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The Voirons Flysch (Caron in Eclogae Geologicae Helvetiae 69:297–308, 1976), is a flysch sequence aggregated into the sedimentary accretionary prism of the Chablais and Swiss Prealps. Its palaeogeographic location is still debated (South Piemont or Valais realm). We herein present a stratigraphic revision of the westernmost unit of the former Gurnigel Nappe sensu Caron (Eclogae Geologicae Helvetiae 69:297–308, 1976): the Voirons Flysch. This flysch is subdivided into three lithostratigraphic units at the formation level (the Voirons Sandstone, the Vouan Conglomerate, the Boëge Marl), with an additional unit (Bruant Sandstone) of uncertain attribution, ranging from the early Eocene to probably the late Eocene. We further propose a new model of the depositional setting of the deep-sea of the Voirons Flysch based on palaeocurrent directions, the overall geometry and sedimentary features. This model depicts an eastward deflected deep-sea fan. The stratigraphic record of the proximal part of this fan is fairly complete in the Voirons area, whereas its most distal part is only represented by one small exposure of thinly bedded sandstones in the Fenalet quarry. The stratigraphic evolution of the Voirons Flysch shows two major disruptions of the detrital sedimentation at the transition between Voirons Sandstone—Vouan Conglomerate and Vouan Conglomerate—Boëge Marl. The cause of these disturbances has to be constrained in the framework of the palaeogeographic location of the Voirons Flysch.

Grain-size control is frequently invoked to explain the compositional variation of detrital sediments in fluvial sediments. A similar possibility is here investigated in the fossil deep-sea gravity-flow deposits from the Voirons Flysch (Voirons-Wagital complex, Chablais Prealps). About 270 samples of diverse depositional settings were analysed using the framework composition, including cement and porosity, Mutti facies and grain-size measurements. Six lithofacies have been identified from cluster analysis. They correspond to channel (L1 to L3) and lobe (L4 and L5) depositional settings and to reworked turbidites (L6). Our results emphasize the close relationship between petrography and grain-size which alters the detrital signal from extrabasinal sources. The abundant polycrystalline component of proximal deposits is progressively removed while skeletal grains and additional intrabasinal grains become more abundant in distal deposits. Alongside, porosity is reduced by the simultaneous increase of cement which constrains subsequent diagenetic modifications. Hence, proximal depositional settings keep most of the inherited signal from extrabasinal sources whereas distal deposits will be homogenised. When plotted in provenance-analysis diagrams, the successive depositional settings show distinct fields possibly corresponding to different tectonic settings of the Dickinson model. This compositional variation thus creates a bias in provenance interpretation resulting from both grain-size control and flow mechanisms. Finally, our results emphasize that petrographic data must be handled with care in provenance analyses, especially when comparing various deep-sea gravity flow systems with different grain-size ranges.

We describe in detail a unique succession of Lower Pleistocene shallow-water carbonates exposed at the Misery Point sea cliff along the northern shoreline of Mayaguana Island (SE Bahamas). This km-scale outcrop comprises a record of seven past sea-level highstands that occurred between ca. 1.3 Ma and 125 ka ago, and reached relative elevations from 3 to possibly 14 m above modern sea level. Considering the tectonic stability of the Mayaguana platform in the Quaternary, the amplitudes of the recorded events could be fairly close to the corresponding glacio-eustatic changes, and thus provide calibration points for sea-level proxies derived from the deep-sea oxygen-isotope records and ice-sheet models. Moreover, our study traces the evolution of the Mayaguana bank over the past 1.3 million years, provides some insight on the birth of possibly the first island of the Bahamas archipelago, and emphasizes that the shift from bioclastic to oolitic-peloidal carbonates (i.e. the transition from the pre-Lucayan to the Lucayan limestones) occurred much later on this platform than on the northern Bahamian banks, which raises questions about the origin of this transition.

The Chablais Prealps (Haute-Savoie, France) represent a well-preserved accretionary wedge of the Western Alpine Tethys. They comprise a stack of sedimentary nappes related to palaeogeographic realms ranging from the Ultrahelvetic to the Southern Penninic. The provenance analysis is based on the Gazzi- Dickinson method and on QEMSCAN® for heavy- minerals. The Quartzose petrofacies is the most important of the two sources, and supplied three of the four formations of the Voirons Flysch. It is similar to the sources that fed the other flyschs from the Gurnigel nappe. It is characterised by a mature, quartz-rich assemblage and a heavy-mineral population dominated by apatite and the zircon–tourmaline– rutile mineral group. These observations suggest a Clastic wedge provenance. The Feldspathic petrofacies is derived from a feldspar-rich source associated with metamorphic clasts and a heavy-mineral population dominated by garnet. This provenance characterises only one formation of the Voirons Flysch, and is related to the axial belt provenance. This provenance analysis shows that the Middle Eocene to Early Oligocene Voirons Flysch was fed by two sources, in contrast to the other flyschs of the Gurnigel nappe, and further suggests that this flysch was not deposited in the Piemont Ocean but in the Valais domain. Based on the results and comparative provenance analysis with the other flyschs of the Gurnigel nappe, we propose a generic feeding model which involves the Sesia– Dent Blanche nappe, the sedimentary nappes incorporated in the accretionary prism, and probably the Briançonnais basement.

