532 



Arnold Heim— 



25 





roc/OS So/7toMl\'::, 73 \V'-^v»v.vv? 



5," km 



J^ Jose 





//2 



/// 



C.S.Lucos 



//o 



Fig. 1.— Southern part of Lower Californian Peninsula, Mexico. + Fossils 

 of Lower and Middle Tertiary, x Fossils of Salada Formation, Pliocene. 

 * Volcanic cones. O Towns and villages. G. La Giganta Mountain, 

 1,765 metres. M. Magdalena Bay. S. La Salada rancho. T. ElTepetate 

 rancho. H. San Hilario oasis. L. Loreto. 



and more rapidly descending to the Gulf coast. The characteristic 

 form of surface is the table (Mesa) or high plateau. It is formed 

 by sedimentary and volcanic rocks of Tertiary and Quaternary 

 age. In this paper, special attention will only be given to the 

 Tertiary sediments of this Mesa Region. 



The exact age of some of the Tertiary formations being 



