Clast Shape as an Indicator of Transport and Depositional Mechanisms in Glacial Marine Sediments: George V Continental Shelf, Antarctica

Floating ice deposits (paratills) and grounded ice deposits (orthotills) have been identified on the continental shelf bordering the George V. Coast, East Antarctica. They are recognized on the bases of texture, pebble fabric, presence or absence of fauna, and stratification. The shapes of over 200 clasts taken from these glacial-marine tills indicate transport in basal debris zones. Clast shapes imply passive deposition of paratills from floating ice as supported by other lines of evidence. Deposition of orthotills by melt-out processes is also suggested by clast shape analysis. Melt-out till deposition is untenable on theoretical grounds, however, and a passive form of lodgment till deposition is proposed for orthotills in this area.