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The AAPG/Datapages Combined Publications Database
The presence of strong bottom currents in the northern Channel Island passages makes these areas ideal for the study of sediment dispersion and energy regimes by analysis of the textural properties of the sediments.
A grid-sampling system was used to take 25, 36, and 37 grab samples from San Miguel Passage, Santa Cruz Channel, and Anacapa Passage, respectively. The sand fraction of each sample was analyzed texturally by an automatic settling tube. The data then were synthesized by an IBM 360 computer, which constructed 5th-degree trend surface maps for the mean, sorting, skewness, and kurtosis values for each of the passages.
Of the primary agents available for transport of traction load, it is suggested that wind-driven currents are more important in accounting for the sediment distribution than either tidal currents or wave action. Although the last two are active continually, it is believed that their effect is superimposed on the net movement caused by wind-driven currents, and hence they are subordinate processes.
San Miguel Passage is characterized by southeastward sediment dispersion. The energy level is highest in the center of the passage and there is a gradual decrease in energy toward the sides. A lobe of coarse sediment in the northern section of Santa Cruz Channel shows the southeastward dispersion; however, fine sediment from the east moves into the southern part of the area, where it is intercepted by currents at the head of Santa Cruz Canyon. Because there is dispersion both east and west, Santa Cruz Channel may represent a shear zone between two prominent currents. Anacapa Passage shows dominant westerly dispersion with a superimposed north-south tidal-current effect.
All the passages are believed to be at or near equilibrium with respect to sediments and mechanical energy.
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