Alfred Wegener Institute for Polar and Marine Research, Federal Republic of Germany

In this study, we investigate the stratigraphy of a trough-mouth fan in the Weddell Sea to determine possible relationships between basin-floor stratigraphy and glaciation on Antarctica. Seismic data from the basin floor show a deep, broad, and elongate erosional channel filled by thick chaotic-facies deposits, basin-floor fans, and channel-levee deposits. From seismic-stratigraphy analysis of basin-floor stratigraphy, we infer that this channel formed by large-volume mass wasting sourced from poorly sorted glacial sediments from Crary Trough-Mouth Fan and Dronning Maud Land slopes. Correlation to ODP Leg 113 Site 693 suggests that the mass wasting of the slopes occurred in the early Pliocene. We surmise that collapse occurred during an early Pliocene interglacial and was related to major drawdown of the antarctic ice volume. Collapse was probably triggered by rebound and relative sea-level fall, a mathematically predicted geoidal effect related to antarctic ice-volume reduction. The record of this major ice-volume reduction is not manifest in the trough-mouth fan but rather is manifest in the basin-floor stratigraphy as a major backfilled erosional channel, which extends far beyond the trough-mouth fan.