A regional sequence-stratigraphic framework is proposed for the Berriasian-Barremian shallow platform succession in the Zagros Fold-Thrust Belt (FTB), based on outcrop sections, in combination with subsurface data. The time framework is supported by new biostratigraphic results, using benthic foraminifera, dasycladalean algae and tintinnids, calibrated by Sr-isotope data. We identified and described four large-scale sequences and sixteen small-scale sequences throughout the studied succession. Large-scale sequences occur in the Berriasian-earliest Valanginian, Valanginian, Hauterivian and early to late Barremian. Based on facies associations, a relative water depth has been assigned to distinct depositional environments. Four successive architectures were observed in the platform growth: rimmed platform during the early-middle Berriasian, isolated rimmed platform in the middle Berriasian-earliest Valanginian, non-rimmed open platform to ramp in the Valanginian, and finally a mixed siliciclastic-carbonate platform to ramp in the Hauterivian-Barremian.

Since its first use in the late 80’s, the term chevron has been employed in numerous studies to describe large U- and V-shaped ridges found in or near shorelines worldwide. Most studies have so far focused on Bahamian chevrons that are exclusively of Late Pleistocene age, and on the supposed Holocene chevrons found in S-Madagascar and Australia. In the Bahamas, these deposits have been interpreted as the product of extreme storms at the end of the last interglacial (LIG) warm period. In contrast, the extensive chevrons complex exposed in S-Madagascar and on the western coast of Australia have been associated with a tsunami induced by a meteorite impact. Finally, several authors have also proposed a non-catastrophic (i.e. eolian) origin based on the recognized importance of wind-related processes in these coastal areas, and term such deposits parabolic dunes. In this paper, we collect and synthesize existing data on the morphology, sedimentology and age of these chevrons, and review the different interpretations proposed in the literature with the aim to lay out a consistent database to assist further investigations on these important coastal morphologies. In addition, we generated a synthesis of wind data at the three study areas, which highlights the relationship between present wind regimes and chevrons morphologies. The ubiquity of chevrons (likely actually parabolic dunes) in coastal areas around the globe and their relationship with coastal processes makes them crucial archives for reconstructing past wind regimes.

The ages obtained from planktonic foraminiferal assemblages retrieved from two exposures in the Gurnigel Flysch and from the re-examination of similar material gathered by previous researchers from the Voirons Flysch reveal only minor discrepancies with previous studies based on nannofossil biostratigraphy. In contrast, major divergences between this work and previous studies on the Voirons Flysch also based on planktonic foraminifera have been identified. They are generally related to distinct approaches in species classification and the use of different zonal schemes. Based on our data, the age of the Voirons Flysch extends from the Early Eocene (planktonic foraminiferal zone P7) to the Middle Eocene (planktonic foraminiferal zone P12). Contrasting with claims made in earlier studies, no specimen of Late Eocene or Early Oligocene age has been observed in the revised material. However, we cannot exclude a younger age (possibly Late Eocene) for the upper portion of this flysch from which we did not revise any sample. Thus, more research and sampling are needed to resolve this question. The palaeogeographic origin of the Voirons-Wägital complex as well as the sedimentation history of these flyschs need now to be re-evaluated in light of this revised biostratigraphic data.

New high-quality high-resolution seismic data along the western slope of the Great Bahama Bank reveals a present-day channel–levee complex developed in a pure carbonate setting. This complex grew over two buried complexes separated by erosion surfaces, suggesting both the continuity of downslope gravity-driven processes along this carbonate slope, and channel migration through avulsion, processes similar to what happens along siliciclastic slopes. Complex morphology and geometry are similar to analogs described in siliciclastic systems, but the size of the presented carbonate complex is smaller by a factor of ten. Integrating high-resolution seismic and core studies shows that this complex was built by the stacking of gravity-flow deposits, including turbidites. It presently is inactive and buried by deposits from hemipelagic fallout or low-energy density processes channeled by the gully network; Recent sediments are reworked by along-slope bottom currents dominated by internal tides. The discovery of these channel–levee complexes has implications both on the conceptual models describing the behavior of carbonate slope systems and on hydrocarbon exploration by enhancing the reservoir-bearing potential of carbonate slopes.

