FIG 1 - uploaded by Paul Hearty
Content may be subject to copyright.
Map of the Bahama Islands. A 200-m bathymetric contour outlines shelf areas of the Bahama Banks, Florida, and Cuba. Sample sites from the Appendix are identified by island code (e.g., G, Grand Bahama; A, Abaco) and number.
Source publication
The surficial geology of the tectonically stable Bahamian archipelago preserves one of the most complete records of middle to late Quaternary sea-level-highstand cycles in the world. However, with the exception of deposits from marine isotope substage (MIS) 5e, fossil corals for radiometric dating of this rich stratigraphic sequence are rare. This...
Contexts in source publication
Context 1
... mobile sedimentary blanket on the flat-topped Bahama Platform ( Fig. 1) is a sensitive monitor of sea-level fluctua- tions. Waves and wind, driven by powerful storms, remold the sediments into beach, dune, and washover ridges, which upon subaerial exposure are "frozen" in place by rapid cementation. Carbonate sedimentation occurs during broad interglacial high- stands while the platform is partially or ...
Context 2
... the past decade, more than 500 sites in Grand Bahama, Abaco, Andros, New Providence, Eleuthera, Cat, Exumas, San Salvador, Long, Acklins, Mayaguana, Caicos, and Great In- agua islands (Fig. 1) were investigated. Previous studies have examined the stratigraphy and carbonate petrography of many of these sites (e.g., Kindler and Hearty, 1996), from which it was determined that sea-level modulation of sediment forma- tion has similarly and simultaneously affected all the islands, resulting in a collection of either oolitic or ...
Context 3
... eolianites are superimposed on the partially calci- tized "old oolites" and underlie the distinctive aragonitic oolite of the last interglaciation. In most cases across the Bahamas, only eolian facies are observed (e.g., Fig. 2, section 13), but in New Providence Island, beach fenestrae indicate that sea level was at or near the modern datum during a late middle Pleis- tocene interglacial highstand ). These deposits lie seaward of the higher, older oolitic ridge associated with the 300,000-yr U-series age mentioned previ- ously and underlie the last interglacial oolite of ...
Context 4
... intervals of emergence and nondeposition (i.e., limestone-soil couplets). Mean A/I values per lithostrati- graphic unit per island group show that equivalent units on different islands produce equivalent ratios (Table 1; Fig. 3). Given the stratigraphic sequence, the aminozones reflect cor- responding, distinct ages. ...
Citations
... Many geochronological investigations have examined the age and origin of calcareous coastal dune successions (eolianites) to resolve their formation in relation to Quaternary sea-level changes (Brooke, 2001). In a global context, major tracts of eolianites are generally linked to interglacial or interstadial high sea levels, as documented in coastal regions of South Africa and Mozambique (Armitage et al., 2006;Bateman et al., 2011), The Bahamas (Hearty and Kaufman, 2000), and Western and southern Australia (Murray-Wallace et al., 2001;Blakemore et al., 2015;Lipar et al., 2017). The increased accommodation space of shallow marine sedimentary carbonate environments during interglacial sea levels is thought to have enhanced the production of bioclastic, skeletal particles, which were subsequently entrained landward by wave processes and onshore winds to nourish coastal dunes (Brooke, 2001;Murray-Wallace, 2018). ...
... The French Bay Member is composed of a reasonably well-preserved oolite exhibiting a range of environments from subtidal to intertidal to eolian (Carew and Mylroie, 1985;Caputo, 1995;Kindler and Hine, 2008). The French Bay Member has been attributed to MIS-5e-based amino acid racemization data (Hearty and Kaufman, 2000). This lower member has been interpreted as representing a transgressive eolianite (Hearty and Kindler, 1993;Kindler and Hearty, 1996;Hearty and Kaufman, 2000). ...
... The French Bay Member has been attributed to MIS-5e-based amino acid racemization data (Hearty and Kaufman, 2000). This lower member has been interpreted as representing a transgressive eolianite (Hearty and Kindler, 1993;Kindler and Hearty, 1996;Hearty and Kaufman, 2000). The Cockburn Town Member mainly comprises coral reef boundstone or rudstone and shell-rich floatstone representing subtidal lagoonal and reef settings. ...
