Correlation of organic shales in the southern end of the San Joaquin Valley, California

Correlation of the organic shales in the southern end of the San Joaquin Valley has much economic importance. Investigation of micro-organisms indicates that the upper 4,000 feet of this shale is equivalent to the shale at Monterey where early Miocene sediments are lacking. Local variations in these deposits make stratigraphic subdivisions of general application very difficult but microscopic fossils appear to afford a basis for recognition of different parts of the shale body.