline foraminiferal -coralline algal deposits. Sigmoidal and hummocky cross-stratifications record wave-dominated hydrodynamic conditions [START_REF] Dumas | Origin of hummocky and swaley cross-stratifications. The controlling influence of unidirectional current strength and aggradation rate[END_REF][START_REF] Tinterri | Combined flow sedimentary structures and the genetic link between sigmoidal-and hummocky-cross stratification[END_REF].

Similar inner to middle ramp packstones and grainstones dominated by larger foraminifera and coralline algae with comparable sedimentary attributes and occasional coral occurrences have been documented in south-east Asia from Eocene to middle Miocene limestones [START_REF] Adams | The foraminifera and stratigraphy of the Melinau Limestone, Sarawak, and its importance in Tertiary correlation[END_REF][START_REF] Wilson | Tertiary syntectonic carbonate platform development in Indonesia[END_REF][START_REF] Wilson | Cenozoic carbonates in Southeast Asia: implications for equatorial carbonate development[END_REF][START_REF] Wilson | Siliciclastic and volcaniclastic influences on equatorial carbonates: insights from the Neogene of Indonesia[END_REF], in the Indus Basin from Paleogene limestones [START_REF] Afzal | Dynamic response of the shallow marine benthic ecosystem to regional and pan-Tethyan environmental change at the Paleocene Eocene boundary[END_REF], and in other Paleogene western Tethyan deposits (e.g., [START_REF] Loucks | Regional depositional setting and pore network systems of the El Garia Formation (Metlaoui Group, Lower Eocene), offshore Tunisia[END_REF] for example. In the Caribbean realm, the middle Eocene Swanswick Formation of the White Limestone Group of Jamaica contains a diverse larger foraminiferal-algal assemblage with common echinoderm and molluskan fragments that [START_REF] Mitchell | Lithostratigraphy and palaeogeography of the White Limestone Group[END_REF][START_REF] Mitchell | Stratigraphy of the White Limestone of Jamaica[END_REF] similarly interpreted as open marine high-energy platform deposits.