... The Cockburn Town member has been described as containing a prominent unconformity separating two reef units. This twophase depositional model during MIS 5e is also supported by distinct ages within the MIS 5e stratigraphy from amino acid racemization data and U-series data (Hearty and Kaufman, 2000;Chen et al., 1991;Thompson et al., 2011;Skrivanek et al., 2018). At some localities, such as the type section at Grotto Beach on San Salvador Island, a shallowing-upwards sequence is observed from subtidal reef and lagoonal facies to subaerial oolitic calcarenites. ...
This paper provides a summary of published sea-level archives representing the past position of sea level during the Last Interglacial sea-level highstand in the Bahamas, Turks and Caicos, and the eastern (Atlantic) coast of Florida, USA. These data were assembled as part of a community effort to build the World Atlas of Last Interglacial Shorelines (WALIS) database. Shallow marine deposits from this sea-level highstand are widespread across the region and are dominated by carbonate sedimentary features. In addition to depositional (constructional) sedimentary indicators of past sea-level position, there is also evidence of erosion, dissolution, and/or subaerial exposure in places that can place an upper limit on the position of sea level. The sea-level indicators that have been observed within this region and attributed to Marine Isotope Stage (MIS) 5e include corals, oolites, and other coastal sedimentary features. Here we compile a total of 50 relative sea-level indicators including 36 in the Bahamas, three in West Caicos, and a remaining 10 for the eastern seaboard of Florida. We have also compiled U-Th age data for 24 fossil corals and 56 oolite samples. While some of these archives have been dated using U-Th disequilibrium methods, amino acid racemization, or optically stimulated luminescence, other features have more uncertain ages that have been deduced in the context of regional mapping and stratigraphy. Sedimentary archives in this region that constrain the elevation of the past position of sea level are associated with uncertainties that range from a couple of decimeters to several meters. Across the Bahamas and on West Caicos, one of the observations that emerges from this compilation is that estimation of sea-level position in this region during Marine Isotope Stage 5e is complicated by widespread stratigraphic evidence for at least one sea-level oscillation. This evidence is defined by submarine features separated by erosion and subaerial exposure, meaning that there were likely multiple distinct peaks in sea level rather than just one. To this end, the timing of these individual sea-level indicators becomes important when compiling and comparing data across the region given that different archives may have formed during different sub-orbital peaks in sea level. The database can be found at https://doi.org/10.5281/zenodo.5596898 (Dutton et al., 2021).
... The von Mises probability density function indicates that dunes of the Tamala Limestone were migrating ENE. significantly lower A/I ratios, only the 250-850 μm fraction of the sieved samples was kept so that to exclude fine intergranular cements (Hearty and Kaufman, 2000). Potential contamination by remaining cement was reduced through a bleaching of 30% of their total mass with 2 M HCL. ...
... Lower A/I ratios indicate younger units but the reliability of the measurements is highly dependent of the amino-acid concentration within the carbonate. It is already known that amino acid concentration decreases with the age of the sample and the state of diagenesis (Hearty and Kaufman, 2000;Hearty and O'Leary, 2008;Roof, 1997), so this observation either indicates that carbonate units tend to be older or that the degree of carbonate diagenesis increases towards the East. Previous studies that have been conducted in the Perth Basin have demonstrated that the yellow sand overlying the Tamala Limestone formed by residual accumulation of the siliciclastic material after the dissolution of the carbonate units (Bastian, 2010(Bastian, , 1996(Bastian, , 1994Newsome, 2000;Playford et al., 2013). ...
The carbonate units grouped under the name “Tamala Limestone” outcrop for a thousand kilometres along the coast of Western Australia. The extensive Zuytdorp Cliffs shaping the northern half of the coastline up to Shark Bay expose and offer an exceptional access to the stratigraphy of this formation.
The regional survey of the Shark Bay region, which combines both stratigraphic and sedimentological analyses, reveals that the Tamala Limestone is a dry accumulating aeolian system composed of large transverse dunes migrating parallel to the prevailing winds. Accordingly, the amino acid-data show an aging of the units towards the east. Episodes of carbonate aeolian sedimentation correlate with the successive glacial intervals of the Pleistocene whilst paleosols are correlated with breaks in the sedimentation during interglacial intervals.
Palaeoclimate reconstructions reveal that sea level and sea surface temperature of the Indo-Pacific Warm Pool were lower during glacial intervals. The weakened Leeuwin Current, which flows along the western coast of Australia and is the main source of precipitation, contributed to the aridification of the region. Consequently, and associated with a northward migration of the Hadley and Ferrel cells, periods of glaciation were drier. By contrast, paleosols developed through dissolution of the carbonate units during more humid interglacial intervals.
