Large sub-tropical carbonate platforms export vast quantities of sediment onto their adjacent slopes. Mass Transport Deposits (MTDs: including slides, slumps and debrites) and calciturbidites occur within carbonate slope deposits. In this study, MTDs of The Bahamas are compared with those of the Cretaceous Apulian carbonate margin in Albania. The characterization of the internal architecture of MTDs in seismic is crucial toward accurate paleoslope reconstructions in outcrop. Vice versa, outcrop studies provide the details of strata reworking within these massive sediment bodies at metre to kilometre-scale. In addition to a longitudinal continuum of deformation, MTDs show evidence of vertical partitioning of the mass flows. Mass-wasting processes can be assessed from strain partitioning structures in MTDs, recording longitudinal (along-slope) and lateral (slope-parallel) heterogeneities. Three deformational domains are defined based on the dip-oriented continuum of structures: extensional (headwall domain), translational (body domain) and contractional (toe domain). Confined MTDs are limited by steep and deep lateral margins that mark the boundaries between failed deposits and undisturbed strata. In unconfined MTDs, resedimented material can overstep the frontal ramp and lateral margins, forming prominent fold structures in response to layer-normal and layer-parallel shearing. The internal architecture of the toe domain reveals vertical strain-partitioning expressed in seismic as the stacking of high-amplitude continuous and discontinuous, and chaotic low-amplitude reflectors revealing an increasingly reworked pattern upwards. Such vertical segregation is also observed in outcrop, with partitioning occurring along diffuse or sharp sub-horizontal internal shear surfaces. As strata reworking increases with transport distance, top-down reorganization of failed strata occurred during failure. The uppermost plastic, more mobile part of sediment mass deformed the underlying, poorly lithified strata. Intense folding here is testified by recumbent folds and interfold limb break-off. The lower part of MTDs exposes non-coaxial folds indicative of movement direction. The basal shear surface is characterized by fault-propagation folds and incipient folding. In this study large-scale MTD structures displayed in seismic profiles from the Bahamas could be linked to detailed features observed in seismic-scale MTD outcrops in Albania.
Monday October 5, 2020, starting at 5:00 PM +04
Johan Le Goff
Post-Doctoral Researcher, Geosciences Department, KFUPM
Johan Le Goff has an interest for marine sedimentology with a focus on processes governing the architecture of carbonate slopes. He holds a B.Sc. & a M.Sc. degree (2010) in geology from ENSEGID-Bordeaux, and a Ph.D. (2015) from ENSEGID-Bordeaux (France) and the KU Leuven (Belgium). In 2016, he integrated the working group on modern carbonate slopes (Bahamas project) at the University of Bordeaux. Since 2017, he works as a post-doctoral researcher at KFUPM-CPG (Saudi Arabia).

Currently, Johan Le Goff focusses on density-flows and their preservation in the sedimentological record. He initially used field mapping, drone survey and sediment description at the outcrop to provide insights into the stratigraphic architecture, depositional processes, and reservoir characteristics of ancient carbonate slopes (e.g. Albania, Italy). His research then evolved toward the integration of ancient datasets with measurements from modern systems (e.g. bathymetry, seismics, sediment coring). This comparative sedimentology approach enables processes and product to be better constrained both in the ancient and modern carbonate slopes record.
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