July 28, 1910] 



NATURE 



RECENT WORK OF GEOLOGICAL SURVEY^.- 



IV. — The United States. 

 "T^HE United States Geological Survey frequently assists 

 research by publications in which definite subjects 

 are dealt with Irniii a comprehensive point of view. The 

 Bibliography of North American Geology for 1906 and 

 1907 was issued in 1909. A bibliography of Arch;ean and 

 Algonkian geology, divided up under the various States, is 

 given in Bulletin 300 (pp. 940, 1909), in which Messrs. 



Van Hise and Leith review the pre-Cambrian geology of 

 North America. As the title shows, Canada is included, 

 and the summaries given of published work make this 

 volume welcome in every library of scientific reference. 

 Bulletin 364 {1909) is by Messrs. Darton and Siebenthal 

 on the Laramie basin in south-eastern Wyoming. The 

 name Casper formation is proposed (p. 13) for Carbon- 

 iferous limestones and sandstones resting on pre-Cambrian 

 rocks on both sides of the Laramie Range. The Laramie 

 beds, over which much discussion has arisen, may be re- 

 presented by the highest sandstones and shales of the 

 Cretaceous Montana series, and an unconformity, now 

 widely recognised, occurs between this series and the 

 Cainozoic beds (pp. 35 and 43). The Laramie question, 

 it may be observed, has been recently discussed by Mr. 

 Whitman Cross (Proc. Washington Acad. Sci., vol. xi., 

 1909, p. 27), who proposes the name Shoshone Group for 

 the beds elsewhere styled Laramie, but lying above the 

 unconformity. The coloured geological map in the memoir, 

 and the illustrations, show well the character of the broad 

 valley of the Laramie, with its floor 7000 feet or more 

 above the sea, and gneissic hills rising some 3000 feet 

 higher on the east and west (Fig. i). Interesting contrasts 

 are afforded in a great variety of strata, especially Where 

 Oligocene sands form level ground in hollows of the 

 Archaean rocks of the Laramie range. 



Mr. D. F. MacDonald, in Bulletin 384, carries us up 

 to the old rocks of the Canadian border in the extreme 

 north of Idaho, where a large series of strata exist that 

 are presumably of pre-Cambrian age. Mr. J. S. Diller 

 (Bulletin 353) describes the Taylorsville region at the north 

 end of the Sierra Nevada in California, and to the south- 

 east of the great cone of Shasta. Compression of the 

 Jurassic and older sediments occurred here in early 

 Cretaceous times ; the present Sierra region began to rise, 

 and the Great Basin slipped away from it along faults 

 (p. 108). Though the sea, as happened in so many 

 other areas, returned during the Upper Cretaceous epoch, 

 it did not dominate the new mountains; soon after, it 

 became excluded altogether. Elevation continued in the 

 Eocene, and gold-bearing gravels streamed down until 

 the end of the Pliocene, when great warping took place, 

 accompanied by faulting. Hence (p. no) interesting 

 changes in the drainage-lines occurred, and old valley- 

 floors are traceable that undulate up and down, with bulges 

 ' Continued fiom v, 1. Ivxxiii., p. 234, April 21. 



NO. 2126, VOL. 8d] 



rising 1000 feet high across the former courses of the 

 streams. In describing the volcanic rocks, which are of 

 various ages, from Silurian to Pliocene, the author uses 

 the terms meta-rhyolite and meta-andesite for types much 

 altered from their original condition (p. 81). The famous 

 Lassen Peak volcano lies a little outside the area now 

 described. 



Mr. W. T. Lee (Bulletin 352) has explored a part of 

 western .Arizona, where the Colorado River emerges from 

 the Grand Canyon and runs southward, forming the State 

 boundary. Fine examples of consoli- 

 dated, and probably Quaternary, con- 

 glomerates and gravels, weathered out 

 into huge bluffs, are given in the 

 plates. The author describes the 

 erosion of valleys that went on in 

 Cainozoic time (p. 58), accompanied by 

 faulting ; then followed the great uplift 

 of the plateau, and renewed excavation 

 by the streams, the Colorado being now 

 driven to carve out the Grand Canyon. 

 The gravel deposits in the broad 

 Detrital-Sacramento valley to the south 

 are 2000 feet thick, and are believed to 

 have been deposited after the erosion of 

 the canyon. The obstacle that checked 

 the southward flow of the river down 

 this valley may have been a barrier of 

 comparatively modern basalt, and the 

 formation of a nearly fiat cone of de- 

 position above it allowed the river to 

 wander westward and to start new 

 excavation along its present course (p. 

 65). During this next epoch the 

 alluvial conglomerates were eroded into 

 their present fantastic outlines (Fig. 2). The history 

 of the southern valleys, here somewhat modestly pre- 

 sented, must clearly be taken into consideration when we 

 review that of the more famous plateau -region to the 

 north. The coloured geological map, inserted, according 

 to the present useful practice, in the memoir, enables one 

 to follow the arguments, as well as the travels, of the 

 author. It will be noted that the excavation of the Grand 

 Canyon is here transferred from Cainozoic to early 

 Quaternary times. 



Cambrian hills. 



2. — bluff of eroded Qua'ernary Conglo 

 Virgin River, .'\rizona. 



Mr. Lee also describes the " Manzano Group " of marine 

 red sediments in the Rio Grande Valley of New Mexico 

 (Bulletin 389, 1909). .Mr. G. H. Girty deals with the 

 palaeontology of these strata, which are now ascribed to 

 the Upper Carboniferous (p. 38). Red beds were deposited 

 in the Rocky Mountain region from Lower Carboniferous 

 to Jurassic times. There seems here a suggestion of the 

 continuity of the bright colour conditions that influence 

 tiopical and semi-tropical strata at the present day. The 



