Sedimentology and stratigraphy of McMurdo Sound and the Ross Sea, Antarctica: Implications for glacial history and analysis of high-latitude marginal basins
Bartek, Louis Robert, III
Anderson, John B.
Doctor of Philosophy
Piston core, drill core, and high resolution seismic data from McMurdo Sound were analyzed and tied to litho- and seismic stratigraphic events in the Ross Sea. The data show that the first extensive ice sheet grounding event occurred in the Ross Sea as early as late Oligocene time. Development of the East Antarctic ice sheet, and Oligocene ice sheet grounding may have been triggered by the opening of a seaway between Antarctica and Australia during late Cretaceous/early Paleogene time. As the seaway formed, moist air was advected over the cold Antarctic continental landmass. This led to increased precipitation on Antarctica and to the development of an Antarctic ice sheet by at least late Eocene time. Marine-based ice sheets appear to have waxed and waned on the Ross sea continental shelf since the Oligocene grounding event. These waxing and waning events are thought to be responsible for the development of a global Neogene stratigraphic signature. Stratigraphic analysis of seismic and drill core data from the Ross Sea suggests that the stratal geometry and thickness of glacial marine deposits is strongly controlled by the rate of glacial waxing and waning and the availability of accommodation space which in this instance is largely controlled by basin subsidence. Thick offlapping sequences form when the accommodation is high and glacial fluctuation rates are low, and thin flat-lying sequences are deposited when accommodation is low and glacial fluctuation rates are high. A new statistical technique was devised in order to analyze the complex facies relationships that are found in the stratigraphy of McMurdo Sound. Generally, these analyses show that infilling of the basin has been asymmetric. Volcaniclastic debris dominates the eastern portion of the Sound, while deposition of biogenic, ice-rafted and eolian transported debris, and basal till (during glacial maxima) infills the western Sound and central basin. During temperate interglacial events, meltwater transported debris may play an important role in infilling the Sound. Sedimentation on the volcaniclastic apron of the eastern slope of McMurdo Sound is dissimilar to most submarine fans. It is characterized by a reversal in the distribution of proximal and distal facies.