142 University of California Publications in Geology [Vol. 9 



shales and lenses of carbonaceous shales, interstratified in places with 

 seams of coal of an inferior quality. 



The most complete section of the Chico group was obtained along 

 the divide between Santiago and Aliso canons, the details of which 

 are given below. This section in descending order follows. 



Section op the Cretaceous Along the Santiago-Aliso Divide 



Description of the Lithology 

 Fine-grained, calcareous, tan shales 



Covered by Vaqueros 

 Tan sandstone intercalated with a resistant, 



laminated, micaceous, gray, sandstone 

 Hard, gray, micaceous sandstone 

 Brownish-gray, sandy shales 

 Coarse white sandstone, with a few rounded 



pebbles 



Light-colored conglomerate, alternating with 

 bands of gray sandy shale, weathering to 

 a dark red 



Fine-grained, steel-gray shale with lenses of 



calcareous sandstone 

 Fine-grained gray shale with calcareous nodules 

 Laminated sandstone, slightly conglomeratic, 



interbedded with gray shale 

 Gray, conglomeratic sandstone 

 Heavy, gray conglomerates 



Total thickness of the Chico group 

 Trabuco formation 



Red conglomerates with subordinate bands of 

 red sandstone 



Total thickness of the Chico and the 

 Trabuco 



Faunal Zones 



Teilina ooides zone 



Turritella pescader- 

 oensis zone 



Actaeonella ovifor- 

 mis zone 



Estimated 

 Thickness 



65 feet 

 120 



130 



45 

 140 



60 



200 



125 

 550 



50 

 100 

 200 

 1600 



200 

 1800 



Fauna 



general character 



The Cretaceous fauna recently obtained from the Santa Ana Mount- 

 ains includes eighty species and varieties of Pelecypoda, thirty-three 

 of Gastropoda, eleven of Cephalopoda, one of Seaphopoda, besides a 

 few specimens belonging to the Molluscoidea, Vermes, Echinodermata; 

 Arthropoda and Vertebrata. The entire fauna comprises one hundred 

 and thirty-one forms, of which twenty-two are new. The fauna from 

 this region is further increased by other workers who obtained in the 

 same field a number of species not recognized in our collections. 



