Stratigraphic Architecture of “Greenhouse” and “Ice House” Sequences on a Glaciated Continental Margin: An Example from the Ross Sea, Antarctica

Howard Preston Viator and Louis R. Bartek
University of North Carolina, Chapel Hill, Chapel Hill, NC

Nearly 715 km of high-resolution and multi-channel seismic reflection data were acquired from an updip locale on the Ross Sea continental margin (Antarctica) in an investigation of the evolution of the Antarctic cryosphere. These data were collected within a grid (≈ 3 km X 3 km) that is orientated parallel and perpendicular to the strike of the modern shelf edge. Correlation of these data to published profiles and to DSDP drill sites in the Ross Sea facilitates examination of the regional extent of the stratigraphy and provides age contraints and the lithofacies associated with the units. Earliest, Early Miocene strata from this locale comprise parallel, laterally-continuous, moderate frequency and moderate to low amplitude reflections of relatively uniform thickness that are associated with diatomaceous, pebbly mudstones. The pebbly mudstones are interpreted as a glacial marine facies associated with limited ice extent in the Ross Sea (a Cenozoic “Greenhouse” interval). Latest Early Miocene strata consist of relatively reflection-free seismic facies of variable thickness, containing scattered low to moderate, low frequency trough-shaped reflections. This facies is similar to Pleistocene strata that are associated with extensive ice sheet grounding on the continental margin during “Ice House” intervals. These “Ice House” and “Green House” architectures correlate to eustatic lowstands and highstands and to heavy and light oxygen isotope events, respectively. “Ice House” stratigraphy is present within the Middle and Late Miocene and Late Pliocene through Pleistocene successions of the Ross Sea while “Greenhouse” Stratigraphy is associated with Early Miocene and Early Pliocene successions of the Ross Sea.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005