Distal middle ramp facies belt: episodic wave influence

Middle ramp deposits are represented by foralgal and rhodalgal associations of facies LfRh2, LfRh3, Mf3, and LfCa2 (Table 1). The dominance of wackestones and packstones, and subordinate grainstones are compatible with low-energy conditions allowing settlement of fine particles, alternating with episodes of high-energy wave events [START_REF] Burchette | Carbonate ramp depositional systems[END_REF][START_REF] Nebelsick | Facies dynamics in Eocene to Oligocene circumalpine carbonates[END_REF][START_REF] Afzal | Dynamic response of the shallow marine benthic ecosystem to regional and pan-Tethyan environmental change at the Paleocene Eocene boundary[END_REF]. Abraded rhodoliths and the common occurrence of algal debris, and other bioclastic, material are supportive of current or wave reworking. Similar features have been recognized in open marine platforms influenced by sporadic storms [START_REF] Lund | Coralline algal nodules off Fraser Island eastern Australia[END_REF], and fossil examples have been described from Cenozoic successions (Braga and Martin, 1988;[START_REF] Bassi | Larger foraminiferal and coralline algal facies in an Upper Eocene storminfluenced, shallow-water carbonate platform (Colli Berici, north-eastern Italy)[END_REF][START_REF] Barattolo | Upper Eocene larger foraminiferal-coralline algal facies from the Klokova Mountain (southern continental Greece)[END_REF][START_REF] Payros | The Eocene storm-dominated foralgal ramp of the western Pyrenees (Urbasa-Andia Formation): An analogue of future shallow-marine carbonate systems?[END_REF]. The regime of waves and currents is an important factor that determines the shape and internal structure of rhodoliths (e.g., [START_REF] Freiwald | Sedimentological and biological aspects in the formation of branched rhodoliths in northern Norway[END_REF][START_REF] Marrack | The relationship between water motion and living rhodolith beds in the southwestern Gulf of California, Mexico[END_REF]. As such, the coalescence of rhodoliths (Fig. 6F) suggests times of relative hydrodynamic quiescence between episodes of turbulence preventing burial by fine sediments. The coralline algal assemblages are dominated by melobesioids with accessory mastophoroids and sporolithaceans. Compared to facies interpreted as inner ramp deposits, there is a taxonomic variation corresponding to a relative decrease in mastopohoroids (Lithoporella) and sporolithaleans (Sporolithon), and an increase in melobesioids (Lithothamnion). Such taxonomic changes in coralline assemblages showing a depth gradient have fossil analogues [START_REF] Rasser | Coralline red algal limestones of the Late Eocene Alpine Foreland Basin in Upper Austria: component analysis, facies and paleoecology[END_REF][START_REF] Braga | Coralline algal assemblages in Upper Neogene reef and temperate carbonates in southern Spain[END_REF][START_REF] Aguirre | The role of rhodoliths and rhodolith beds in the rock record and their use in palaeoenvironmental reconstructions[END_REF] and have been documented in modern settings [START_REF] Iryu | Distribution of marine organisms and its geological significance in the modern reef complex of the Ryukyu Islands[END_REF]. A distal middle ramp setting is compatible with the foraminiferal assemblage dominated by nummulitids and orthophragminids, with subordinate lepidocyclinids, rare amphisteginids and occasional planktonic foraminifera [START_REF] Nebelsick | Facies dynamics in Eocene to Oligocene circumalpine carbonates[END_REF]. In addition, the occasional occurrence of flattened test morphologies but also of lightdependent organisms, and the abundance of coralline algae suggest depositional conditions below FWWB and above SWB [START_REF] Hottinger | Shallow benthic foraminiferal assemblages as signals for depth of their deposition and their limitations[END_REF][START_REF] Hohenegger | Remarks on West Pacific Nummulitidae (Foraminifera)[END_REF][START_REF] Bassi | Larger foraminiferal and coralline algal facies in an Upper Eocene storminfluenced, shallow-water carbonate platform (Colli Berici, north-eastern Italy)[END_REF][START_REF] Hohenegger | Functional shell geometry of symbiont-bearing foraminifera[END_REF].

Discussion

Specific to carbonate systems is that any significant change of either one of the parameters, (e.g., trophic resources, depth of light penetration, turbidity, nature of substrate, etc.) influencing carbonate factories will result in either temporary or prolonged halts in carbonate production and accumulation in different sectors of the shelf [START_REF] Wilson | Tertiary syntectonic carbonate platform development in Indonesia[END_REF][START_REF] Wilson | Siliciclastic and volcaniclastic influences on equatorial carbonates: insights from the Neogene of Indonesia[END_REF][START_REF] Wilson | The apparent paradox of abundant foramol facies in low latitudes: their environmental significance and effect on platform development[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF][START_REF] Reuter | A Middle Miocene carbonate platform under silicivolcaniclastic sedimentation stress (Leitha Limestone, Styrian Basin, Austria) -Depositional environments, sedimentary evolution and palaeoecology[END_REF]. St. Barths limestones record the repeated collapse and renewal of carbonate production, as a result of episodic volcaniclastic material input (see below; Figs. 9, 10).

Demise of carbonate factories

Submersion and drowning caused by relative sea-level changes, environmental deterioration and burial by clastics are major controls on the demise of tropical carbonate platforms [START_REF] Schlager | Drowning unconformities on carbonate platforms[END_REF]. Termination of St. Barths carbonate factories relates to volcaniclastic input with accumulation rates exceeding rates of skeletal carbonate production and reef building until burial.

Erosional and sharp sedimentary surfaces between carbonate deposits below and volcaniclastic above are the dominant stratigraphic expressions identified in the studied successions for the demise of carbonate factories (Figs. 11A-D, 12).