... Reconstructing the history of climate and sea-level changes during the Quaternary is of prime importance for better addressing potential anthropogenic climate changes. To unravel this history, we investigate the record of shallow-water tropical carbonates because of their sensitivity to subtle environmental fluctuations (e.g., Lees and Buller, 1972;Mutti and Hallock, 2003;James and Jones, 2015 and references therein), their ability to preserve past sea-level indicators due to rapid cementation (Dravis, 1996;Friedman, 1998;Kindler and Mazzolini, 2001), and their accessibility to multiple dating methods (e.g., Hearty and Kaufman, 2000;Thompson et al., 2011). Further, peritidal limestones from tectonically quiescent areas, such as the Bahamas, are particularly suitable for assessing ancient sea-level markers because the elevation uncertainties related to subsidence or uplift rates are minimal at these locations. ...
... Around that time, three allostratigraphic units were defined by Carew and Mylroie (1985) on San Salvador: the Owl's Hole, the Grotto Beach, and the Rice Bay formations (Table 1). Carew and Mylroie's (1985) stratigraphic scheme was largely maintained by its authors during the next two decades while concurrent investigations on other islands (e.g., Hearty and Kindler 1993aand 1993b, 1997Kindler and Hearty, 1995, 1997Hearty, 1998;Kindler, 1995) identified six carbonate-paleosol "couplets" (Hearty and Kaufman, 2000), spanning a time interval from the Middle Pleistocene (MIS 13) to the Holocene. More recently, geological research on Mayaguana and Crooked islands revealed the occurrence of rock units predating the Middle Pleistocene, and going as far back as the Early Miocene (Fig. 2, Table 1; Kindler et al., 2011;Godefroid, 2012;Godefroid and Kindler, 2016;Godefroid et al., 2019). ...
... EPOCHS MIS Carew and Mylroie (1985) San Salvador Hearty and Kindler, 1993a, 1993bSan Salvador Carew and Mylroie, 1995a The Bahamas Hearty and Kaufman (2000) The Bahamas Kindler et al. (2010) The Bahamas Godefroid ( Whitacre et al. (2017). More information on these diverse analytical methods and sample preparation can be found in Kaufman (2000, 2009), Hearty (2010) and Kerans et al. (2019). ...
In this paper, we formally define a series of bioclastic eolianites and protosols exposed on high-energy bank margins throughout the Bahamas archipelago as the Whale Point Formation (WPF). The position of this new lithostratigraphic unit above and seaward of deposits dated to Marine Isotope Stage (MIS) 5e and below Holocene sediments constrains its age to the latest Pleistocene, more precisely to MIS 5a (ca. 88–74 ka BP). This age is further corroborated by amino-acid racemization data calibrated with UTh ages. Based on their sedimentological characteristics, the WPF eolianites are interpreted as landward-advancing dunes decoupled from their source beaches. Relying on the faunal content, the maximum elevation of relative sea level during MIS 5a can be roughly estimated at ca. 9 ± 2 m below the present stand. The WPF includes two phases of eolian deposition separated by an interval of negative sediment budget and pedogenesis. These different facies possibly reflect millennial-scale sea-level and climate instability during MIS 5a, the latter being likely related to shifts in the mean annual position of the intertropical convergence zone and associated rainfall belt.
... The use of whole-rock (WR) AAR (Hearty and Kaufman 2000) became particularly important as the majority of outcrops consist of bioclastic and oolitic grainstones with comparatively high amino acid content (Kindler and Hearty 1996) for which the dating method is well suited. Hearty and Kaufman (2000) established that an abundance of outcrops was present, representing marine isotope stages (MIS) 1, 5a, 5e, 7/9, 11, and possibly 13/15, but there was a decreasing occurrence of older outcrops with greater age. ...
... The use of whole-rock (WR) AAR (Hearty and Kaufman 2000) became particularly important as the majority of outcrops consist of bioclastic and oolitic grainstones with comparatively high amino acid content (Kindler and Hearty 1996) for which the dating method is well suited. Hearty and Kaufman (2000) established that an abundance of outcrops was present, representing marine isotope stages (MIS) 1, 5a, 5e, 7/9, 11, and possibly 13/15, but there was a decreasing occurrence of older outcrops with greater age. To our knowledge, there are no surficial exposures older than approximately 500 ka in the Exumas, but older subaerial rocks have been described on Mayaguana Island in the southern Bahamas (Kindler et al. 2011). ...
