Interpretation of multi-channel seismic data from the Ross Sea, Antarctica

Abstract

Analysis of multi-channel seismic data from the Ross Sea, Antarctica, reveals five Cenozoic subbasins (Eastern, Northern, Central, and Central High basins and Central Trough), separated by structural highs and faulted blocks (Central and Coulman highs and Hallett Ridge). The subbasins show a typical rift-basin development: faulted basement and synrift and postrift sedimentation separated by an unconformity. The maximum depths of the Eastern, Central, and Northern basins, Central Trough, and Central High Basin are about 10,000 m, 7,000 m, 5,000 m, 4,000 m, and 3,000 m, respectively. Restoration of a depth-converted seismic profile crossing the Central High, Central High Basin, Central Trough and part of the southernmost Coulman High suggests that the postrift subsidence was interrupted by local uplift in the late Early Miocene. Seismic profiles from the Eastern Basin were interpreted further to investigate the evolution of sedimentary sequences along the western and southwestern margins of the basin. Postrift sedimentation evolved from a ramp phase to a regressive shelf-slope phase in the middle Early Miocene. The shelf margin appears to have prograded northeastward in the late Early Miocene and Late Miocene-Early Pliocene. The shelf-margin progradation in the late Early Miocene is characterized by sigmoidal clinoform and accompanied by a distinct prograding package in the upper shelf, formed probably beneath the grounded ice. The self margin progradation in the Late Miocene-Early Pliocene is characterized by steep foreset and eroded topset beds, typical of till deltas formed in front of advancing ice. The shelf-margin progradation may be related to the growth of the West Antarctic Ice Sheet. Each phase of progradation was followed by aggradation.