New Evidence for Occurrence of Debris Flow Deposits in the Deep Sea.

摘要

Clearly defined debris flow deposits generated by a large sediment slide or slides off the Spanish Sahara have been identified on the lower continental rise west of the Canary Islands. The debris flow traveled over a slope as low as 0.1 deg. and a distance of several hundred kilometres. The deposits cover an area of sea floor of about 30,000 sq km. Recognition of the debris flow deposits is based on a characteristic geometry, a distinctive acoustic character, a pebbly mudstone fabric and sharp angular contacts in piston cores, and an undulating surface morphology revealed by bottom photographs. Similar deposits are observed on the Amazon cone and the North American continental rise and in the Gulf of Mexico and the Mediterranean Sea. Debris flows are probably a much more important depositional process on the sea floor than was previously suspected. (Author)