528 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Introduction and Acknowledgments 



The geology of the southern half of California and that 

 of the Sierra Nevada has been largely elucidated because 

 the occurrence of those great sources of California's mineral 

 wealth, Oil and Gold. Owing to the lack of such an eco- 

 nomic inducement, geological research and mapping in the 

 northern half of the Coast Ranges has been largely neglected. 

 The writer became interested through work in the southern 

 half of the state in certain problems whose solution re- 

 quired detailed mapping in the northern half. Some interest- 

 ing and unexpected results were obtained through an exten- 

 sion of the work of Professor Lawson in the San Francisco 

 Quadrangle, and that of Dr. Weaver in the Napa Quad- 

 rangle, east of the area studied. The excellent topographic 

 maps of the Petaluma and Santa Rosa quadrangles were 

 available during most of the time the writer was engaged in 

 this research. The Point Reyes Quadrangle was not avail- 

 able during the field work. It is hoped that the rapid pub- 

 lication of suitable topographic maps will lead to more work 

 in this much neglected field. 



The writer is aware of the incompleteness and many de- 

 ficiencies of this work, but it was thought best to present the 

 results obtained at this time so that they may be available for 

 use by others. 



For helpful criticism, the writer is greatly indebted to Pro- 

 fessors Andrew C. Lawson, John C. Merriam, Ruliff S. Hol- 

 way, Bruce Clark, and Chester Stock of the University 

 of California; Professor James Perrin Smith of Stanford 

 University; Professor Earl L. Packard of the University of 

 Oregon ; Dr. W. S. W. Kew of the U. S. Geological Survey ; 

 and to Mr. John B. Kerr, Geologist, General Petroleum Com- 

 pany, who assisted in the field work during the summer of 

 1916. The writer is also under great obligations to Mr. H. 

 C. Bundy, who prepared the geological sections, and to Mr. 

 L. L. Stewart who drew the manuscript copy of the geo- 

 logical maps. The California Academy of Sciences provided 

 the facilities for this work and the paleontological collections 

 upon which it is based are deposited in that institution. 



The mapping of the Petaluma Quadrangle and the south- 

 ern half of the Santa Rosa Quadrangle is detailed as respects 



