NO. I ABRUPT APPEARANCE OF THE CAMBRIAN FAUNA J 



In Speaking of the terrestrial formations of the Eocene, Chamber- 

 lin and Salisbury [1906, Vol. 3, p. 204], when comparing- the sedi- 

 mentation of the Eocene with the present time, say : 



Then as now, temporary and permanent streams were doubtless aggrading 

 their valleys, and building fans and alluvial plains where the appropriate 

 conditions were found, while sheet-floods spread debris washed down from 

 the higher lands on the tracts below. The deformative movements which 

 initiated the modern era probably gave rise to basins here and there, in which 

 lakes were formed, and the flows of lava from the unnumbered vents of the 

 time doubtless sometimes obstructed valleys, ponding the streams and giving 

 rise to lakes. Under these conditions, it is probable that much of the debris 

 which was started seaward by the swift waters of the higher lands found 

 lodgment long before it reached the sea, some of it at the bases of steep 

 slopes, some of it on river plains, and some of it in lakes. The wind also 

 made its contribution. The result was an inextricable combination of fluvial, 

 pluvial, eolian, and lacustral deposits. 



Terrestrial formations of Eocene age and of fluvial, pluvial, lacustral, and 

 eolian origin are widespread throughout the western interior, occurring even 

 in proximity to the western coast. Many of them are of limited extent, 

 while others are spread over great areas. 



Again, in describing the terrestrial deposits of the Miocene, the 

 above authors say [p. 266] : 



The terrestrial Miocene formations (the Truckee Miocene^ of King) are 

 said to reach a thickness of 4,000 feet (King) at some points in the vicinity 

 of the 40th parallel. In general, they are made up of sandstones, con- 

 glomerates, volcanic debris, infusorial earths, and fresh-water limestones, 

 overlain by great thicknesses of volcanic tuffs. The John Day series, the 

 upper portion of which is perhaps Miocene, is also thick (said to be 3,000 or 

 4,000 feet), and is made up largely of volcanic ash and sand, much of which 

 seems to be eolian.* 



Other areas of deposition, some of them lakes, existed during the Miocene 

 in Nevada and Montana. In the southwestern part of Nevada, the Miocene 

 beds (Esmeralda formation) described as lacustrine, consist of the usual 

 sorts of clastic rocks, pyroclastic material, and workable coal, the latter 

 showing that the formation is not altogether lacustrine. The formation also 

 carries some sulphur. The remarkable thickness of 14,800 feet (which may 

 include Pliocene beds) is reported for this formation." 



Tn the fresh-water Morrison formation of Colorado Mr. Darton 

 notes the presence of 66 feet of limestone [Darton, N. H., 1905, p. 

 97] in a section 166 feet in thickness. 



' King, Geol. Expl. of the 40th Parallel, Vol. i, pp. 412, 458. 



" Merriam, Journ. Geol., Vol. g, p. 71, and Bull. Dept. Geol., Univ. of Cal., 

 Vol. 2, p. 306. 



' Turner, Amer. Geol., Vol. 29, p. 268, and 21st Ann. Rept. U. S. Geol. 

 Survey, Pt. 2. 



