Abstract

Mean orientations of elongate grains in thin sections of 62 samples from Cretaceous turbidite beds in central western California agree within statistically significant limits with the orientations of the basal sole marks of the respective beds. The high standard deviation of the means, 35 degrees , suggests that a large number of samples are required to determine the regional trend within reasonable confidence limits. Best alignment of grain elongation with sole marks is present in the lower middle portion of the beds. Orientation of dips of imbricated grains was measured in one bed at three levels; only dips at the basal level were in significant agreement with orientation of sole markings. Disagreement in imbrication orientations may be attributed to backwash, and variation in elongate grain orientations to changes in shape and velocity of the body of sediment as it was transported by the turbidity current.

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