310 GEOLOGY. 



the Miocene, and on the older formations as well, at various points 

 along the western borders of the Pacific states. In no case do the 

 marine Pliocene beds extend far inland, though Pliocene beds con- 

 taining marine diatoms are said to have been indentified in southern 

 Arizona up to elevations of nearly 4000 feet. 1 During the Pliocene 

 submergence, it has been thought that the islands of southern Cali- 

 fornia stood some 1500 feet lower than now. 2 The thickest Pliocene 

 beds of the continent, so far as known, are in the peninsula of San 

 Francisco, where the Merced series (perhaps partly Quaternary, 3 and 

 not all marine, as lignite shows) attains a thickness of more than 5800 

 feet, 4 and in the Santa Clara valley where the thickness of Upper Plio- 

 cene (partly fluviatile) is said to be 8000 feet. 5 Recently, a series of 

 beds below the Merced series, aggregating more than 7000 feet in 

 thickness and composed largely of volcanic debris, has been assigned 

 to the Pliocene. 6 If this be correct, it gives the Pliocene of the Coast 

 range near San Francisco bay a thickness of some 13,000 feet. In 

 the San Luis Obispo region there are late Miocene or Pliocene for- 

 mations (Santa Margarita and Pisma, shale, sandstone, conglomerate, 

 etc.), of 4500 feet (maximum) thickness, overlain unconformably by 

 Pliocene beds (Paso Robles) of non-marine origin, 1000 feet in thick- 

 ness 7 (Fig. 444). Other names (San Diego 8 and Wildcat, 9 Cal., 

 and Mytilus, 10 Ore.) have been applied to the marine Pliocene beds 

 of various localities on the Pacific coast. 11 To some of these, as the 



1 Blake, Sci., Vol. 15, p. 413, and Dumble, Jour. Inst. Min. Engineers, Vol. 31, 

 p. 696. 



2 Smith, Bull. Department Geol. Univ. of Cal., Vol. II. Reviewed in Jour. Geol., 

 Vol. VIII, p. 780. 



3 The Messrs. Arnold, Jour, of Geol., Vol. X, pp. 117-138. 



4 Lawson, Bull. Dept. Geol. Univ. of Cal., Vol. I, No. IV, p. 115 et seq. The upper 

 parts of the Merced of Lawson is put in the Pleistocene by Ashley, Proc. Cal. Acad. 

 Sci., 2d Ser., Vol. V, pp. 312-37, and the Messrs. Arnold, Jour, of Geol., Vol. X, p. 135. 



5 Hershey, Am. Geol., Vol. 29, pp. 359-70. 



6 Lawson, Science, Vol. XV, p. 410, 1902. The correlation of the beds between 

 the Monterey below and the Merced above, is not given in the publication. The 

 opinion that they are Pliocene is expressed by the author in a letter 



7 Fairbanks, San Luis, folio, U. S. Geol. Surv. 



8 The Messrs. Arnold, Jour, of Geol., Vol. X, p. 129, and.Dall, Proc. Cal. Acad. 

 Nat. Sci., Vol. VI, 1874. 



9 Lawson, Bull. Dept. of Geol. Univ. of Cal., Vol. I, p.- 255 and Ashley, Proc. Cal. 

 Acad. Nat. Sci., 2d series, Vol. V, 1895, pp. 312-331. 



10 Condon, Am. Nat., Vol. XIV, 1880, p. 457, and Dall, Bull. U. S. Geol. Surv. 



11 A good review of the Pliocene and Pleistocene of southern California is given 

 by the Messrs. Arnold, Jour. Geol., Vol. X, pp. 117-38. 



