Generalized sketch of Miocene stratigraphic section along southwestern margin of San Joaquin Valley: Supplement 2 from "Sources of Miocene sediments in southwestern San Joaquin Valley" (Thesis)

This investigation constitutes an attempt to determine by studies of heavy minerals, using a statistical approach, the sources of Miocene sands occurring along the southwestern border of San Joaquin Valley, and from a knowledge of these sources to deduce inferences regarding distribution of the sands and Miocene paleogeographic conditions. The method of attack chosen was to compare heavy mineral assemblages of the Miocene sands in question with those (1) of extant possible source areas and (2) of other post-Franciscan sediments the sources of which can be more readily inferred. The method used for sampling possible source areas was to sample fresh recent sands from streams draining these areas. Miocene samples were discreet "spot" samples. Considerable attention was given to development of laboratory and microscopic technique. The two items in this regard which are considered to represent most progress in technique are (1) use of ruled slides for grain counts, and (2) a method for use in centrifuge separations of heavy minerals. Effective methods of assembling and representing mineralogical results were devised