THE PLIOCENE PERIOD 835 



are local, doubtfully consistent with one another, and better ex- 

 plained in some other way than by the operation of waves. 



Marine Pliocene Beds 



The Atlantic coast. If fossils be the test, Pliocene beds of 

 marine origin have little development on the eastern side of the 

 continent. In Florida only (Caloosahatchie beds) 1 have beds 

 containing marine fossils any considerable extent at the surface, 

 though small patches are known farther north. 2 They may be 

 parts of a continuous formation, chiefly concealed. The time 

 relations of these marine Pliocene beds to the Lafayette are unde- 

 termined. Pliocene beds of marine origin have not been certainly 

 identified between Florida and Texas, but they cover considerable 

 areas farther south, as in Yucatan. 



The Pacific coast. 3 Sedimentation was in progress over less ex- 

 tensive areas along this coast than during the Miocene period. The 

 area of marine deposition especially was greatly restricted (Fig. 

 556. Compare Fig. 543). The marine deposits are chiefly of fine 

 clastic sediments, while the non-marine deposits contain more 

 coarse material. The maximum known thickness of the marine 

 Pliocene is found south of San Francisco, where about 4,000 feet 

 of strata (Merced series) are exposed. 4 The non-marine part of 

 the system (Paso Robles formation) is about three-fourths as thick 

 in the San Joaquin valley. 



Crustal Movements of the Pliocene 5 



The tendency to crustal movements, both warping and faulting, 

 which had characterized the western part of the continent since 

 the close of the Mesozoic, seems to have continued at least inter- 



1 Ball, Am. Jour. Sci., Vol. XXXIV, 1887, p. 161, Wagner Free Inst. of 

 Science, Vol. XIV, pt. VI, p. 1604, Bull. 74, U. S. Geol. Surv. 



2 Dall, Trans. Wagner Free Inst. of Sci., Vol. Ill, Pt. II, pp. 201-217, 1892. 



3 Arnold, Ralph, Jour. Geol., Vol. XVII. 



4 Lawson, Science, Vol. XV, 1902, p. 410, and Hershey, Am. Geol., 

 XXIX, p. 359, give the Pliocene of California greater thicknesses. 



5 LeConte, Am. Jour. Sci., Vol. XXXII, p. 167, 1886, Bull. Geol. Soc. Am., 

 Vol. II, p. 329, Jour. Geol., Vol. VII, p. 546, 1899; Hershey, Science, Vol. 

 Ill, p. 620, 1896; McGee, 12th Ann. Kept., U. S. Geol. Surv., and Science, 

 Vol. Ill, p. 796; also King, op. cit., and Button, Mono. I, U. S. Geol. Surv. 