Erosional surfaces are overlain by polymictic matrix-supported breccias (Facies Vbr), and represent syneruptive surfaces generated by the discharge of coarse volcanic material in the carbonate realm (Figs. 2B, 5B, 10A, 11A-B) [START_REF] Trofimovs | Submarine pyroclastic deposits formed at the Soufrière Hills volcano, Montserrat (1995-2003): What happens when pyroclastic flows enter the ocean?[END_REF]. Sharp surfaces represent sedimentation events [START_REF] Reading | Sedimentary environments: Processes, facies and stratigraphy[END_REF] and coincide with the abrupt transition from carbonate to volcaniclastic sedimentation, dominated by hyaloclastites of facies Hy1, with minor if any evidence of erosion and bioturbation (Figs. 11C,12A). Such sharp non-erosional surfaces have been interpreted to reflect insufficient skeletal production of carbonate systems compared to the rates of clastic accumulation [START_REF] Schlager | Drowning unconformities on carbonate platforms[END_REF][START_REF] Wilson | Cenozoic carbonates in Southeast Asia: implications for equatorial carbonate development[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF]. Suffocation of carbonate factories by volcaniclastics was likely facilitated by the rarity of significant coral reef buildups and the predominance of slow carbonate producing biota [START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF], such as foraminifera and coralline red algae, in the St. Barths limestones.

Gradational contacts also occur and represent progressive burial of carbonate systems by volcaniclastics of facies Hy1 and Hy2 (Figs. 2C,11D,12B). They indicate that prolongation of carbonate production during volcaniclastic input was possible provided a change of benthic communities from soft muddy to gravelly-shelly substrate dwellers having the capability to escape burial such as irregular echinoids (from LfCa1 to facies Mf4; Fig. 11D). Low-to highangle cross-stratifications in the overlying volcanicastic deposits (Figs. 11D,12B) suggest that volcaniclasts were transferred, considering the proximity of volcanic centers (Fig. 1), downslope via dunes, sand waves or in avalanche flows [START_REF] Caron | Contrasted carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand[END_REF][START_REF] Dorobek | Carbonate-platform facies in volcanic-arc settings: Characteristics and controls on deposition and stratigtraphic development[END_REF][START_REF] Puga-Bernabéu | Downslopemigrating sandwaves and platform-margin clinoforms in a current-dominated, distally steepened temperate-carbonate ramp (Guadix Basin, Southern Spain)[END_REF].

Temporary halts in carbonate production and deposition

Within the studied Eocene carbonate successions burrowed surfaces, interpreted as omission surfaces, are of particular interest since some of them are associated with tuffitic layers (Figs. 9, 10B, 11H-J, 12).

Omission surfaces are emphasized by a complex network of Thalassinoides burrows reaching their maximum density beneath the surface and decreasing downwards (Figs. 2D,11I,).

Most published works relate omission surfaces to stratigraphic condensation during periods of slowed/non-deposition (e.g., [START_REF] Clari | Discontinuities in carbonate successions: identification, interpretation and classification of some Italian examples[END_REF][START_REF] Hillgärtner | Discontinuity surfaces on a shallow marine carbonate platform (Berriasian-Valanginian, France and Switzerland)[END_REF][START_REF] Christ | Characterization and interpretation of discontinuity surfaces in a Jurassic ramp setting (High Atlas, Morocco)[END_REF]. Sediments by-pass, drained siliciclastic sources, wave-and/or current-induced sediment transfer and submarine erosion are major factors considered to promote non-deposition on the sea floor.

