Carbonate Mass-Transport Deposits (MTDs): Comparing Carbonate Slopes of the Great Bahama Bank and Apulian Carbonate Platform

Large carbonate platforms shed huge volumes of sediment onto their adjacent slopes. Resulting carbonate successions are comprised of gravity-flow beds (turbidites, debrites), which are occasionally reworked into mass-transport deposits (MTDs) by the failure of differentially lithified portions of slope strata. Despite their significance in the depositional record, the internal architecture of MTDs along sediment-producing carbonate platforms is poorly understood. This study compares carbonate-slope-derived MTDs imaged in seismic reflection data from Miocene–Recent deposits in the Bahamas, with those observed in outcrops of the Cretaceous Apulian carbonate margin in the Ionian Basin in Albania. Understanding the large-scale (kilometers to tens of kilometers) internal architecture of MTDs in seismic is crucial for identification of these structures in outcrop. In turn, only outcrop studies allow the detailed analysis of the reworking style within these massive sediment bodies at a smaller scale (meters to kilometers). The internal architecture of the studied carbonate MTDs testifies to the existence of an along-slope continuum of deformation structures, characterized by vertical partitioning into distinct mass flows during single mass-transport events. Mass-wasting processes are inferred from strain-partitioning structures, recording along-slope and slope-parallel architectural heterogeneities. Three deformation domains are recognized: extensional headwall domain, translational body domain, and contractional toe domain. The development of shear surfaces, rather than ductile shear zones, in the body and toe domains presents predictive (in modern environments) and diagnostic criteria (in fossil examples) of mass-wasting events along carbonate slopes.