Site 647 ( ODP).

Rotary and APC cores provide a nearly complete sequence over the last 2.5 m.y. of deposition (late Pliocene-Pleistocene). Recognizable alternations of relatively nannofossil-rich silty clay and more gravel-rich, silty intervals appear to represent depositional cycles related to glacial-interglacial climatic changes. Sedimentation rates average about 46 m/m.y. (4.6 cm/k.y.) . Sediment deposited over the last 1.2 m.y. contains more silt, sand, and detrital carbonate than the older part of Lithologic Unit I. A suite of ice-rafted pebbles could have been derived from a broad region, including carbonate terrains in the northern Baffin Bay area. As at Site 646, the onset of glacial ice rafting occurred at about 2.5 Ma.-from Authors