Previous authors have tied the formation of omission surfaces to specific portions of relative sealevel cycles where the position of the sea floor relative to the wave base is considered a key parameter to the onset of omission [START_REF] Lukasik | Deepening-upward subtidal cycles, Murray Basin, South Australia[END_REF][START_REF] Christ | Characterization and interpretation of discontinuity surfaces in a Jurassic ramp setting (High Atlas, Morocco)[END_REF]. However, an alternative explanation for the genesis of omission surface can be proposed based on the assumption that starved sedimentation may also result from the interruption of in situ carbonate production below and above fair-weather wave base. Although some organisms (e.g., Bivalves and Echinoids) have the ability to extricate themselves if buried beneath sediments and others to remove fine particles from their surface [START_REF] Hinchey | Responses of estuarine benthic invertebrates to sediment burial: the importance of mobility and adaptation[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF][START_REF] Knoll | Escape burrowing of modern freshwater bivalves as a paradigm for escape behavior in the Devonian bivalve Archanodon catskillensis[END_REF], episodic volcanic eruptions delivering high amounts of volcaniclastic material including ash (Fig. 10B) will result in rapid physical burial and consequent mass-mortality of benthic communities [START_REF] Heikoop | Effects of volcanic ashfall recorded in ancient marine benthic communities: comparison of a nearshore and an offshore environment[END_REF]Tomascik et al., 1997;[START_REF] Alve | Colonization of new habitats by benthic foraminifera: a review[END_REF][START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF].

The formation of omission surfaces depends on the duration of sediment starvation, and therefore here the time span between volcanic events and the recovery of carbonate factories. Where volcaniclastics were deposited above wave base, resuspension of their finer portion is likely to result in higher turbidity and in reduced light levels, thereby delaying the reestablishment of photodependent organisms [START_REF] Hallock | Larger foraminifera: a tool for palaeoenvironmental analysis of Cenozoic depositional facies[END_REF]. In addition, the potential increase of nutrient input through chemical alteration of volcanic particles may cause eutrophication at the sea floor and prevent colonization by oligotrophic and mesotrophic communities [START_REF] Hallock | Nutrient excess and the demise of coral reefs and the demise of coral reefs and carbonate platforms[END_REF][START_REF] Allmon | Role of temperature and nutrients in extinction of turritelline gastropods: Cenozoic of the northwestern Atlantic and northeastern Pacific[END_REF]Brasier, 1995a;[START_REF] Hallock | Coral reefs, carbonate sedimentation, nutrients, and global change[END_REF][START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF]. The time frame for either full recovery of the benthic communities that existed prior to the volcanic event or the renewal of carbonate systems via a switch to different biotic assemblages is difficult to estimate from the geological record but examples in the literature point to reestablishment over decades and centuries [START_REF] Heikoop | Effects of volcanic ashfall recorded in ancient marine benthic communities: comparison of a nearshore and an offshore environment[END_REF][START_REF] Tomascik | Rapid coral colonization of a recent lava flow following a volcanic eruption, Banda Islands, Indonesia[END_REF][START_REF] Pandolfi | Mass mortality following disturbance in Holocene coral reefs from Papua New Guinea[END_REF][START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF][START_REF] Vroom | Effects of volcanic ash deposits on four functional groups of a coral reef[END_REF]. This time frame is compatible with the development of a dense burrowing network and of omission [START_REF] Dashtgard | Grain-size controls on the occurrence of bioturbation[END_REF].

Recovery and renewal of carbonate factories (Fig. 13)

