Much of the inner shelf off Washington is filled with well-sorted, positively to extremely positively skewed, and leptokurtic to extremely leptokurtic sediments having mean sizes between 2-3^phgr and 3-4^phgr. Gravel-rich sediments are common opposite and north of Cape Flattery, and at about depths 14-18 fm and 28 fm opposite Grays Harbor and at 14-28 fm opposite Quinault River. Only rarely are the sediments finer than sand size. These gravel and fine sediments are relatively poorly sorted compared with the other sediments.

The pebbles constituting the gravel-rich sediments are smooth and rounded. Thin-section study of the pebbles from opposite Grays Harbor reveals the following rock types: (1) chert, (2) volcanics (many of these being altered and albitized basalt and some of them andesite--a few of these are hypersthene andesites), (3) sandstone, and (4) some granite and quartz diorite. Similar lithologic types are revealed in the gravel-rich sediments north of Cape Flattery. The heavy-mineral study shows that in much of the area the sediments have low percentages of heavy minerals, although opposite Grays Harbor at depths of 10-12 fm and Hoh River at 10-28 fm, heavy minerals are more abundant. The sediments off Cape Flattery, especially in the nearshore areas, have smaller percentages of orthopyroxene nd hornblende than do those farther south. Also, the proportions of hornblende, ilmenite, and magnetite generally are less in the present study area than in the sediments opposite Columbia River. These results suggest that many of the gravel sediments (of the offshore areas), representing the glacial drifts, and the heavy-mineral-rich sediments were deposited at sea levels lower than at present. The drift toward the north of the Columbia-derived sediment appears not to have diluted considerably the sediments supplied from other sources to the areas farther north of Grays Harbor.

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