236 



J. F. NEWSOM — CLASTIC DIKES 



in figure 1, while the relations of the dikes along the coast to those at 

 the asphalt quarries are shown in figure 4. 



GEOLOGIC RELATIONS OF THE DISTRICT 



The geologic relations are comparatively simple in the region near 

 Santa Cruz, in which the sandstone intrusions occur. The oldest rocks 

 in the district are the granites which form the core, and the eastern crest 



Diatomaceous 

 Shale (Miocene) 



Miocene(.?) 

 Sandstone 



Granite &nd 

 Mefamorphics 



P/iocene Area corereaf Ar-ea coyere<f 



Sandstone ^Sttal e by fig./\/o.lO. by ^/y. /Vo S- 



^ W^ l 



Figure 4:.— Geologic Map of the Santa Cruz Dike Region. 

 The sandstone intrusions occur west and northwest of Santa Cruz, California. 



of Ben Lomond mountain. Resting on the granite in some places are 

 schists, with overlying patches of metamorphosed limestones and quartz- 

 ites; at others the later sedimentaries, supposed to be of Miocene age, 

 lie directl}^ upon the Ben Lomond granite. 



The east face of Ben Lomond mountain forms an abrupt escarpment, 

 but to the west and south the mountain slopes gradually to the sea, and 

 on three sides it is flanked b}' sandstones and diatomaceous shales of 