Besides light conditions and nutrient levels, periods of volcanic quiescence and reduced availability of volcaniclastic material were likely the principal promoting conditions for the renewal of carbonate production. In the studied successions, mixed facies (Mf1-Mf3) followed by open marine foralgal (larger foraminifera-coralline algal facies; LfCa) and rhodalgal facies (LfRh) occur above erosional surfaces cut in sandy to gravely volcaniclastic substrates (Figs. 11F,13C). Protected lagoonal foralgal facies (dasycladalean-miliolid facies; DaMi) are found above omission surfaces capping silty-sandy substrates and above marly concretionary horizons grading from sand-sized volcaniclastics (Figs. 2C,11E,). Echinofor facies (echinoidslarger foraminifera; EcF) capped by coral carpets locally represent the initial carbonate development above gradational contacts. A review of foundering photozoan carbonate facies described in the literature shows similar colonizing biota on siliciclastic substrates (e.g., [START_REF] Hendry | Coral reef diagenesis records pore-fluid evolution and paleohydrology of a siliciclastic basin margin succession (Eocene South Pyrenean foreland basin, northeastern Spain)[END_REF][START_REF] Wilson | Cenozoic carbonates in Southeast Asia: implications for equatorial carbonate development[END_REF][START_REF] Burton | Carbonate-siliciclastic Interactions; Tertiary Examples from Spain[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF][START_REF] Reuter | Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)[END_REF][START_REF] Reuter | A Middle Miocene carbonate platform under silicivolcaniclastic sedimentation stress (Leitha Limestone, Styrian Basin, Austria) -Depositional environments, sedimentary evolution and palaeoecology[END_REF]. Rhodolith-bearing units similar to those reported here (Fig. 11F), and located above erosional unconformities cut in rocky and clastic substrates, have been interpreted as transgressive deposits sitting on surfaces of marine erosion (e.g., [START_REF] Nalin | Rhodolith-bearing limestones as transgressive marker beds: fossil and modern examples from North Island, New Zealand[END_REF]. Gradational contacts have been inferred to record a progressive decrease of siliciclastic input and subsequent colonization by carbonate producers reflected in transitional mixed facies (e.g., [START_REF] Hendry | Coral reef diagenesis records pore-fluid evolution and paleohydrology of a siliciclastic basin margin succession (Eocene South Pyrenean foreland basin, northeastern Spain)[END_REF][START_REF] Burton | Carbonate-siliciclastic Interactions; Tertiary Examples from Spain[END_REF][START_REF] Lokier | Marine biota response to clastic sediment influx: a quantitative approach[END_REF].

Characteristics of the renewal of carbonate production described here suggest that they may result from a combination of factors promoting the reduction of volcaniclastic influx (e.g., changes in sediment transport direction and volcanic quiescence) and relative sea-level changes. Marly horizons at the volcaniclastic-carbonate interface, erosional and sharp-cut surfaces (Fig. 13A-B) are compatible with marine flooding. However, deepening-upward trends in facies above these surfaces have not been observed. This discrepancy might be explained by a slow rise of relative sea-level allowing aggradation without significant change of carbonate-producing biota.

Conclusions

The main results of the present study and their broader implications for the analysis of carbonate successions in volcanically-active settings may be summarized as follows.

1 The middle Eocene limestones of St. Bartholomew Island contain marine depositional facies characteristic of inner to distal middle ramp settings affected by episodic volcanic eruptions. The variety of carbonate-producing biota (i.e., chlorozoan, chloralgal, foralgal), in terms of their dependence to light intensity and tolerance to nutrient levels, suggests that carbonate production occurred mostly in euphotic conditions across an unrimmed platform with isolated coral bioherms and shoals. Other biogenic contributors (i.e., rhodalgal, echinofor) are consistent with oligophotic conditions related to resuspended fine material after storms or fine volcaniclastics input following eruption that diminished water transparency. The St. Barths Eocene carbonates provide an example of low-latitude tropical platform where non-framework building biota were important, if not dominant, sediment contributors, compared to other Eocene carbonate deposits.

2 This study shows that the effects of volcanism on carbonate factories range from burial and prolonged termination of carbonate factories, to temporarily arrested or slowed carbonate production. When volcaniclastic inputs ceased, carbonate systems reestablished. Foundering biotic communities include euphotic chlorozoan facies, oligophotic foralgal, rhodalgal and echinofor facies mixed in various proportions with volcaniclastics.

3 The discontinuous nature of the carbonate sedimentation in relation to volcaniclastic influx is reflected in: (a) erosional and sharp sedimentary surfaces that mark pronounced facies changes; and, (b) gradational contacts. Some sedimentary surfaces and contacts located at volcaniclastic-carbonate boundaries record the renewal of carbonate production above volcaniclastic deposits, while others record either the temporary halt of carbonate production or the demise of carbonate platforms buried beneath thick volcaniclastics.