Early Cretaceous shallow carbonate deposits in the Zagros fold-thrust belt, SW Iran, are being studied for a high-resolution stratigraphic pattern and detailed environmental analysis. These carbonates contain diversified assemblages of dasycladalean algae, indicating shallow subtidal depositional environments. A new dasycladalean alga and interesting marker is described as Mizzia zagarthica sp. nov. from Late Berriasian–Early Valanginian deposits of the Fahliyan Formation. Focusing on the presence of reproductive organs (cysts) in the laterals, the genus, which so far has been reported only from the Permian, is emended. Based on newly described material from Greece and New Mexico, the genus Mizzia is re-assessed. The paper also includes a critical revision of the genera Neomizzia and Banciloporella.

New biostratigraphic, sedimentological and petrographic data and a thorough review of existing literature modify existing knowledge on the age, the sedimentology, the petrography and the palaeogeographic origin of the Gurnigel flysch from the Voirons massif (Haute Savoie, France). Planktonic foraminiferal biostratigraphy assigns the flysch to the upper Middle Eocene (zones P12 to P14) through to Lower Oligocene (zones P16 to P20) stages. This result contrasts with previous work, which assigned the unit to the Lower Palaeocene to upper Middle Eocene on the basis of calcareous nannofossil and dinoflagellate assemblages. The following findings suggest that the Voirons massif comprises several stacked flysch units that do not have exactly the same palaeogeographic origin: (i) the occurrence of flysch exposures in reverse stratigraphic order combined with the lack of evidence for bed overturning; (ii) the variability of palaeo‐depositional settings inferred from different flysch outcrops of similar age; (iii) the differences in the heavy mineral content; and (iv) the anomalous superimposition of distal turbidites and/or basinal contourites (Saxel Marls) over proximal turbidites (Vouan Conglomerates). The young age of these kilometre‐sized flysch slices precludes their hitherto postulated locus of deposition in the South‐Penninic Ocean, and rather indicates a provenance from the Ultrahelvetic and/or North‐Penninic (Valais) palaeogeographical domains. Finally, none of the nannofossil assemblages are contemporaneous with the observed planktonic foraminifera associations, suggesting that they have been reworked, dissolved, or just simply diluted and not found by earlier researchers. This study from the Voirons massif shows that planktonic foraminifera associations are a highly reliable biostratigraphic tool for obtaining accurate ages of flysch successions.

New high-quality multibeam and seismic data image the western slope of the Great Bahama Bank and the adjacent floor of the Straits of Florida. The extensive survey reveals several unexpected large- and small-scale morphologies. These include bypass areas, channel-leveelobe systems, gullied slopes, and products of slope instabilities at various scales, including long slump scars at the lower slope and mass transport complexes that extend ~30 km into the adjacent basin floor. The toe of the slope is irregularly covered with deep-water carbonate mounds. The abundance of the individual morphological features varies from north to south. From 26°00'N to 25°20'N, the slope is dissected by numerous deep canyons that abruptly end southward, where the slope is characterized by a smooth lower portion and small regularly spaced furrows in its upper part. Further south, two long (25-50 km) scars document instability at the lower slope. One of these scars is the source area of a large mass transport complex. In addition to this large-scale feature, several types of gravity-induced sedimentary processes are revealed. Most of the morphologies and inferred processes of this carbonate system are similar to those observed in siliciclastic systems, including mass transport complexes, gravity currents initiated by density cascading, and overspilling channeled turbidity currents. For the first time, a clear asymmetric channel-levee system has been identified along the slope, suggesting similitude in sorting processes between carbonate and siliciclastic systems and enhancing the reservoir-bearing potential of carbonate slopes. Notable differences with siliciclastic systems include: the lack of connection with the shallow and emerged part of the system (i.e., bank top), and the small size of the sedimentary system. © 2012 Geological Society of America.

A complex interplay of environmental factors may affect regionally important Cenozoic carbonate deposits, and a combination of different controls may result in comparable deposits. There is, therefore, a need for purely descriptive nomenclature to define regionally extensive groupings of carbonate deposits. This terminology is reviewed here. In addition to the well-established chlorozoan (or coralgal), chloralgal, foramol, rhodalgal,molechfor and bryomol definitions, two new terms, LB-foralgal and thermacor,are proposed. These purely descriptive groupings allow for good spatial and temporal subdivision of Cenozoic carbonate deposits. The continued use of objective terms for Cenozoic carbonate deposits does not preclude the use of other interpretative grain association terminology, and a two-tier system might be adopted. However, it should be clearly stated when groupings based on benthic components are being used purely descriptively, and therefore in an objective sense. It is hoped that this descriptive approach to regionally important deposits will help to promote objective discussions about controls on carbonate sedimentation and environmental change during the Cenozoic.

