Antarctique

Antarctic Offshore

Weddel Sea

This Canvas autotrace of a seismic profile of the Weddel Sea crossing the outermost continental shelf, shelf edge and slope of the Crary Trough Mount Fan illustrates several truncations (termination of strata or seismic reflections interpreted as such, along the upper unconformity of a stratigraphic cycle, which is created by erosion, which was, generally, tectonically enhanced (angular unconformity) and toplaps (geometric relationship determined by the termination of strata or seismic reflectors, against an overlying surface, which can be created by erosion or absence of deposition), which allow to highlight , at least, five sequence-cycles individualized by unconformities, i.e, by erosional surfaces induced by a relative sea level falls, which may produce an absence of parallelism of the strata to the limits of the stratigraphic cycles. In spite of the fact that the internal configuration of the reflectors is progradational, in some case the progradations are oblique (outbuilding without upbuilding) and others are sigmoid (outbuilding with upbuilding).

This tentative interpretation illustrates the trigger of turbidite currents in association with the movement of syn-sedimentary normal faults, which seem to be the responsible for the submarine slope fans (colored in yellow), independently of sea level changes. In fact, at such a water depth, there is accommodation enough, i.e., there is space available for deposition, if the turbidite currents were triggered. Note on the sea floor the presence of active channels, controlled by local extensional tectonic regimes, along which the contour currents seem to flow.