PALEOZOIC CORDILLERAN GEOSYNCLINE 



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that the Uncompahgre Range of the Ancestral Rockies (Chapter 15) 

 extends through in subdued form to a small uplift in northwestern Utah. 

 The sharp margin was not a fault scarp, however, because no coarse 

 flanking debris is known as in Paradox basin. The conspicuous change 

 from shelf to basin is illustrated in Fig. 6.17. The basin was filled, at least 

 on the north by progressive overlap from south to north, with the oldest 

 Pennsylvanian Morrowan sediments on the Manning Canyon shale on 

 the south and with Atokan, Desmoinesian, and Missourian successively 

 deposited on the shale to the north (Rigby, 1958). Limestone and sand- 

 j stone are the principal lithologies in the thick succession, and cyclical 

 ■j sediments dominate the Desmoinesian section in the Stansbury Moun- 

 tains. Quartzite and sandstone dominate over limestone in the Missourian 

 and Virgilian section. 

 A deep and evidently large basin developed in Idaho in which the 

 i Wood River formation accumulated possibly 12,000 feet thick. The forma- 

 ' tion extends westward from the Lost River Range an unknown distance. 

 i The shelf deposits in southwestern Montana are represented by the 

 Quadrant quartzite which attains a maximum thickness of 2600 feet 

 (Scholten, 1957). The Wood River contains fusilinids of Desmoinesian, 

 i Virgilian, and Wolfcampian ages (Rostwick, 1955), and therefore was 

 deposited simultaneously with the upper part of the Oquirrh formation. 



The basal Wood River consists of several hundred feet of conglom- 

 erates, consisting of angular to well-rounded chert and quartzite pebbles. 

 Dark arenaceous limestone beds overlie the conglomerate, and then the 

 rest of the formation, which is the bulk of it, is a monotonous sequence 

 of calcareous sandstones and sandy limestones. Recrystallization and re- 

 placement are common. The sandstones are mostly made up of quartz 

 jgrains with 5 percent or less of feldspar, moscovite, magnetite, and 

 Jzircon. The formation is characterized as miogeosynclinal by Rostwick. 

 Although the sandstones may resemble those of the Quadrant to the 

 'east, it is difficult to see how the conglomerate could have been derived 

 rom an eastern source and transported over the region of sand deposition. 

 jft seems more logical to think of the chert and quartzite pebbles coming 

 rom the west, and thus the inference is drawn that the Antler orogenic 

 'Selt extended from Nevada northward through central Idaho, and 



was the source of the conglomerate and, possibly, of much of the sand. 



The relation of Pennsylvanian rocks to the Antler orogenic belt is 

 diagrammed in Figs. 6.14 and 6.15. 



In Nevada the Pennsylvanian rocks, like the underlying Mississippian 

 are particularly thick east of the orogenic belt, but not quite so coarse. 



Basal beds in the overlap assemblage near the orogenic belt, expecially in 

 Mississippian and Early Pennsylvanian, are usually coarse conglomerates which 

 grade laterally into finer conglomerates and sands, then into silt, clays, and 

 limestone. These clastic beds may be terrestrial locally within the belt, but 

 they are mainly marine adjacent to it. The belt may have been largely sub- 

 merged at times, for widespread marine limestone units interfinger with the 

 elastics. The lenticularity of the overlap sediments as a whole suggests deposi- 

 tion in several separate basins, possibly in a series of straits separated by 

 peninsulas and islands. The presence of coarse elastics throughout much of 

 the Pennsylvanian indicates continued orogenic activity from time to time, 

 perhaps continuing into the Permian (Roberts et al., 1958). 



Volcanoes were active west of the orogenic belt as attested by the 

 presence of volcanic materials particularly in the Pumpernickel and 

 Havallah formations. These deposits are believed by Roberts et al. to 

 have been moved as an allochthonous mass a number of miles from the 

 vicinity of the Nevada-California border eastward to the west side of 

 the orogenic belt, because they have no lithic counterparts nearby. The 

 Calaveras beds in the Sierra Nevada appear to have been metamorphosed 

 more than associated Jurassic beds (refer to Chapter 17), and since no 

 Pennsylvanian rocks have been recognized in the Sierra Nevada or 

 Klamath Mountains, an episode of low-grade dynamic metamorphism 

 has been postulated in Pennsylvanian time. Accordingly on the map of 

 Fig. 6.7 an orogenic belt is shown in the California region. 



A thick quartzite formation overlies a Mississippian schist in southern 

 California and is here placed in the Pennsylvanian although no fossils 

 have been found in it (Larsen, 1948). 



Permian Basins 



The Permian was a time of extensive volcanism in the west, and various 

 kinds of volcanic rocks were spread from the Klamath Mountains on the 

 Pacific coast to central Nevada. The sequence is 5000 feet deep at 

 Rlairsden in the Sierra Nevada and thickens eastward to 12,000 feet in 



