70 



University of California Publications. 



[Geology 



Chittenden section. The stratigraphic relations of the Santa 

 Margarita formation will doubtless in time be more satisfactorily 

 determined and the brief mention of the occurrences in this 

 region may point out a favorable field for investigation. 



MEECED AND PUEISIMA FOEMATIONS. 



In the Pajaro Valley region a thick series of marine beds 

 lies unconformably over the San Pablo formation. The actual 

 contacts between these two formations are obscure and doubtful. 

 That these beds, here called Merced and Purisima, overlie the 

 San Pablo is evident and discordance of strike and dip point 

 toward a marked unconformity. These beds overlie uncon- 

 formably the Monterey shales over large areas and this fact 

 points towards a large erosion interval between San Pablo 

 and Merced time. 



The Purisima and Merced formations are not here separated. 

 They form a conformable series wherever noted in this part of 

 the State, and their separation is not a simple problem, especially 

 in the Pajaro Valley region, where the areas of these rocks are 

 devoid of outcrop and where railroad cuts form almost the 

 only means of detailed study in the field. By means of squirrel 

 burrows and soil it is not usually difficult to outline the areas 

 of these rocks. 



The formation is about 1500 feet thick and it is therefore 

 probable that only a part of the total Merced is present. The 

 Pajaro Valley is practically sculptured in Merced rocks. These 

 beds form a belt passing from the lower Pajaro and Salinas 

 valleys across the diorite and along the upper Pajaro Valley 

 to where the river of that name turns northeast. The surface of 

 the diorite just south of the Pajaro River has been exposed by 

 hydraulicking and here the Merced beds, composed of very 

 fossiliferous friable sands and gravels, are well exposed. In the 

 railroad cut just east of Chittenden there is another good 

 exposure. That the Merced beds pass over the diorite and into 

 the upper Pajaro Valley is certain. The uppermost surface 

 of the diorite is well water-worn, and the crevices of the rocks 

 are filled with sand and fossil remains ; and foreign water-worn 

 material is scattered over the ground on the highest points of 



