Cenozoic structural and stratigraphic history of McMurdo Sound, Antarctica

Abstract

During the austral summer of 2004 the RVIB Nathanial B Palmer (NBP0401) collected 2000 km of multi-channel and 500 km of single-channel seismic data over the Terror Rift and western Victoria Land Basin (VLB), McMurdo, Antarctica. Data were collected to expand marine and ice-shelf seismic coverage of McMurdo Sound to enable the recognition of basin-wide climatic and tectonic events through analysis of sub-surface horizons. Collected data were integrated with existing reflection data from McMurdo Sound and with age data from Cape Roberts (CRP) and CIROS holes. The stratigraphic framework developed is based on distinct, regionally traceable horizons that correspond to significant and recognizable changes in glacio-marine sequence geometry and can be interpreted as recording basin-wide climatic and tectonic events for the period 0-17 Ma. Older sequences cored at CRP and CIROS could not be mapped since they are below the seafloor multiple. The lowermost stratigraphic unconformity event interpreted (H10, 17 Ma from CRP) can be traced for many kilometres in both coast-parallel and coast-normal directions. Above this boundary the seismic data reveal a sedimentary succession in the Erebus Moat that reaches up to at least 3 km in thickness. Seismic horizons and units were correlated with tectonic rifting and loading episodes of the VLB, Terror Rift and Ross Island, as well as the Antarctic's fluctuating glacial history to resolve a depositional history over time. Formation ages were estimated for six horizons based on correlation with tectonic and climatic events. Deposition geometries and seismic facies observed reveal; (1) changing influences on accommodation space production, including extension of the VLB and Terror Rift, and loading of Ross Island, (2) a progressively cooling glacial/interglacial depositional environment since 17 Ma, and (3) changing glacial erosion patterns possibly due to the influence of Ross Island. Inferred sedimentation rates and facies patterns in McMurdo Sound support the existence of a stable East Antarctic ice-sheet since the Mid-Miocene.