Extent of the grounded Antarctic ice sheet in space and time

Limited exposure is a major drawback when using drillcores for
reconstructing past glacial environments: direct observations of
sediments are restricted to the width of the cores and only provide a
scattered view of former 'depositional situations'. Still, in
offshore settings like the Antarctic continental shelf, drillcores are
often the most valuable sources of information available. It is
therefore not surprising that in the studies of Marguerite Bay,
Antarctic Peninsula, Pine Island Bay, West Antarctica and the Ross Sea
conventional sedimentological techniques proved to be inconclusive
concerning some aspects in the unravelling of the glacigenic
record. The difference between basal tills and proximal glacimarine
sediments, for example, was often far from clear. To force a
breakthrough in this impasse, micromorphological data can be used to
distinguish the two, and may subsequently be used to pinpoint the
former positions of the Antarctic grounding line.