Abstract

The Gebra–Magia Complex is an important example of a submarine mass-movement composite located on the lower continental slope of the Antarctic Peninsula (Central Bransfield Basin). Continuous instability dynamics over time is inferred to have affected the palaeo-trough-mouth fans present in the study area.

The depositional architecture and the outstanding relief of the Gebra Valley, which is the most striking morphological feature in the area, determine the asymmetrical morphology of the complex. This complex is characterized, from east to west, by an open-slope margin flanking the sidewall of the Gebra Valley, the Gebra Valley itself and a SW margin that is connected to the Magia area by a large scar approximately 7.8 km to the SW.

The Gebra Valley is a Quaternary debris valley resulting from repeated large-scale mass-transport and cut-and-fill processes. In contrast, the Magia area is dominated by unchannelized sedimentary instability processes, resulting in a different sedimentary architecture and morphology. The near-surface sediments in the Gebra–Magia Complex document the continuous occurrence of recent mass movements, as also evidenced by flows transported downslope as unchannelized or channelized flows.

Climate and tectonic activity are considered the primary factors controlling the development of the complex.