Detailed sequence and facies analyses of eleven stratigraphic sections, positioned on two platform to basin transects, on the Ragusa ramp (Sicily, Italy) demonstrates that two facies models must be used to describe the internal architecture of this carbonate edifice near the Serravallian/Tortonian boundary. Seven facies zones, based on the paleobathymetric position of the carbonate-producing biota, have been defined and described for each of these stages. During the late Serravallian, the inner ramp was characterized mainly by small epiphytic biota of the foramol association, whereas the middle ramp was dominated by rhodoliths and minor benthic foraminifera, bryozoans, barnacles, serpulids and echinoids. In contrast, during the early Tortonian, the inner ramp was characterized by a chlorozoan biota (Porites, Halimeda), and the middle ramp by branching Corallinacea and rhodoliths. This seemingly minor modification in the type and locus of carbonate production, and the associated changes in hydrodynamism, had profound consequences on the overall geometry of the platform which evolved from a distally steepened ramp, in the late Serravallian, to a geometry approaching that of flat-topped platform in the early Tortonian.

The alternation of carbonate deposits and paleosols compose the emerged part of the Bermuda archipelago. The pedological units present a complex and diversified mineralogy. Former studies demonstrated that the paleosols are not primarily a product of the unique dissolution of the surrounding carbonates, but contain a massive input of allochthonous non-carbonate detrital material. Researchers during more than the past three decades have attributed this flux of insoluble residues (IR) to Saharan dusts. We carried out systematic field and mineralogical analyses on the Quaternary paleosols from the Bermuda archipelago. Their mineralogical assemblage predominantly includes carbonates, clay minerals (kaolinite, chlorite and chlorite/vermiculite), phosphates, and aluminium and iron oxides/hydroxides. This assemblage is strikingly close to the mineralogy of the weathered volcanic substrate of Bermuda, but noticeably different from the mineralogy of Saharan dust. Moreover, we found volcanic lithoclasts in numerous paleosol profiles all over the archipelago and in all the recorded time intervals. We thus consider the volcanic seamount underlying Bermuda as the main source of non-carbonate minerals detected in the paleosols. This hypothesis further resolves the anomalous maturity of Bermudan paleosols compared to their southern counterparts in the Bahamas and Barbados.

We respond to Hearty et al.'s objections to our interpretation of upper Pleistocene coastal landforms from Bermuda and the Bahamas as aeolian dunes rather than wave-induced deposits. Their remarks concern the origin of fine-scale laminae and fenestral pores observed in these landforms, the apparent lack of steeply dipping foresets, the inference that carbonate coastal dunes can migrate, the vicinity of wave-deposited boulders that we did not mention, and finally, the palaeoclimatic reconstruction we derived from our interpretation. Although, we do not exclude—and never did—that occasional storm-generated waves washed up and over these dunes and created some scours, we maintain that these controversial deposits have an aeolian origin.

Piles of carbonate sand dredged onto Stocking Island (Exuma Chain, Bahamas) during World War II are now relatively well-lithified down to a depth of about 80 cm and may contain up to 8% of interstitial calcite cement, a volume comparable to that measured from 1000-yr-old beach ridges elsewhere in the Bahamas. Rates of meteoric diagenetic changes are thus more rapid than previously assessed in this area (∼600 cm3 of calcite cement produced by m3 of rock per year). Preservation of hydrodynamic sedimentary structures, footprints, and the lack of aeolian bedforms (e.g. dunes, ripples) on the surface of these sediments further show they have not been reworked by the wind at all. Therefore, the carbonate aeolianites of Holocene and Pleistocene ages forming the bulk of the islands of Bermuda and the Bahamas were likely deposited during relatively dry periods when the effects of meteoric diagenesis were limited. Reduced moisture, along with sediment availability and wind energy, appears as a key player in carbonate aeolianite genesis.

The late Pleistocene stratigraphic record from the Bahamas and Bermuda archipelagoes includes peculiar V-shaped coastal ridges and wedges of seaward-dipping planar beds showing fenestral porosity up to 40 m above present sea level. Judging from this porosity, these landforms were till now interpreted as resulting from the action of giant waves during a period of climatic instability at the end of the last interglacial period. The occurrence of widespread mm-thick laminae of aeolian origin (subcritically climbing translatent stratification) throughout these deposits does not agree with this hypothesis. It rather suggests that the V-shaped ridges and seaward-dipping beds represent fossil parabolic and climbing aeolian dunes, respectively. The occurrence of fenestrae high above the intertidal zone could be related to both wave splashing and rainfall action. Parabolic dunes are restricted to the NW Bahamas. They were probably formed during a time interval (ca. 500–5000 yr), when regional climatic conditions were dryer than today, and characterized by persistently blowing NE trade winds.

