Sequence Stratigraphic Framework of Carbonate Diagenesis within Neogene Glaciomarine Sandstones of the Victoria Land Basin, Antarctica: Insights into Reservoir Quality in Polar Settings

The controls on reservoir quality of most clastic sedimentary deposits are well-documented and understood. However, comparatively little is known about the reservoir potential of glaciogenic and glaciomarine deposits. This study investigates the Neogene strata of the AND-2A core recovered by the ANDRILL-Southern McMurdo Sound Project in the Victoria Land Basin, Antarctica, as an analog for assessing controls on reservoir quality in glaciomarine deposits. A petrographic analysis was conducted on 60 sandstone samples from various depths throughout the core, and carbonate diagenetic phases and morphologies were documented. Four sequences were examined in detail. Point counting on all samples was done to determine percentages of cement, porosity, detrital mud, and framework grains. Results show that reservoir quality in glaciomarine sandstone is dramatically affected by the presence of diagenetic carbonate and strong correlations exist between carbonate cement abundance, paleoclimate, and sequence stratigraphic systems tract. Sandstones that formed during the coldest (polar and subpolar) climate regimes have relatively low porosities ( Decreased input of fine-grained sediments during colder climate regimes resulted in higher permeability deposits that were prone to infiltration by brine upon burial. By contrast, many texturally mature sandstones deposited in highstand deltaic settings during more temperate climate regimes preserve higher porosities (25 – 45%) and lack significant cementation. Sequence stratigraphic relationships indicate that these porous sandstones are best developed in highstand delta systems that formed during ice minima, when substantial volumes of meltwater were released from glacier termini. Individual sandstone bodies, which likely extend laterally over several kms, tend to be enclosed by muddy lithologies. Porosity in these sandstones was retained due to discharge of dilute meltwater during deposition and subsequent isolation of sands between impermeable barriers. Patterns identified in this study may prove useful in predicting and locating target reservoirs in other glaciogenic and glaciomarine settings worldwide. Advisors: Tracy D. Frank and Christopher R. Fieldin