Colorado College, United States

Marine geophysics was used to investigate the structural framework and tectonic history of the eastern border of the Ross Sea Rift and to integrate this with what is known of Marie Byrd Land. The region is characterized by a passive margin with a flat shelf cut by the Miocene Colbeck Trough. Seismic sequences and unconformities of the Ross Sea areas were correlated with the Colbeck region. Late Oligocene and younger sections unconformably overlay Early to Late Cretaceous and early Tertiary sequences. This unconformity is underlain by two units interpreted as syn-rift units. The onshore and offshore region was widely faulted in Early and Late Cretaceous time and subsided during Late Cretaceous and Cenozoic time. Detachment-style extension is indicated for the late Early Cretaceous. Tilting of the shelf occurred in late Cenozoic due to continued subsidence of the shelf and uplift in western Marie Byrd Land. Further study of the dating of the units sampled in this study will provide additional correlation. (Mod. auth. abstr.)