Sedimentology of lower Cretaceous sediments from the east Antarctic margin

Site 693 sediments have organic contents lower than those at Site 692. Glauconite is common, and three thin limestone beds are present in the upper part of the unit. Well-preserved diatoms, radiolarians, and diatomite layers suggest that the sediments were deposited under conditions of high productivity.

Ashclay layers with well-preserved glass shards indicate volcanic activity at the time of deposition. The sediments at both sites were deposited in an upper bathyal (500-1000 mbsl) marine environment under primarily dysaerobic conditions. At Site 692 the sediment may have experienced periods of anoxia.

The sediments at Site 693 record the beginning of oxygenation along the Antarctic margin during the Albian at about the same time as on the Falkland Plateau.