Soft-sediment deformation and kinematics of vigorous basal interaction within a submarine mass-transport deposit; a case study from Cerro Bola, Argentina

Mass Transport Deposits (MTDs) are considered to be one of the major process responsible for the redistribution of sediments from the shelf break into deep water and are also responsible for modifying their surroundings The... [ view full abstract ]

Mass Transport Deposits (MTDs) are considered to be one of the major process responsible for the redistribution of sediments from the shelf break into deep water and are also responsible for modifying their surroundings
The Late Paleozoic Paganzo Formation preserved at Cerro Bola provides exceptional 3-D exposure through the Paganzo Basin of northwestern Argentina, and exposes an 8-kilometre strike section through a mid to late Carboniferous succession, comprising fluvio-deltaic sediments, turbidites and MTDs. We here present field evidence of a vigorous interaction between a MTD and the underlying fluvio-deltaic substrate. The resulting deformation is described using aerial photo interpretation and field observations, including flow kinematic estimation from fold orientation data, in order to better understand the interaction between the MTD and the substrate. The succession exposes a seismic scale MTD up to 180 metres thick, one of whose main characteristics is the preservation of large, relatively undeformed allochthonous sandstone blocks, which are preserved throughout the whole MTD. The sandstone blocks are typically larger and more abundant towards the MTD base where they comprise up to ~30% of the MTD volume. These blocks were derived from the underlying substrate, from which they were eroded and incorporated into the MTD during transport; such process resulted in local scours, gouges and grooves along the basal contact of the MTD. The incorporation of substrate blocks requires a certain degree of shear stress penetration into the substrate in order to initiate failure planes. Evidence for such shearing is provided within the uppermost few tens of metres of the fluvio deltaic sediments, where large-scale fragmentation, proto-block formation, boudinage, pinch-and-swell structures, and abundant recumbent folds are observed. Measurements of fold hinges and axial planes provide good kinematic indicators that accord with the main transport direction of the MTD towards the NW