Tectonic-sedimentary architecture of surficial deposits along the continental slope offshore Romania (North of the Viteaz Canyon, Western Black Sea): Impact on sediment instabilities

Abstract

The upper continental slope offshore Romania is a complex area hosting turbidite deposits, multiple types and ages of deep-seated faults, gas hydrates, gas-escape features, and numerous Mass Transport Deposits (MTDs). Multi-scale seismic data sets (2D-high-resolution and near-bottom very high-resolution) were used to study the interaction between such disparate geological features and determine their impact on slope stability. At least five main paleo-valleys have been identified in the north of the Viteaz (Danube) canyon/valley. The most recent channelized systems linked to these valleys formed over a basal layer of MTDs. These MTDs are associated with an unconformity corresponding to the Base Neoeuxinian Sequence Boundary formed during the last major sea-level fall. This erosional surface shows scarp alignments that coincide with underlying faults. We argue that gravity-driven fault reactivation, with possible upward gas/fluid migration along these faults, is a determinant factor controlling sedimentary instabilities. Numerous MTDs are also observed during channel-levees building and reveal local sediment instabilities related to localized erosional process in the canyon. Finally, MTDs recorded within the upper draping unit, suggest that sediment instability also occurred during recent sea level highstand. Sediment pulse, seismicity, and gas hydrates dynamics can also play a determinant role in sediment instability throughout the sediment record.