Chronological Biostratigraphical Classification of the Lower Tertiary
Published:January 01, 1959
In order to establish a standard chronologic biostratigraphic section for the Lower Tertiary of California certain requirements must be met. The sequence should, for the interval under consideration, be:
under demonstrable superpositional control
a continuous and uninterrupted lithologic sequence
paleontologically controlled at both bottom and top (recognizable and definable paleontological criteria at base and top)
The difficulties involved in fulfilling all of the above requirements are immediately apparent. Indeed, the ideal sequence probably does not exist. An attempt has been made in this report to approximate as closely as possible the ideal.
The first sequence of Lower Tertiary strata studied by the writer was that exposed in the vicinity of Media Agua Creek in the Temblor Range on the west side of the San Joaquin Valley in Kern County, California. Some 2,300 feet of marine Lower Tertiary strata exposed here are assigned to the Lodo and overlying Tejon formations (see Figs. 1, 2, 3). Most of this sequence is highly foraminiferal (see Table 1). An analysis of the microfossils in the light of related data from other sources indicates that ( 1 ) the Lodo formation of this section was laid down at depths varying between the littoral district and the edge of the continental shelf, in a sea with tropical or subtropical surface temperatures, and with open ocean connections prevalent during most of its deposition; (2) that the overlying Point of Rocks member of the Tejon formation was
Figures & Tables
Lower Tertiary Biostratigraphy of the California Coast Ranges
As a result of field work carried on in 1947 a sequence of foraminiferal samples were collected in 2,300 feet of Lower Tertiary mudstones, siltstones, and interbedded shales and sandstones in the vicinity of Media Agua Creek, in the Temblor Range on the west side of the San Joaquin Valley.
Foraminiferal samples from another less comprehensive sequence of Lower Tertiary strata were collected during the years 1947, 1948, and 1949 in the region of Devils Den.
The prepared samples were studied during the years 1947–1952 in the Department of Paleontology at the University of California under the direction of Dr. Robert M. Kleinpell. Subsequent work both in the field and laboratory has been directed toward obtaining as complete and chronologically diagnostic a faunal sequence throughout the Lower Tertiary in the California province as possible.
Preliminary results of certain phases of the investigation have been presented from time to time at meetings of the Pacific Section of the American Association of Petroleum Geologists, San Joaquin Valley Geological Society, Cordilleran Section of the Geological Society of America, and the Northwest Geological Society (Mallory and Boyd, 1949; Mallory, 1953a, 1953b, 1954a, 1954b). This paper attempts a synthesis and revision of these reports and their conclusions, and the incorporation of many new data.
The majority of species known to be important in the Paleogene foraminiferal faunas are figured and their stratigraphic distribution in the California province is noted. In addition, an attempt has been made to draw any inferences from all kinds of fossil