However, the unusually cold Antarctic ice sheet in the Pleistocene, which experienced a large externally imposed sea-level signal from Northern Hemisphere glaciation, may not be an entirely appropriate model for earlier glaciations. A forum on polar seismic stratigraphy centered on the extent to which glacially derived sediments could be unambiguously identified on seismic profiles to guide future seismic data acquisition and assess priorities for direct sampling. Discussion revolved fundamentally around scale. Detailed mapping of some Northern Hemisphere shelves was used to argue that some very small-scale features are unambiguously glacial. Recognizing these small features within seismic sequences required high-frequency survey with small line spacing, which is not effective at great depth and not always feasible in the Antarctic.
Glacial environments have highly varied sedimentary expression.
The record of polar glaciers, with negligible basal melt-water and sediment outwash, is dominated by massive subglacial facies. Besides depositing sediment at their termini, such ice streams may widely erode the continental shelf with greatest erosion on the inner shelf. Participants discussed acoustic features of glaciated shelves. Regionally flat erosional unconformities on the shelf far below wave base suggest erosion by extensive grounded ice sheets during times when the shelf was overdeepened. Not all of these glacial features would be present in a particular area, and some might be difficult to identify at depth.