by the tides. Closer to the island, the current meter data indicated 

 rotational water movement with a resultant vector to the southeast 

 and a speed of 9 cm/sec. 



Current meter data analysis indicated maximum clockwise rotation 

 at new and full moons. Drogues, however, had maximum tidal rotation 

 at the quarter moons which indicates that the drogues launched during 

 the quarter moons (those at sites 1, 2, and 4) were launched in areas 

 where localized eddies are formed by the tides. The drogues at sites 

 3 and 5 were launched when clockwise tidal rotation was at a maximum. 

 The tidal forces were overpowered by the counterclockwise flow around 

 the basin. Therefore, the speed of water flow around the periphery 

 of the basin precludes the formation of tidal eddies. This result 

 may not be true at the center of the basin where water speeds are 

 not as great. 



F. Bottom Composition. 



1. Core Analysis . The area encompassed by this survey lies 

 within the block-fault complex of deep basins and intervening sills, 

 ridges, and banks that forms the sea floor off the southern California 

 coast. As a result of concentrated work in this area over the past 

 20 years, the general characteristics of the bottom sediments are 

 fairly well known. A comprehensive presentation of these characteristics 

 and their significance is given by Emery (1960) . 



Basically, the sedimentary pattern is one of fine-grained sediments 

 (chiefly silty clays) in the depressions and somewhat coarser material 

 on the elevations. This basic pattern is presented only as a generaliza- 

 tion, however, and variations may and do occur owing to several factors, 

 the dominant of which is the mass downslope movement of sediment . 



Sediments are supplied to the area from a variety of sources. 

 Planktonic organisms, primarily foraminif era, are important contributors, 

 and their importance increases with distance from shore. Fine terrigenous 

 material is carried from the adjacent coast to the area by aerial 

 and aqueous suspension. Subaerial erosion of exposed ridge tops 

 (San Nicolas and Santa Barbara Islands) affords a proximate source 

 of present day coarse and fine clastic detritus as did erosion of 

 the more extensive ridges and banks during lower stages of sea level. 

 Benthic organisms on shallow banks, island shelves, and ridges contribute 

 abundant material, chiefly in the form of carbonate debris. Chemical 

 precipitates, notably glauconite and phosphorite, may be important 

 and even the dominant constituents on bank tops and ridge crests. 



Sediment cores collected in the course of this survey (Fig. 2) 

 generally support the known pattern. Samples from the Santa Cruz 

 Basin (cores 2, 3, and 4), the San Nicolas Basin (cores 7, 8, 12, 

 13, 14, 15, 16, and 18; and grabs 9 and 10), and the Tanner Basin 

 (core 17) were dominantly fine-grained, green-gray muds with rather 



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