80 University of California Publications in Geology [VOL. 8 



On the eastern flank of the syncline, beds of Martinez age are represented 

 immediately west of Bull's Head Point, and south of this point they appear 

 east of the road leading from Pacheco to Martinez. These, together with the 

 Chico and Tejon, dip steeply to the southwest. The strike of these beds carries 

 them across the Strait of Carquinez, where they again outcrop just north of 

 Army Point Station. At this point the formation was so thickly bedded that 

 it was difficult to obtain accurate observations of the dip. Apparently, however, 

 they dip at high angles to the southwest. In this locality the outcrops are 

 separated from both Chico and Tejon by low marshes, so that no actual contact 

 could be observed. However, no marked irregularity in the dip was seen. The 

 strike of these beds was traced to a point about three miles northwest of 

 Benicia. Farther than this no outcrops were seen which could definitely be 

 called Martinez. To the west of Benicia thick-bedded sandstones closely 

 resembling those at Army Point were observed dipping steeply to the north- 

 east. Farther west the Chico again occurs, dipping at the same angle as the 

 thick-bedded sandstones, but near the shore it is folded and again dips to the 

 southwest. The strike and dip of these beds where carried across the straits 

 are almost identical with those south and west of Martinez. The most reasonable 

 conclusion would seem to be that there exists here a closely folded syncline. 



The structure of the Martinez to the south and west of the town 

 of Martinez is not as simple as Weaver's description implies. Basal 

 beds of the Martinez with their associated fauna such as have been 

 described above in the Martinez area north of Mount Diablo have not 

 been recognized with certainty, but the Trochocyathus zitteli zone is 

 very thick in the southeastern portion of the Martinez between Canada 

 del Hambre and Ignacio Valley, a distance of three miles. On the 

 southwest of this area, the Martinez is in contact with the Monterey. 

 Just what relation exists between the two is very difficult to discover. 

 No Tejon appears to be present along this line, but near the town of 

 Walnut Creek the continuation of the Monterey strata is in contact 

 with the Tejon, so we are inclined to think that the Monterey has 

 overlapped the Tejon and a part of the Martinez, and lies upon both 

 unconformably. Outcrops are infrequent along the contact and are 

 in general too poor to give any decisive evidence. The dips of the 

 Martinez in this area are all to the northeast. The area, however, is 

 twice as wide as the distance between the Chico and Tejon at Muir 

 Station. The northward extension of this area consists of two strips 

 of Martinez with a tongue of Chico between. The southern strip runs 

 northward for three miles to Alhambra Springs. Here it is cut off 

 by a thrust fault, which runs northward to Carquinez Strait, where 

 Martinez again occurs at the Selby Smelter. 