Sedimentological, petrographic and geochronological (uranium series and amino acid racemization dating) study of middle Pleistocene deposits from the archipelagos of Bermuda and The Bahamas revealed the occurrence of marine terraces of possible stage 11 age at +2, +7 and over 20 m above mean sea level. Considering the tectonic stability of the investigated regions, these elevated deposits likely correspond to three discrete, higher than present sea levels during this time period, which is regarded by many as the warmest interglacial of the late Quaternary. It follows that warmer than present climatic conditions might profoundly modify water distribution between the cryosphere and the oceans. The punctuated nature of our stratigraphy further suggests that future deglaciation might not be a smooth process, but could be marked by rapid ice-sheet breakdown leading to abrupt, meter-scale sea-level rises. Given the long period of warm climate and stable sea level of the past few thousands of years and CO2 loading of the atmosphere, the probability of a rapid eustatic rise must be seriously considered.

Detailed petrographic and sedimentological analysis of Tyrrhenian coastal deposits from four sites in Sardinia provides new data about climate and sea-level changes during the early part of the last interglacial (isotopic substage 5e) and shows that facies analysis is not only useful for the identification of ancient depositional environments, but also represents a powerful tool for evaluating past climatic conditions and sea-level forcing mechanisms. Two shallowing-upward sequences (sensu Ward, W.C., Brady, M.J., 1979. Strandline sedimentation of carbonate grainstones, Upper Pleistocene, Yucatan Peninsula, Mexico. Am. Assoc. Pet. Geol. Bull. 63, 362–369), commonly separated by an erosion surface and displaying complex geometric relationships, occur above modern sea level at several locations along the shorelines of Sardinia. These sequences include upper shoreface to backshore deposits and were formed during separate sea-level highstands attributed to isotopic substage 5e. Our recent revision of these deposits indicates that each sequence presents distinctive petrographic characteristics. The older succession essentially contains mixed calcarenites, rich in quartz grains and lithic fragments, whereas the younger sediments are dominated by carbonate bioclasts such as red algae, coral and mollusk fragments. Both units apparently accumulated in a similar depositional setting, but during different climatic regimes. The petrography of the lower unit reflects a temperate-humid period characterized by increased weathering and continental erosion, whereas the composition of the upper one suggests a dryer, and possibly warmer, climate favoring active carbonate production. The disparity in petrographic composition between sequences probably records the migration of atmospheric circulation cells, i.e. a shift of climate belts, before and after the ∼128-ka insolation maximum. Our climatic data are coherent with the calculated insolation curves for isotopic substage 5e and thus support the Milankovitch hypothesis for the origin of Pleistocene climates. In contrast, our sedimentological data clearly show the occurrence of two distinctive highstands of sea level during this time period, which does not agree with the hypothesis. It follows that the relation between orbitally induced insolation variations, climate and sea level is not necessarily straightforward.

Coeval stratigraphic units of similar petrology occur throughout the northern Bahamas islands. The petrographic composition of these limestones provides clues about regional sea level and climate changes during the late Quaternary. At least eight fossil shoreline units, which are linked to transgressive episodes between the middle Pleistocene and the late Holocene, are recognized in the Bahamas. The petrographic composition of these units is either dominated by ooids and peloids or by bioclasts. Sedimentological observations demonstrate that oolitic‐peloidal units were formed when sea level was higher than today, whereas skeletal units were deposited at or below modern ordnance datum. Skeletal units may reflect times of partial, or modest platform flooding, when the bulk of sediments brought to islands originates from bank-margin reefs. In contrast, oolitic‐peloidal units correspond to major flooding events and active water circulation on the bank top. Cement fabrics further show that the early diagenesis of oolitic units took place during warm and humid climatic conditions, whereas skeletal rock bodies underwent subaerial diagenesis during drier climatic conditions characterized by marked seasonal changes. This example from the Bahamas suggests that compositional analysis of limestone from fossil carbonate platforms could be used for resolving ancient climate and sea-level changes.

Iranella inopinata gen. and sp. nov. was first described in the unpublished thesis of Gollestaneh (1965), as an incertae sedis from the Lower Cretaceous carbonate rocks of the Zagros fold-thrust belt. More recently, the taxon was formally, although provisionally described by Hosseini and Conrad (Geol Croat 61:215–237, 2008), as a dasycladalean alga named Salpingoporella? inopinata. Here, based on the interpretation of quite-abundant although scattered fragments, it is assigned to Iranella, a large-sized, stalked, and capitulum-shaped new genus of Dasycladales. The lower, stalked part of the thallus is cylindrical, strongly calcified, with first-order laterals only, while the large capitulum is only partly calcified, showing one or two orders of laterals. Traces of cysts (reproductive organs) are present in the basal stalk, either in the stipe or the laterals. Iranella inopinata looks to be endemic to the southwestern part of the Tethyan realm, in the Zagros area and also south of the Persian Gulf. In the Zagros Mts., it extends from the Berriasian to the Aptian, with an Acme Zone in the Valanginian. Sequential interpretation proves the presence of this species in the late transgressive and early highstand stages of system tracts, and reveals a low-energy, restricted, lagoonal or back-reef depositional environment, in an inner-platform setting.

