Abstract
Near-surface sediments on La Jolla Fan have been studied using over 100 cores, mostly 60 cm long box cores. Sediment distribution on the fan is apparently related to processes acting along the prominent fan valley, which cuts deeply into Pleistocene sediments. The Holocene sediments in the fan valley consist of sands with some interbedding muds; a few of these muds are in thin beds in which the low sand content is graded. All the other muds are bioturbated. On the open fan away from the fan valley, sands are thinner and rarer. In a 5 km 2 area on the lower fan, two sand layers have been correlated among ten cores. Sedimentary structures within the sands suggest they were deposited from relatively powerful currents, of gradually declining competence, carrying large amounts of sediment in suspension; these are thought to be turbidity currents. Much of the mud also appears to have been deposited from turbidity currents. The Holocene sediments on the fan are about 2 m thick, indicating that about 90% of the sediment being supplied to La Jolla Canyon is by-passing the fan.
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