500 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



BLACK MOUNTAINS 



DEATH VALLEY 

 FormerLohe Monty 



T5^.— 





A' 





ALEXANDER HILLS 



?p€btn*CU Qo€n AMAR605* TH pCp Qa 



— vg^qfe^g ' " ■ " iM i n . t. 11 ., i i mm i " 



Fig. 31.8 Cross section of the southern Death Valley region. After Noble (PI. 3, 1941). Tp, 

 Pliocene (?) fanglomerate; Tv, undifferentiated volcanic rock; £wc, Wood Canyon formation 

 (quartzite, shale, and fossiliferous limestone); Cs, Sterling quartzite; Cj, Johnnie formation 

 (quartzite, shale, and dolomite); Cn, Noonday dolomite; p€, earlier Precambrian basement 

 complex; p£k, Kingston Peak formation (conglomerate, quartzite, and shale); p€b. Beck Spring 

 dolomite; p€c, Crystal Spring formation (quartzite, shale, and dolomite). 



are granite, red Tertiary conglomerate, rhyolite, rhyolite tuff, porphy- 

 ritic andesite, quartz latite porphyry, gypsiferous shale, fresh-water lime- 

 stone and fanglomerate of Tertiary age, and various Precambrian and 

 Cambrian rocks. 



The Amargosa thrust and chaos are folded into several plunging anti- 

 clines of northwesterly trend, along whose crests the earlier Precambrian 

 rocks below the thrusts are exposed. Lying unconformably upon the 

 folded and eroded thrust sheets and chaos is the Funeral fanglomerate, 



probably of late Pliocene age, which consists of fanglomerates and 

 basaltic lava flows. These rocks are deformed by folds and faults so 

 recent that they are still reflected in the topography. The structure of 

 Death Valley is thought to be a broad syncline modified by normal 

 faulting. The Funeral fanglomerate is downfolded into this syncline and 

 broken by step faults, downthrown toward the wide valley, along the 

 east limb. These faults are, therefore, later than the Pliocene ( ?) Funeral 

 fanglomerate. Very fresh scarps in Quaternary alluvium betray recent 

 movement on them. 



There is no evidence in this region of the Nevadan orogeny found to 

 the west and north. There are, however, a number of large thrusts that 

 bring older over younger Paleozoic rocks, which may represent the 

 Laramide orogeny studied by Longwell (1928) and others farther east 

 (Noble, 1941). 



The Amargosa chaos terminates on the south against the east-west 

 Garlock fault. Noble (1926) traced this fault eastward along the north 

 side of the Avawatz Mountains, where it turns southward along their 

 east side with reverse fault relations. Metamorphic rocks of probable 

 Precambrian age are thrust against Tertiary beds (Nolan, 1943). A few 

 miles farther east, Hewett ( 1928 ) has found remnants of a large horizon- 

 tal thrust extending over an area of 30 square miles, along which 

 Precambrian and lower Paleozoic rocks have overridden Miocene (?) 

 sedimentary beds. The eastward movement of the thrust sheet is esti- 

 mated to be at least 10 miles and may be as much as 20 or 25 miles. 



The thrusting of late Tertiary age in southern California in the midst 

 of the Rasin and Range Province is most logically explained, it seems to 

 the writer, as a gravity slide phenomenon incident to vertical uplift. 



LATE CENOZOIC TRENCHES OF THE ROCKY MOUNTAINS 



High Plateaus of Utah 



Extending from the Coconino Plateau south of the Grand Canyon of 

 the Colorado in Arizona northward to central Utah is a system of im-j 

 pressive fault scarps which bound a group of smaller plateaus and inter- 



