Canyon morphology on a modern carbonate slope of the Bahamas: Evidence of regional tectonic tilting

Abstract

International audienceNew 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-fl ow 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 fi lled with recent sediment. Canyons have amphitheater-shaped heads resulting from coalescing slump scars, and are fl oored 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 fi ne particles and fl ow 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

Seismic-sequence stratigraphy and geologic structure of the Floridan aquifer system near "Boulder Zone" deep wells in Miami-Dade County, Florida

“…others (1999, 2002). To the east of the Florida Platform, Mulder and others (2013) reported observations that are consistent with late Cenozoic westward tectonic tilting on the Little Bahama Bank, which is temporally compatible with the uplift and reverse faulting shown in figure 13. The timing of the uplift and movement along these reverse faults is also consistent with the occurrence of a widespread compressional event in the late Miocene and early Pliocene that Missimer and Maliva (2004) proposed as the source of folding in southern Florida.…”

Margin collapse and slope failure along southwestern Great Bahama Bank

“…This observation is corroborated by multibeam bathymetry data (Mulder et al, 2012b). During the Pliocene however, numerous small-scale downslope movements and slump masses occurred on a detachment surface (Harwood and Towers, 1988).…”

“…It is commonly thought that failure is more pervasive on the uncemented lower slope than the steep cemented margin. Seismic data from northern Little Bahama Bank reveal numerous slump scars on the lower slope at water depth N550 m (Mullins et al, 1984;Mulder et al, 2012b). There the slope failure occurrence is related to the less cemented lower slope.…”

“…The steep cemented slope only shows small, localized slope failures with 10-100's of meters width (Grammer et al, 1993). Catastrophic large-scale slope failures, however, have been documented in the un-cemented slope (Harwood and Towers, 1988;Mulder et al, 2012aMulder et al, ,2012b.…”

Tectonics of the Dalrymple Trough and uplift of the Murray Ridge (NW Indian Ocean)

“…Second, the uplift of the northern Murray Ridge since~1.9 ± 0.9 Ma might account for the Pleistocene southwestward migration of the Indus canyon on the Indian Margin (Kolla and Coumes, 1987). A precise dating of the episodes of migration of the canyon, together with reconstructions of the evolution of the topography fossilized by channel-levee systems, would highlight the complex interaction between tectonic and sedimentary processes (see similar examples in Mulder et al, 2012).…”