ABSTRACT

A portion of the Cretaceous turbidite section of the Coast Ranges in central western California was sampled and studied to determine the relationship between the grain fabric of the sandstone beds and the trend of sole marks on the same beds. Statistically significant alignment of elongate grains was observed within 62 beds that exhibited sole marks. In six beds studied at multiple levels, the best grain alignment was observed in the lower middle portion of the beds. The position in these six beds that yielded the mean grain trend that was most closely parallel to the sole mark trend did not appear to be consistent or predictable by any criteria discovered to date.

It was further noted that the level in the beds that yielded the mean grain trend that was most nearly parallel to the sole mark trend was not always the level at which the best grain alignment was observed.

The mean grain trends at the different levels in the six beds studied at multiple levels tended to be grouped around the sole mark trend on each bed with about an equal number falling on either side of the sole mark.

In a statistical sense, out of a population of 62 sole mark bearing sandstone beds sampled at only one level or for which the data from multiple sample levels was averaged for the bed, a predictable relationship was observed to exist between the mean grain trend and sole mark trend.

In one sandstone bed studied at three levels, the current sense indicated by the dip direction of the imbricate grains in the middle and lower intervals is the same as that inferred froth the flute-casts on the base of the bed. The imbricate grains in the upper interval of the bed dip in the opposite direction from those in the lower intervals. Statistically significant data was obtained only from the lowest interval in the bed.

It is inferred that the deviation of sole mark trend from mean grain trend is observed in these beds because they are the turbid current deposits of a submarine fan. The observed deviations are probably due to divergences in the travel path of the trailing part from the leading part of each current.