The demise of carbonate factories and their prolonged shut-down in the vicinity of active volcanoes originated in the propagation of syneruptive pyroclastic flows or in the progradation/migration of wave-reworked volcaniclastic material, eroding and burying carbonate deposits. Temporary shut-down of in situ carbonate production also occurred and was likely a result of environmental stresses caused by fine volcaniclastics, including burial, lowered light levels and eutrophication.

The recovery of carbonate factories resulted from an interruption of volcaniclastic influx at the onset of volcanic quiescence promoting the reduction of volcaniclastic influx at the locus of renewed carbonate production.

Future investigations should concentrate, in a broader regional context, on the characterization of key sedimentary surfaces and discontinuities in mixed volcaniclastic-carbonate successions of the Volcanic Arc Antillean area. Correctly interpreting the origin and significance of discontinuities in carbonates deposited adjacent to active volcanoes is important to avoid misinterpretation of other key surfaces in a cyclostratigraphic and sequence stratigraphic context. Zamagni, J., Mutti, M., Kosir, A., 2008. Evolution of shallow benthic communities during the Late Paleocene-earliest Eocene transition in the Northern Tethys (SW Slovenia). Facies 54, 25-43. 1); B) Collapse due to burial by volcanic ash (facies Tu; Table 1). Texture : 'Ms' correspond to mudstone ; 'Ws' to wackestone ; 'Ps' to packstone ; 'Gs' to grainstone ; 'Fs' to floatsone ; 'Rs' to rudstone ; 'Bs' to boudnstone ; and 'Bis' to bindstone. Taphonomy : 'l' correspond to low ; 'm' to moderate, 'h' to high degree of alteration.

Figure captions

Fig. 1 .

 1 Fig. 1. (A) Location of St. Bartholomew relative to the main geological features of the Lesser Antilles in the eastern Caribbean. (B) Simplified lithostratigraphy of the Middle Eocene of St Bartholomew showing the main volcanic and limestone units. Not to scale. (C) Map showing outcropping distribution of limestone units, key stratigraphical sections (arrowed) and inferred location of eruptive centers (based on Westerkamp and Anfreieff, 1983b).

Fig. 2 .

 2 Fig. 2. Examples of stratigraphic columns logged in the studied Eocene limestones. See Fig. 1 for locations.

Fig. 3 .

 3 Fig. 3. Paleoecological modes of the most frequent irregular echinoids found in the St.Bartholomew middle Eocene limestones (based on[START_REF] Kanazawa | Adaptation of test shape for burrowing and locomotion in spatangoid Echinoids[END_REF].

Fig. 4 .

 4 Fig. 4. Taphonomic grading system established for several skeletal categories. The scale of fragmentation features for benthic foraminifers derives from that proposed by Beavington-Penney (2004). The scale of mechanical alteration for calcareous green algae is modified from Caron (2011). The importance of test infestation follows the visual chart presented in Perry (1998).

Fig. 5 .

 5 Fig. 5. Field photographs of volcaniclastic deposits from various locations (see Fig. 1). (A, B) Coarse volcaniclastic breccia containing heterometric angular clasts, ranging in size from gravel to boulder (white arrow in A), tapering limestone clasts (black arrow in A) and coral heads (arrowed in B). es: erosional surface. Location: Anse Chauvette. (C) Superposed fining-upwards dm-to m-thick pyroclastic beds exhibiting from base (arrowed) to top an erosional surface (relief <5 cm), a conglomeratic layer grading into planar-bedded gravels and sands. Anse des Cayes (Figs. 1, 12B). (D, E) Reworked hyaloclastites. Hammer: 30 cm. Location: Anse des Flamands.(F) cm-and dm-thick tabular beds of silty to sandy lapilli tuffs with wavy bases in places.Hammer: 30 cm. Location: Pointe Lézarde.

Fig. 6 .

