Fauna of the Merychippus Zone, North Coalinga District, California. The Structural Geology of the San Joaquin Hills, Orange County, California

[Major thesis] Fauna of the Merychippus zone, north Coalinga district, California: The Merychippus zone occurs at the top of the Temblor sandstones on Domengine Creek, twelve miles north of Coalinga, California. The fauna includes a significant representation of ungulates and carnivores, with the Equidae far outnumbering all other forms. The stratigraphic position of the Merychippus zone in the Tertiary marine series, exposed on the west side of the San Joaquin Valley, lies within a zone whose assignment either to the middle Miocene Temblor or the upper Miocene Monterey is at present disputed among geologists familiar with the area. That its position is close to the dividing line between Temblor and Monterey is deemed significant for this report. In its stage of evolution and in its relationships with Tertiary assemblages of the Great Basin Province, the fauna of the Merychippus zone occupies a position intermediate between the middle Miocene Mascall of eastern Oregon and the upper Miocene Barstow of the Mohave Desert. A study of the occurrence of the material leads to the conclusion that the accumulation of fossil remains took place in the forest portion of a delta of a large river, where remains of land mammals were mingled with those of marine vertebrates. The suggestion is made that during the period of accumulation of the deposits and of the organic remains, the land area contributing this material was one of low relief and characterized by a rainfall of approximately 30 inches. The fauna is described in detail. [Minor thesis] The structural geology of the San Joaquin Hills, Orange County, California: A study of the geology of the San Joaquin Hills, southeastern Orange County, was undertaken originally, in collaboration with Mr. W. A. Findlay, as a research problem to be completed in fulfillment of the requirements for the degree of Bachelor of Science at the California Institute of Technology. The original investigation served mainly to arouse an interest in the problem for Mr. Findlay and the writer. In May, 1932, Mr. Findlay submitted a report on the general areal geology of the area as a thesis for the degree of Master of Science. It was then decided that mapping should be continued in the area in detail, with Mr. Findlay devoting time to a preparation of a thesis on the sedimentary petrography and the writer continuing his study of the structural geology. This paper presents the results of the structural investigation and is submitted as a minor thesis in partial fulfillment of the requirements for the degree of Doctor of Philosophy.