The present study provides new insight into the Quaternary stratigraphy of the Bahamas. Refining the stratigraphic record of tectonically stable carbonate islands, such as the Bahamas, is important for improving our perception of eustatic and climatic variations during this time interval. Two key-sections located 15 km apart in the northern portion of Eleuthera display three vertically stacked rock-units: (1) a basal unit consisting of up to four eolianites separated by paleosols, (2) intermediate oolitic deposits showing beach facies at +6 m, and (3) an upper bioclastic eolianite overlain by a thick calcrete. The occurrence of beach facies at an elevation of 6 m above MSL suggests an Early Sangamonian age (isotopic substage 5e) for the intermediate oolitic deposits. Because of its position below a thick calcrete, the upper unit was more likely formed during a later highstand of the Sangamonian (substage 5c or 5a), rather than during the Holocene. It follows that the basal unit clearly predates the last interglacial. This new evidence from Eleuthera shows that pre-Sangamonian rocks may be more extensive in the Bahamas Archipelago than previously thought. It also emphasizes the widespread occurrence of bioclastic limestones in an area often considered as being entirely composed of oolites.

New high-quality multibeam data presented here depict the northern slope of the Little Bahama Bank (Bahamas). The survey reveals the details of large- and small-scale morphologies that look like siliciclastic systems at a smaller scale, including large-scale slope failure scars and canyon morphologies, previously interpreted as gullies and creep lobes. The slope exhibits mature turbidite systems built by mass-flow events and turbidity currents. The sediment transport processes are probably more complex than expected. Slope failures show sinuous head scarps with various sizes, and most of the scars are filled with recent sediment. Canyons have amphitheater-shaped heads resulting from coalescing slump scars, and are floored by terraces that are interpreted as slump deposits. Canyons rapidly open on a short channel and a depositional fan-shaped lobe. The entire system extends for ∼40 km. The development of these small turbidite systems, similar to siliciclastic systems, is due to the lack of cementation related to alongshore current energy forcing the transport of fine particles and flow differentiation. Detailed analyses of bathymetric data show that the canyon and failurescar morphology and geometry vary following a west-east trend along the bank slope. The changing parameters are canyon length and width, depth of incision, and canyon and channel sinuosity. Accordingly, failure scars are larger and deeper eastward. These observations are consistent with a westward tectonic tilt of the bank during the Cenozoic. © 2012 Geological Society of America.

Sedimentological and petrographic study of Holocene deposits in the Eastern Bahamas shows that sedimentation occurred episodically during this period of continually rising sea-level. The Holocene stratigraphic record exposed on the islands of San Salvador, Lee Stocking and Cat consists of two distinctive units separated by a paleosol: (1) 5000 year-old oolitic eolianites deposited when sea-level was lower than today, and (2) 3000 to 500 year-old bioclastic paleo-beaches and dunes that are congruent with the present stand of sea-level. A five-stage model that reconciles intermittent sedimentation pattern with continuous sea-level rise is presented. Pre-Holocene topography and changes in the rate of the transgression seem to regulate local 4 hydrodynamic conditions, which in turn control onset and offset of sedimentary processes. This Holocene example of episodic sedimentation during an uninterrupted transgression should be considered when studying ancient discontinuities that are systematically interpreted in terms of relative sea-level fall.

The origin of the ooids forming the bulk of many large Pleistocene and Holocene ridges on the windward islands of Great Bahama Bank is not well understood. A formation locus situated to the east of these islands would be consistent with present-day sediment fluxes, but outer platforms in these areas are extremely narrow today and appear unsuitable for large-scale ooid production. The four models presented hereafter suggest that ooids could originate (1) from these narrow outer platforms, (2) from wider outer platforms that no longer exist, (3) from the bank interior via tidal channels, and (4) directly from the bank interior by means of a westerly sediment flux. With the exception of option #3, all models are validated by field observations in Eleuthera and in the Exumas. Corroboration of models #2 (outer platform erosion) and # 4 (westerly flux) further indicates that past depositional environments and sedimentary processes on Great Bahama Bank could have been significantly different from those operating today.