 6 Fig. 6. Photomicrographs illustrating dominant microfacies in the studied deposits. (A-B) mixed microfacies Mf1, packstone containing abundant miliolids (Mi)(A) and common agglutinated conicals (dictyoconids, B). (C) Microfacies Mf3, packstone/grainstone containing echinoid plates (Ec), peloids and micritized grains (Micr). (D) Microfacies Mf5 (see Table 1). (E) Microfacies facies DaMi, wackestone/packstone characterized by dasycladal algal debris (Da), miliolids (Mi) and meliobesoids (Me). (F) Example of larger benthic foraminiferal -rhodolith photozoan microfacies LfRh. (G, H) Example of photozoan microfacies LfCa, packstone containing abraded and fragmented (arrowed) amphisteginids (G) and (H) grainstone showing bioclasts of orthophragminid (Or) and echinoid (Ec). (I) Example of echinoid facies association EcF, grainstone with echinoid plate (Ec) and mollusk (M) fragments.

Fig. 7 .

 7 Fig. 7. Examples of coral reef buildups. For locations see Figure 1. (A) Meter-sized lenticular reef possibly exhibiting several growth-phases (arrows), each one being laterally correlated to

Fig. 8 .

 8 Fig. 8. Hypothetical paleoenvironmental reconstruction and depositional profile of the ramp attached to submarine volcanoes for the middle Eocene limestones of St. Bartholomew.

Fig. 9 .

 9 Fig. 9. Anse des Cayes section (Limestone unit 3 -see Fig. 1 for location and Fig. 12 for field photograph) showing the interplay between volcaniclastic and carbonate sedimentation. t. arr. : temporarily arrested.

Fig. 10 .

 10 Fig.10. Consequences of the onset of volcanic activity on inner-to middle-ramp carbonate factories. A) Demise due to burial following emplacement of coarse-grained pyroclastic deposits (facies Vbr and Hy; Table1); B) Collapse due to burial by volcanic ash (facies Tu; Table1).

Fig. 11 .

 11 Fig. 11. Detailed portions of lithologic logs (see Fig. 2) showing the vertical facies successions within the deposits associated with carbonate production breaks and renewal.

Fig. 12 .

 12 Fig. 12. Sedimentary surfaces recording interruption of carbonate production. See Figure 1 for locations. (A) Sharp contact (sc) between lagoonal facies below and sand-sized volcaniclastics above. Hammer: 30 cm. Location: Pointe Mangin. (B) Gradational contact (gc) between mixed carbonate-volcaniclastic deposits (Mf) below and cross-bedded hyaloclastites above (Hy2). The contact with the limestone unit (Lu) above is described in Figure 11E. Location: Anse des Flamands. (C, D) Burrowed omission surface (bs). Close-up view in D. Scale: 12 cm. (E)

Fig. 13 .

 13 Fig. 13. Sedimentary surfaces recording the renewal of carbonate production after prolonged interruption due to volcanic activity. See Figure 1 for locations. (A) Sharp (sc), slightly undulating, weakly burrowed surface at volcaniclastic-carbonate boundary. Location: Anse des Cayes. (B) Lateral correlative surface seen in B. (C) Erosional surface (es) with a relief up to 10 cm. From the surface, fine-grained volcaniclastic deposits below are densely bioturbated by Thalassinoides (See D). Location: Pointe Mangin. (D) Close up view of Thalassinoides burrows beneath the erosional surface in C. Scale: 12 cm. (E-F) Gradational contact (gc) from argillaceous tuffitic deposits below to well-lithified grey limestone beds above with a transitional concretionary layer in between. Close-up view in F. Scale: 20 cm. Location: Pointe Lézarde.

Table 1 .

 1 Summary of facies in middle Eocene limestone units of St. Bartholomew island.

Acknowledgments

Franciane Le Quellec and Julien Le Quellec at the Réserve Naturelle de Saint-Barthélémy (resnatbarth@wanadoo.fr) are gratefully acknowledged for providing practical and logistical support. The authors wish to thank Eric François and Pierre Soudet for taxonomic identification of echinoid fossils. Were are grateful to Sedimentary Geology associate editor and to an anonymous reviewer for their contribution towards improving this manuscript.