Abstract

Nearly 1000 bottom samples from the shallow portions of the East China and South China seas were studied and compared with source areas and oceanographic conditions. Sediments of the Gulf of Pohai and central Yellow Sea are fine-grained, low in calcium carbonate, and contain many unstable minerals and a moderately high percentage of organic matter. Most are contributed by the Hwangho (which carries much eroded loess), Yangtze, and many smaller rivers. The thickness of these sediments is so great as to constitute a modern zeugogeosyncline.

Sediments on the inner half of the continental shelf between Shanghai and Hainan and in the Gulf of Tonkin are similar to those of the central Yellow Sea; they comprise modern detrital materials contributed to the continental shelf by many rivers, but in amounts as yet insufficient to cover the shelf everywhere. Seaward of these sediments, on the outer half of the continental shelf between Korea and Hainan, is a broad belt of coarse sandy sediment from which finer sediments are winnowed away or prevented from being deposited by the strong Kuroshio Current. The sediment contains glauconite and much calcium carbonate in the form of foraminiferal tests and broken mollusk shells but very little organic matter. Because the inorganic portion is much coarser than that nearer shore, it is believed to constitute a littoral deposit left from a Pleistocene time of glacially lowered sea level. Locally on the shelf small areas of residual sediment near rock outcrops commonly contain reworked fossils. Pieces of pumice and many small shards of volcanic glass are present in the sediments but nowhere are they abundant enough to form a dominantly volcanic sediment. The shelf sediments are similar in most respects to those on the continental shelf of California, and they clearly indicate deposition below present base levels of equilibrium.

Seaward of the continental shelf, in deep water of the continental slope, the sediments are finer-grained and contain more calcium carbonate. These sediments consist of the finer-grained terrigenous material that bypasses the shelf and is deposited so slowly in the quiet deep water that Foraminifera make up a large percentage of the total sediment.

First Page Preview

First page PDF preview
You do not currently have access to this article.