Seismic Reflectivity Analysis of Regional Unconformities on Ross Sea Continental Shelf: A Geophysical Fingerprint for Antarctic Ice Sheet Grounding Surfaces

Adeniyi Saanumi, Louisiana State University, Baton Rouge, Department of Geology & Geophysics, Baton Rouge, Louisiana USA. [email protected]

Past seismic stratigraphic studies along the continental shelf of Antarctic passive margins interpreted regional glacial unconformities as Cenozoic ice-sheet grounding surfaces. These unconformities are manifested on seismic profiles as reflectors exhibiting regional extent and cross-cutting relationships between underlying and overlying units. In the Ross Sea, Antarctica, we model the offset-dependent seismic reflectivity patterns of these unconformities as an alternative to using stratal patterns . Six multichannel seismic lines were run in the North-Basin sector of Ross Sea outer continental shelf in 2003.  In an attempt to characterize interpreted glacial unconformities using offset-dependent reflectivity, moveout-corrected common midpoint data are stacked to highlight differences in the reflector continuity and amplitudes between various offset-dependent attribute sections.  Amplitude variation with offset analysis indicates a contrast in rock properties between proglacial deposits and glacio-marine deposits.  Regional unconformities were found to partly coincide with reflectors exhibiting high gradient and intercept on attribute stack. Quality and resolution of seismic data may have limited the understanding and description of regional unconformities. Non-uniqueness of offset dependent anomalies is also a concern.