... A recent unpublished PhD thesis by Jackson (2017; with D. McNeill as advisor) focused on the Exuma Cays and contributed a number of radiometric ages ( 14 C and U/Th), numerous additional A/I whole-rock samples, as well as other technical applications. Wholerock samples from Jackson (2017) were analyzed at the AAGL in Flagstaff, Arizona following procedures outlined Hearty and Kaufman (2000), and yielded amino stratigraphic results consistent with our previous work. Jackson (2017) also conducted drone and ground geologic mapping of several Exuma cays that were mapped earlier by Hearty. ...
The surface and subsurface geology of the Exuma Cays in the central Bahama Islands re- cords sea-level cyclicity that extends back to the Jurasssic, however the focus of this paper is the Plio-Pleis- tocene, since approximately 1–3 million years ago. During the 1990s, the rst author surveyed a large num- ber of the islands by boat, mapped the geology on 1:25,000 topographic maps with the aid of air photos, and more recently complemented these mapping studies using Google Earth Pro. In 1994, two 33 m cores were extracted from Norman’s Pond Cay and Lee Stocking Island in the southern group of the Exuma Cays. The outcropping rocks throughout the Cays are characterized by a mix of nearly pure bioclastic and oolitic sediments and limestone units. Generally, the highstand limestone deposits are capped with lowstand terra rossa paleosols, red-stained micritic limestone, calcrete, or karst surfaces. From surface and subsurface geology, a minimum of seven stratigraphic units are recorded, yet many cycles are obvi- ously missing. Three broad eustatic intervals are evident from the δ18O record. These are associated with the Pliocene-early Pleistocene (“PP” >1.2 Ma), Mid-Pleistocene Transition (“MPT” ~1.2–0.7 Ma), and the mid-late Pleistocene (“MLP” ~0.7 Ma to present). A combination of physical stratigraphy, geomorphology, paleomagnetism, and amino acid racemization (AAR) provide a general age framework for these deposits. Pliocene beds at -25 m in only one core appear to indicate slow subsidence of the Bahama Banks. An inter- val of prolonged bank marginal or lower sea stands of the MPT are indicated by a cluster of dense, clayey red paleosols. Many MLP rocks on the islands and in the cores retain sufficient amino acids to establish a relative chronology for the MLP. The geomorphic and stratigraphic succession from the Exumas shows very rapid progradation of the over-steepened bank margin toward Exuma Sound by several km since the Plio-Pleistocene. The purpose of this paper is to: 1) characterize the geology of the existing Exuma rocks and cays; 2) demonstrate the shallow-subsurface stratigraphy in two 33-m long cores; and 3) provide some examples of how the Exuma Cays and their margins have evolved over the past 1–3 million years.
... The French Bay Member is composed of a reasonably well-preserved oolite 160 exhibiting a range of environments from subtidal to intertidal to eolian (Carew and Mylroie, 1985;Caputo, 1995;Kindler and Hine, 2008). The French Bay Member has been attributed to the early part of MIS 5e based on its stratigraphic position below the radiometrically-dated Cockburn Town Member and on the basis of amino acid racemization data that suggests a MIS 5e age (Hearty and Kaufman, 2000). This lower member has been interpreted as representing a transgressive eolianite that supersedes the deposition of the subtidal Cockburn Town Member, or as possibly representing an early highstand during MIS 165 5e (Hearty and Kindler, 1993;Kindler and Hearty, 1996;Hearty and Kaufman, 2000). ...
... The French Bay Member has been attributed to the early part of MIS 5e based on its stratigraphic position below the radiometrically-dated Cockburn Town Member and on the basis of amino acid racemization data that suggests a MIS 5e age (Hearty and Kaufman, 2000). This lower member has been interpreted as representing a transgressive eolianite that supersedes the deposition of the subtidal Cockburn Town Member, or as possibly representing an early highstand during MIS 165 5e (Hearty and Kindler, 1993;Kindler and Hearty, 1996;Hearty and Kaufman, 2000). The overlying Cockburn Town Member mainly comprises coral reef boundstone or rudstone and shell-rich floatstone representing subtidal lagoonal and reef settings. ...
... The Cockburn Town member has been described as containing a prominent unconformity separating two reef units. This two-phase depositional model during MIS 5e is also supported by distinct ages 170 within the MIS 5e stratigraphy from amino acid racemization data and U-series data (Hearty and Kaufman, 2000;Skrivanek et al., 2018). At some localities, such as the type section at Grotto Beach on San Salvador Island, a shallowing upwards sequence is observed from subtidal reef and lagoonal facies to subaerial oolitic calcarenites. ...
