226 JAMES PERRIN SMITH 



the Triassic of the Great Basin region, with only four thousand feet 

 of calcareous sediments, probably represents at least one-third longer 

 time than the Cretaceous of California, with its thirty thousand feet 

 of sandy beds. The Tertiary formations of California, which are 

 about fifteen thousand feet thick, represent about one-half the time 

 of the Cretaceous, which is twice as thick, and about one-third of the 

 time of the Triassic of this region, which is hardly one-fourth as thick. 

 The other formations are too incompletely developed here, or too 

 varied in composition, for any reliable estimate of their relative length 

 of time to be made. The Carboniferous section is complete, but has 

 sandstones, shales, limestones, and tuffs alternating in such a manner 

 that, with our present knowledge, it is hardly possible to estimate the 

 entire system in terms of limestone. 



NEOCENE FORMATIONS OF CALIFORNIA 



Because of the numerous formations that have been named in 

 the Tertiary of California, and the numerous changes that have 

 recently been made in the nomenclature and succession of these 

 formations, a detailed table is here added, for the sake of those inter- 

 ested in West Coast geology, and not familiar with its details. 



The great development of petroleum in California and the intense 

 activity of geologists in that field are responsible for the embarrassing 

 wealth of formational names in the Neocene. They are necessary, 

 at present, for it is a difficult matter to correlate the minor horizons 

 with accuracy over such a large region. 



