68 



University of California Publications in Geology [Vol. S 



A short description of these same beds is also given in the Santa 

 Cruz folio :° 



The diabase exposed north of the headwaters of Peseadero Creek has 

 brought up some considerable inclusions of impure limestone which, from the 

 fossils found in them, appear to be of Eocene age. The limestone is light brown 

 in color, usually rather soft except where silicification has begun, and appears 

 to be made up of broken marine shells, a little argillaceous material, and small 

 fragments of what may be tuff. The thickness of the limestone is nowhere more 

 than 100 or 200 feet, 



On Langley and Mindego Hills, two and a half miles northeast and south- 

 east, respectively, of the village of La Honda, are two other small areas of 

 calcareous sandstone, supposed to be of the same age as that exposed north 

 of the headwaters of Peseadero Creek. 



Fossils — The fauna of the limestone in the Peseadero Creek exposure above 

 referred to is different from that of any of the other known formations of 

 California, Some of its species as Patella mateoensis Arnold, Fissurella perrini 

 Arnold, Tritonium newsomi Arnold, and Pecten proavus Arnold, are closely 

 allied to Chico (Cretaceous) forms, while Ostrea cf. idriaensis Gabb is found only 

 in the Tejon (middle Eocene), and Terebratulina tejonensis Stanton only in the 

 Martinez (lower Eocene). In view of the affinities of the above species and 

 also of the several new ones, it appears probable that the fauna represents 

 either a new horizon of the lower Eocene or a local development of the 

 Martinez (lower Eocene) fauna. 



These beds do not appear to be of Martinez age to the writer. 



Diekerson 1 " in a short paper described unconformities between the 

 Martinez and Chico and between the Tejon and Martinez, and gave 

 partial lists of fossils collected from a section across the strike from 

 the Chico, Martinez and Tejon. These lists show a very marked 

 difference between the faunas of the Chico, Martinez and Tejon. 



In a recent number of the Journal of Geology, Dumble 11 described 

 an unconformity between the Cretaceous and beds which he supposed 

 to be of Martinez age. Later work by Taff, Gester, Parsons, and 

 Diekerson has shown that the so-called Martinez is Tejon. 



s Branner J. C, Newsom, J. R., Arnold, R., Santa Cruz Polio, No. 165, U. S. 

 Geological Survey, p. 3, April, 1908. 



10 Diekerson, Roy E., The Stratigraphy and Faunal Relations of the Martinez 

 Formation to the Chico and Tejon North of Mount Diablo, Univ. Calif. Publ. 

 Bull. Dept. Geol., yobj, ppU73-177, 1911. 



11 Dumble, E. T., Notes on Tertiary Deposits near Coalihga Oil Field and 

 their Stratigraphic Relations with Upper Cretaceous, Jour. Geol., vol. 20, pp. 

 28-37, 1912. 



