Sedimentary dynamics and high-frequency sequence stratigraphy of the southwestern slope of Great Bahama Bank

Abstract

New geophysical data from the leeward slope of Great Bahama Bank show how contour currents shape the slope and induce re-sedimentation processes. Along slope segments with high current control, drift migration and current winnowing at the toe of slope form a deep moat. Here, the slope progradation is inhibited by large channel incisions and the accumulation of large mass transport complexes, triggered by current winnowing. In areas where the slope is bathed by weaker currents, the accumulation of mass transport complexes and channel incision is rather controlled by the position of the sea level. Large slope failures were triggered during the Mid-Pleistocene transition and Mid-Brunhes event, both periods characterized by changes in the cyclicity or the amplitude of sea-level fluctuations. Within the seismic stratigraphic framework of third order sequences, four sequences of higher order were identified in the succession of the upper Pleistocene. These higher order sequences also show clear differences in function of the slope exposure to contour currents. Two stochastic models emphasize the role of the contour currents and slope morphology in the facies distribution in the upper Pleistocene sequences. In areas of high current influence the interplay of erosional and depositional processes form a complex facies pattern with downslope and along strike facies alterations. In zones with lower current influence, major facies alternations occur predominately in downslope direction, and a layer-cake pattern characterizes the along strike direction. Therefore, this study highlights that contour currents are an underestimated driver for the sediment distribution and architecture of carbonate slopes.

Neogene palaeoceanographic changes recorded in a carbonate contourite drift (Santaren Channel, Bahamas)

“…This additional volume of periplatform deposits built a sediment wedge and pushed the moat westward (Fig. E and F) in addition to redeposited material by slope failures which filled the former moats (Wunsch et al ., ). Winnowing has prevented further westward migration of the slope since the middle Pleistocene (Wunsch et al ., ) probably by the extension of the volume through flow.…”

“…In the Bahamas archipelago contourite drifts are abundant in the seaways and consist mostly of periplatform ooze, that is, a mixture of particles derived from the shallow‐water platform interior and pelagic organisms (Betzler et al ., , ,b, ; Lüdmann et al ., , ; Tournadour et al ., ; Chabaud et al ., ). The contourite drifts around the Bahamian Archipelago and their interaction with sedimentation processes have been the subjects of research over the last decades (Neumann & Ball, ; Mullins et al ., ; Betzler et al ., , ; Anselmetti et al ., ; Tournadour et al ., ; Chabaud et al ., ; Wunsch et al ., , ). The Santaren Channel (SC), a 50 to 65 km wide seaway, separates two carbonate banks of the Bahamian archipelago (Fig.…”

Contour current imprints and contourite drifts in the Bahamian archipelago

“…Most of the aforementioned references deal with siliciclastic systems and literature about carbonate contour current‐related systems is rare (Bein & Weiler, ; Cook & Mullins, ), with the few examples known consisting of periplatform ooze with minor clayey intervals. Most studies deal with Bahamian slopes in particular; including, the Little Bahama Bank (Mullins & Neumann, ; Mullins et al ., , ; Austin et al ., ; Harwood & Towers, 1988; Rendle et al ., ; Rendle‐Bühring & Reijmer, ; Lantzsch et al ., ; Mulder et al ., ; Rankey & Doolittle, 2012; Tournadour et al ., ; Chabaud, ; Chabaud et al ., ), the Great Bahama Bank (Brunner, ; Eberli et al ., ; Bergman, ; Mulder et al ., ), the Santaren Channel (Anselmetti et al ., ; Lüdmann et al ., ; Wunsch et al ., ), the Tongue of the Ocean (Schlager & Chermak, ; Grammer & Ginsburg, ; Grammer et al ., ) and Exuma Sound (Crevello & Schlager, ; Austin et al ., ; Grammer et al ., ). Other examples are reported from the Maldives (Lüdmann et al ., , ) and in ancient environments (Hüneke & Stow, ).…”

Carbonate drifts as marine archives of aeolian dust (Santaren Channel, Bahamas)

“…for location) reveal a sedimentary succession composed of nannofossil ooze with planktonic foraminifera, echinoderm spines, pteropods and peloids, and intercalated hardgrounds, as well as up to 20 cm thick beds enriched in clay and silt (Eberli et al ., ). The comparison of core 166‐1006B with Parasound line PS‐006 shows a close correlation between the latter and acoustic high‐amplitude horizons (Wunsch et al ., ). Similar observations were made on core GeoHH‐M95‐524 where a pronounced high‐amplitude reflection correlates with a 7 cm thick partly lithified packstone interval at 3·77 m bsf (Figs and ).…”

“…). The drift body is lined by current moats towards the slopes of GBB and CSB (Anselmetti et al ., ; Lüdmann et al ., ; Wunsch et al ., ; Paulat et al ., ). These moats form shallow sea floor depressions (up to 22 m deep) of varying width.…”