The Geology of San Nicolas Island, California: ABSTRACT
The rocks forming San Nicolas Island are almost wholly composed of sandstones and shales, Middle Eocene in age. The island is elongate, with its major axis running N. 70° W. The submarine contours reflect a similar trend in a much larger mass and further indicate a rather extended uplift in a northwest direction toward Santa Rosa Island. San Nicolas Island is a high point on this uplift and the attitudes of the sedimentary series suggest that the island is the southeast end of an eroded and faulted anticline, with the anticlinal axis about one mile landward along the southwest shore, trending roughly northwest. The topography is in harmony with the folding, and the shape of the island is guided by the structure of the underlying sedimentary rocks. Five marine terrace above the one now being abraded show the successive stages in the carving of the island. The folding and faulting antedate the terracing, for the marine terraces cut across the beds disregarding structure. The terrace surfaces are not perceptibly warped and are nearly parallel to one another. End_of_Article - Last_Page 1519------------