The cores of sediments in the northeast Pacific Ocean, collected by the University of Washington, contain several sand-silt layers. Most of the layers and cores occur at locations 500-700 miles from the shores and at

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depths exceeding 2,000 fathoms. All sand-silt layers have sharp contacts, with no visible gradation between layers.

The texture and composition of these layers is fairly uniform. The sediments are well sorted. Quartz is the predominant light fraction; feldspar the next in abundance. The heavy-mineral content of these layers ranges approximately from 5 to 15 per cent. Hornblende is predominant and hypersthene is abundant in the northern part of the region, whereas biotite and muscovite are abundant in the southern part of the region. Chemical decay has had little or no effect on the minerals during and after deposition.

The source of these sand-silt layers is considered to be continental, judged from their texture and composition. Each layer appears to have a similar transportation and depositional history, and each is probably a turbidity-current deposit. Differences in heavy-mineral composition occur because of differences in provenance.

Carbon-14 dating of sediment cores collected near these layers and the stratigraphic position of these layers show them to have been deposited during part of Wisconsin time.

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