This paper provides a summary of published sea level archives representing the past position of sea level during the Last Interglacial sea level highstand in the Bahamas, Turks and Caicos, and the eastern (Atlantic) coast of Florida, USA. These data were assembled as part of a community effort to build the World Atlas of Last Interglacial Shorelines (WALIS) database. Shallow marine deposits from this sea level highstand are widespread across the region and are dominated by carbonate sedimentary features. In addition to depositional (constructional) sedimentary indicators of past sea level position, there is also evidence of erosion, dissolution, and/or subaerial exposure in places that can place an upper limit on the position of sea level. The sea level indicators that have been observed within this region and attributed to Marine Isotope Stage (MIS) 5e include corals, oolites, and other coastal sedimentary features. Here we compile a total of 50 relative sea level indicators including 36 in the Bahamas, three in West Caicos, and a remaining 10 for the eastern seaboard of Florida. We have also compiled U-Th age data for 24 fossil corals and 56 oolite samples. While some of these archives have been dated using U-Th disequilibrium methods, amino acid racemization, or optically stimulated luminescence, other features have more uncertain ages that have been deduced in the context of regional mapping and stratigraphy. Sedimentary archives in this region that constrain the elevation of the past position of sea level are associated with uncertainties that range from a couple decimeters to several meters. Across the Bahamas and on West Caicos, one of the observations that emerges from this compilation is that estimation of sea level position in this region during Marine Isotope Stage 5e is complicated by widespread stratigraphic evidence for at least one sea level oscillation. This evidence is defined by submarine features separated by erosion and subaerial exposure, meaning that there were likely multiple distinct peaks in sea level rather than just one. To this end, the timing of these individual sea level indicators becomes important when compiling and comparing data across the region given that different archives may have formed during different sub-orbital peaks in sea level.
... Skeletal eolianites comprising Eleuthera Island are interpreted as eolian dunes and are separated from the underlying formations by paleosols (Kindler and Hearty, 1996;Hearty, 1998;Hearty and Kaufman, 2000). The authors report an inferred paleo-sea level of 0-5 m b.p.s.l. ...
... The authors report an inferred paleo-sea level of 0-5 m b.p.s.l. rather than the modern elevation of the deposit (Hearty and Kaufman, 2000;Fig. 2). ...
In this review we compile and document the elevation, indicative meaning, and chronology of marine isotope substage 5a and 5c sea level indicators for 39 sites within three geographic regions: the North American Pacific coast, the North American Atlantic coast and the Caribbean, and the remaining globe. These relative sea level indicators, comprised of geomorphic indicators such as marine and coral reef terraces, eolianites, and sedimentary marine- and terrestrial-limiting facies, facilitate future investigation into marine isotope substage 5a and 5c interstadial paleo-sea level reconstruction, glacial isostatic adjustment, and Quaternary tectonic deformation. The open-access database, presented in the format of the World Atlas of Last Interglacial Shorelines (WALIS) database, can be found at https://doi.org/10.5281/zenodo.5021306 (Thompson and Creveling, 2021).
... Skeletal eolianite comprising Eleuthera Island are interpreted as eolian dunes and are separated from the underlying formations by paleosols (Kindler and Hearty, 1996;Hearty, 1998;Hearty and Kaufman, 2000). The authors report an inferred paleo-sea level of 0 -5 m bpsl, rather the modern elevation of the deposit (Hearty and Kaufman, 2000; Figure 2). ...
... Skeletal eolianite comprising Eleuthera Island are interpreted as eolian dunes and are separated from the underlying formations by paleosols (Kindler and Hearty, 1996;Hearty, 1998;Hearty and Kaufman, 2000). The authors report an inferred paleo-sea level of 0 -5 m bpsl, rather the modern elevation of the deposit (Hearty and Kaufman, 2000; Figure 2). 370 ...