Les dépôts littoraux du Pléistocène supérieur de Sardaigne ont été étudiés depuis le siècle dernier, mais n'ont jamais été abordés sous l'angle de la sédimentologie et de la stratigraphie séquentielle. Ce travail concerne un affleurement complexe situé sur la côte occidentale de la Sardaigne à proximité de San Giovanni di Sinis, affleurement dans lequel trois séquences de dépôts peuvent être identifiées. La séquence inférieure surmonte une surface d'érosion entaillée dans les marnes messiniennes. Un conglomérat de base recouvert par des sables à rides de courant et laminations de plage témoigne d'un environnement marin littoral. L'essentiel de cette première séquence est cependant constitué de dunes éoliennes localement pédogénisées et de colluvions. Une imposante surface d'érosion marque la limite supérieure de cette séquence. Le conglomérat de base de la deuxième séquence qui renferme des galets pédogénisés passe à des sables à laminations de plage. Ces faciès sont surmontés par une lumachelle à Mytilus et par des vases bioturbées à ostracodes qui correspondent à des dépôts lagunaires. La présence localisée de charophytes et de rhizolithes traduit l'influence d 'eaux douces et un début de pédogenèse. A nouveau, une importante surface d'émersion entaille ces dépôts. La troisième séquence débute avec des faciès de plage et d'avant-plage très riches en corallinacées et s'achève avec des dépôts éoliens qui progradent par place directement sur des dépôts d'avant-plage et des dépôts de chenal de marée. L'examen sédimentologique détaillé de cette dernière séquence suggère que les concepts de la stratigraphie séquentielle sont applicables à l'analyse de systèmes sédimentaires littoraux de dimension réduite. Les principales surfaces d'érosion se sont formées durant des phases d'abaissement important du niveau marin et correspondent à des limites de séquences. Les conglomérats pourraient représenter les dépôts de l'intervalle transgressif, tandis que les successions «bathydécroissantes» pourraient correspondre au prisme de haut niveau marin. Il est probable que les trois séquences identifiées, imputables à des variations eustatiques importantes, représentent l'enregistrement sédimentaire des trois cycles climatiques majeurs qui ont marqué le dernier interglaciaire entre 130 000 et 70 000 ans. Tyrrhenian (Upper Pleistocene) coastal deposits in Sardinia have been studied since the last century, but have never been interpreted in terms of detailed sedimentology and sequential pattern. The present paper deals with an outcrop close to San Giovanni di Sinis on the western coast of Sardinia, where three depositional sequences can be identified. The lowermost sequence overlies an erosion surface which cuts into Messinian marls. A basal conglomerate including coralline algae, and sandstones displaying current ripples and beach lamination point to a coastal-marine depositional environment. The bulk of the sequence, however, is made up of eolian dunes with interstratified paleosols, and of colluvial deposits. An erosional surface terminates this sequence. The basal conglomerate of the second sequence contains pebbles with pedogenetic features, and is overlain by beach-laminated sands. Superimposed bioturbation and an important bed of in-situ Myrilus shells suggest that the coastal-marine environment passed into a lagoonal one. Ostracods charophytes and pedogenesis indicate fresh-water influence and local emersion at the top of this sequence. Again, an erosional surface truncates the deposits. The third sequence starts with shoreface and foreshore deposits rich in coralline algae and ends with eolian facies. Locally, the eolian dunes prograde directly over shoreface and tidal-channel deposits. The major erosion surfaces probably formed during important drops of sea-level and correspond to sequence boundaries. The conglomerates are interpreted as transgressive deposits, whereas the shallowing-upward facies successions represent regressive highstand deposits. The three sequences of San Giovanni di Sinis may thus have formed during three successive sea-level fluctuations, which can tentatively be correlated with the three climatic cycles during the last interglacial, i.e. between 130,000 and 70,000 years B.P.

Significant synchronous shifts in the chemistry, mineralogy, grain sizes and color of the sediments at 6 m below sea floor (mbsf) at ODP Site 1195 on the Marion Plateau (NE Australia) are interpreted to reflect a major regional paleoceanographic change: the initiation of the southern province of the Great Barrier Reef (GBR). The onset of this massive carbonate production centre nearby resulted primarily in increased deposition of carbonate-rich sediments of neritic origin. Both sedimentation rate and terrigenous input record a coincident decline attributed to inshore trapping of materials behind the reefs. Our best estimate places the development of reef framework in the southern part of the GBR between 560 and 670 kyr B.P., based on an age model combining magnetostratigraphic and biostratigraphic data. The proposed estimation agrees with previous studies reporting an age between 500 and 930 kyr B.P., constraining more tightly their results. However, it does not support research placing the birth of the GBR in Marine Isotope Stage (MIS) 11 (∼ 400 kyr), nor the theory of a worldwide modern barrier reef development at that time.

The Mayaguana and Caicos platforms are both located in the SE Bahamas. Caicos is one large edifice supporting small islands, whereas Mayaguana is smaller and comprises one island covering most of the bank surface. Providenciales (Caicos) and Mayaguana islands predominantly consist, in different proportion, of reefal framestones and oolitic grainstones dating from the last interglacial period. Oolitic ridges are widely exposed on Providenciales, whereas reefal deposits are confined to the west coast. On this island, the older substrate consists of oolitic and bioclastic eolianites of middle Pleistocene age. On Mayaguana, oolitic ridges are subordinate to the reefs, and the oldest rock units include altered eolianites containing fragments of benthic foraminifers that became extinct in the Pliocene and fine-grained dolostone of possible middle Miocene age. This difference in the distribution of upper Pleistocene facies could be related to the extent of emerged land on platform tops or to the thickness of the water layer covering the latter during the last interglacial highstand. The oolitic and bioclastic substrates exposed on Providenciales are similar to those observed in the northern Bahamas. If confirmed, the pre-Quaternary age of the dolomitic and eolian units on Mayaguana would question some fundamentals of Bahamian geology.

