GEOLOGIC RECONNAISSANCE IN BAJA CALIFORNIA 727 
CHICO FORMATION 
The upper part of the Chico formation (late Cretace ous) rises 
above sea-level a few miles north of Rosario, and it remains in view 
along the ocean bluffs and lower parts of the valleys of the Rio 
Rosario, Arroyo San Vicente, Rio San Fernando, and Arroyo Santa 
Caterina as far as latitude 29° 24’, a few miles southeast of Punta 
Canoas. ‘The rocks are soft sandstone and shale of light-gray to buff 
color with round concretions at most places. Emmons and Merrill* 
noted the occurrence of Upper Cretaceous fossils at a point about 
3 miles north of Santa Caterina Landing. Specimens collected from 
massive sandstone near sea-level and in calcareous layers 200 teet 
above were determined by T. W. Stanton as follows: Arca breweriana 
Gabb; Baculites chicoensis Trask; Tessarolax distorta Gabb; and 
Inocerami, not determinable. 
Fic. 7.—Fossiliferous Cretaceous sandstone northeast of San Fernando Mission, 
twenty miles east of San Rosario, Baja California. 
The fossils which I obtained in these beds at the Arroyo Hondo, 
15 miles north of Rosario, were identified by Dr. T. W. Stanton as 
follows: Ryhnchonella sp.; Ostrea sp.; Inoceramus whitneyt Gabb; 
Yoldia nasuta; Nemodon vancouverensis Meek?; Dentalium sp.; 
Gyrodes sp.. Anchura sp.: Cinulia obliqua Gabb; Baculttes chicoensis 
Trask; and Baculites occidentalis Meek. All these fossils are typical 
of the Pacific Coast Chico which is of Upper Cretaceous age. 
Lindgren? has reported the occurrence of the Chico fossil, 
Coralliochama orcutti, in sandstones appearing in a small area among 
the volcanic rocks a few miles southwest of Ensenada. 
= Op. cit., Pp. 501. 
2 Op. cit., p. 176. 