In this review we compile and detail the elevation, indicative meaning, and chronology of Marine Isotope Stage 5a and 5c sea level indicators for 39 sites within three geographic regions: the Pacific coast of North America, the Atlantic coast of North America and the Caribbean, and the remaining globe. These relative sea level indicators, comprised of geomorphic indicators such as marine and coral reef terraces, eolianites, and sedimentary marine and terrestrial limiting facies, facilitate future investigation into Marine Isotope Stage 5a and 5c interstadial paleo-sea level reconstruction, glacial isostatic adjustment, and Quaternary tectonic deformation. The open access database, presented in the format of the World Atlas of Last Interglacial Shorelines (WALIS) database, can be found at https://doi.org/10.5281/zenodo.4426206 (Thompson and Creveling, 2021).
... Only one chevron located in Miller's Settlement on Long Island has been directly dated by AAR. The authors obtained two A/I ratios averaging at 0.46 (Appendix 1), and correlated the chevron to the late Pleistocene (Aminozone E; MIS 5e II; Hearty and Kaufman, 2000). The other ridges are correlated to the latter based on their petrography, stratigraphic position and dating of associated deposits such as mega boulders or runup deposits (Hearty et al., 2002(Hearty et al., , 1998Hearty and Tormey, 2017;Kindler, 1991;Kindler and Strasser, 2000). ...
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 GBF generally overlies the Owl's Hole Formation (Carew & Mylroie, 1985;Fig. 2), which comprises both bioclastic and oolitic-peloidal calcarenites of Middle Pleistocene age (Kindler & Hearty, 1996;Hearty & Kaufman, 2000). It is capped either by bioclastic aeolianites generally correlated to MIS 5a (Almgreen Cay Formation, Hearty & Kindler, 1993;Whale Point Formation, Kindler et al., 2010) or by the Holocene Rice Bay Formation (Carew & Mylroie, 1985), which includes: (i) oolitic-peloidal aeolianites (North Point Member, Carew & Mylroie, 1985); and (ii) a shallowing-upward succession of mostly bioclastic sediments deposited in beach to dune environments (Hanna Bay Member, Carew & Mylroie, 1985). ...
... Caputo, 1995). It can be correlated with the early part of the LIG based on its position relative to the well-dated overlying unit (see below) and amino-acid racemization (AAR) data (Hearty & Kaufman, 2000). The FBM has been interpreted as transgressive-phase aeolianites of the GBF (Carew & Mylroie, 1985, 1995b, 2001, or as deposits corresponding to a distinct highstand at the beginning of MIS 5e (Hearty & Kindler, 1993;Kindler & Hearty, 1996;Hearty & Kaufman, 2000). ...
... It can be correlated with the early part of the LIG based on its position relative to the well-dated overlying unit (see below) and amino-acid racemization (AAR) data (Hearty & Kaufman, 2000). The FBM has been interpreted as transgressive-phase aeolianites of the GBF (Carew & Mylroie, 1985, 1995b, 2001, or as deposits corresponding to a distinct highstand at the beginning of MIS 5e (Hearty & Kindler, 1993;Kindler & Hearty, 1996;Hearty & Kaufman, 2000). ...
The Upper Pleistocene (Marine Isotope Stage 5e; ca 120 ka) stratigraphic record from the Bahamas comprises large, kilometre‐long parabolic ridges of oolitic composition, that point landward, and have been up to now called ‘chevrons’. A debate about their genesis has led previous researchers to consider two processes of deposition: (i) a catastrophic event involving giant storm‐generated waves produced by specific climatic conditions at the end of Marine Isotope Stage 5e; and (2) a more uniformitarian process which characterizes ‘chevrons’ as aeolian parabolic dunes because of their similar morphology. Since there are few unequivocal sedimentological criteria to discriminate aeolian from water‐deposited sediments, only a quantitative, multi‐method approach could provide enough evidence to produce a viable diagnosis on the genetic processes involved. Following this reasoning, the quantification of the morphological parameters of ‘chevrons’, a precise study of their sedimentary structures on previously and newly discovered sections, and several statistical grain‐size analyses, all advocate for an aeolian origin. Moreover, when the aforementioned characteristics of ‘chevrons’ are compared with those of storm deposits (for example, washovers) and parabolic dunes occurring elsewhere on Earth, the dissimilarity with the former and the resemblance with the latter is evident. Amino‐acid racemization dating, together with stratigraphic and petrographic investigations, constrain the age of the ‘chevrons’ to the late part of Marine Isotope Stage 5e. Their occurrence during this specific time interval can be explained by both strengthened easterly winds and drier climatic conditions associated with changing vegetation cover. Fixation of the arms by sparse vegetation, coupled with the loose ‘chevron’ nose sediment migrating farther inland, form the peculiar U‐shaped morphology of these ridges.