International audience; We provide here new 234U/230Th ages measured on coral samples collected from a reefal terrace exposed on Great Inagua Island (Bahamas) that was, up to now, wholly attributed to the last interglacial period (Marine Isotope Stage 5e). Our results from the upper part of the terrace confirm the previously reported MIS 5e age, whereas ages obtained from the lower part range between 139,000 and 193,000 years BP, spanning most of MIS 6. Petrographic examination showed that secondary aragonite cement and internal sediment occur in the coral chambers of these samples, indicating they were rejuvenated and likely date from the penultimate interglaciation (MIS 7). The studied terrace is thus a composite build-up and its lower part represents the first coral reef of MIS 7 age ever described in the Bahamas archipelago. Our results further suggest (1) that Great Inagua Island recently underwent a phase of tilting, and (2) that sea level was close present datum during MIS 7. © 2006 Elsevier B.V. All rights reserved.

This chapter focuses on the three-dimensional mosaic making up the islands. The chapter uses the stratigraphic scheme, which differs from the formal lithostratigraphic column. It has become clear that there is variability among Bahamian islands with respect to their stratigraphic architecture, and that there are patterns to this variability. Such observations present in the chapter provide tentative classification of islands where one can find or expect to find different types of stratigraphic architecture. Although the classification is still a hypothesis, which one can test by studying more Bahamian islands, the chapter includes it as an organizer and provides a potential framework for (1) understanding Bahamian islands fully, and (2) comparing Bahamian islands to other kinds of carbonate islands. The architecture of Bahamian islands shows that they grow by lateral accretion or vertical stacking depending on their exposure to the open ocean and the width of the outer platform.

Kindler Pascal, Charollais Jean, Ujetz Bernhardt, Wernli Roland. Middle-Eocene bottom-current deposits from the Ultrahelvetic Prealps in the Haute-Savoie, France. A case of mimic recycling. In: Géologie Méditerranéenne. Tome 21, numéro 3-4, 1994. Perimediterranean carbonate platforms. First International Meeting. Marseille – France (5-8 septembre 1994) sous la direction de Jean-Pierre Masse. pp. 97-99.

Examination of several closely spaced cores from western New Providence, Bahamas, shows a classic shoaling-upward progression of facies. Refined age constraints from magnetostratigraphy indicate that since the Brunhes/Matuyama boundary (0.78 Ma), only three sea-level highstands have flooded this part of the platform. The reefal-skeletal-oolitic-peloidal facies sequence, probably representing deposition during fourth-order highstands, show lateral facies changes and perhaps regional climatic influences. This skeletal-to-nonskeletal transition is common in other Bahamian platform records, and appears to be youngest near the edges of the platform. Estimates of sea level during the reversed-polarity Matuyama, without subsidence corrections, show that it reached within about 10 m below pre ent sea level. During the Brunhes chron, at least one highstand came to within 6-7 m of present mean sea level. The uppermost part of a core, containing beach facies, is now about 6 m above sea level and is thought to represent the 0.13 Ma sea-level event.

Fenestrae are primary or penecontemporaneous pores in the sediment framework that are larger than grain-supported interstices. These features have long been used to characterize peritidal environments and as a sea-level indicator in ancient successions. We report the occurrence of irregular (i.e., equidimensional) fenestrae in Pleistocene eolianites on San Salvador and Eleuthera (Bahamas), as much as 35 m above the coeval sea level. A rainstorm-induced origin is proposed as the mechanism for production of such voids in eolian deposits. We suggest that fenestrae should be used as a sea-level indicator only when they are associated with other intertidal or peritidal characteristics.

Marine deposits at +20 ± 3 m on the tectonically stable coastlines of Bermuda and the Bahamas support the hypothesis of a partial collapse of the Antarctic ice sheet during the middle Pleistocene. Beach sediments fill a sea cave at +22 m in Bermuda, and horizontal, fenestrae-filled beds crop out on platforms at two sites as high as +21 m in Eleuthera, Bahamas. Carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment. Amino acid racemization and TIMS (thermal-ionization mass spectrometry) dates constrain the age of the deposits to between 390 and 550 ka, while proxy evidence supports a correlation with oxygen isotope stage 11. This direct geologic evidence of a 20% decrease in polar ice during the middle Pleistocene has important implications for the stability of ice sheets during warm interglaciations.