University of California publications. Bulletin of the Department of Geological Sciences Volume 9

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...will indicate the approximate relation between any two formations: that is, if the combined percentages of the species common to A and B is greater than the combined percentages of the species common to B and C, it will indicate that A and B are more closely related than B and C. There are a few sources of error which will affect the results very greatly unless they are eliminated. A small number of species from one formation will change the factors considerably. It is necessary therefore to have a large number of species from all of the formations which are to be considered. Geographical separation also affects the results very noticeably. Formations that are widely separated will have a smaller number of species in common than formations that are not so situated. With our data tabulated as in the following tables, and with the possibility of errors in mind, we can readily construct a correlation table which will show the relations of each formation as worked out by the percentage method. Turning to table 3 we find in the first column, reading from top to bottom, the percentage of living forms. The formation having the greater per cent of living species will, of course, be the most recent. Those having the same percentage of living forms will be approximately contemporaneous in deposition. Considering then the percentage of living species we find that the upper Merced is very recent, certainly Pleistocene. The Merced of Bolinas Bay, of Afio Nuevo Bay, of Seven Mile Beach, of Pillar Point, and of Sargent Oil Field are all of the same-age and are very closely related to the upper Wildcat and to the Purisima. The Etchegoin of the Sargent Oil Field, the lower Wildcat, and the so called Miocene of Bear River are older. Taking now the factors representing the pe...