Lateral migration of large sedimentary bodies in a deep-marine system offshore of Argentina

Contourite features are increasingly identified in seismic data, but the mechanisms controlling their evolution remain poorly understood. Using 2D multichannel reflection seismic and well data, this study describes large Oligocene- to middle Miocene-aged sedimentary bodies that show prominent lateral migration along the base of the Argentine slope. These form part of a contourite depositional system with four morphological elements: a plastered drift, a contourite channel, an asymmetric mounded drift, and an erosive surface. The features appear within four seismic units (SU1-SU4) bounded by discontinuities. Their sedimentary stacking patterns indicate three evolutionary stages: an onset stage (I) (similar to 34-25 Ma), a growth stage (II) (similar to 25-14 Ma), and (III) a burial stage (< 14 Ma). The system reveals that lateral migration of large sedimentary bodies is not only confined to shallow or littoral marine environments and demonstrates how bottom currents and secondary oceanographic processes influence contourite morphologies. Two cores of a single water mass, in this case, the Antarctic Bottom Water and its upper interface, may drive upslope migration of asymmetric mounded drifts. Seismic images also show evidence of recirculating bottom currents which have modulated the system's evolution. Elucidation of these novel processes will enhance basin analysis and palaeoceanographic reconstructions.

Automated summary

Contourite features are observed along the base of the Argentine slope, showing lateral migration of large sedimentary bodies and four main morphological elements. The sedimentary stacking patterns suggest three evolutionary stages, indicating that lateral migration is not limited to shallow marine environments. The study highlights the influence of bottom currents and secondary oceanographic processes on contourite morphologies and provides insights into basin analysis and paleoceanographic reconstructions.