PALEOZOIC CORDILLERAN GEOSYNCLINE 



75 



The Coffee Creek and Spotted Ridge formations are reported as in- 

 tensely folded, but no mention is made of metamorphism (Merriam and 

 Berthiaume, 1943). They lie in a tectonic belt of deformed strata in which 

 ' the rocks on the west ( Klamaths ) and on the east ( Baker area ) are meta- 

 morphosed, and it is puzzling that these also are not metamorphosed. 



The Spotted Ridge is overlain by the Coyote Butte formation. A slight 

 i angular unconformity separates the two. The Coyote Butte is made up 

 almost entirely of massive limestones. Some chert pebble conglomerates 

 i are present near the base. The age is probably Lower Permian. 



A prominent angular unconformity exists between the Paleozoic beds 

 i of central Oregon and the overlying Triassic conglomerates which attain 

 1 a thickness of 4000 feet. 



In the Baker quadrangle of eastern Oregon, Gilluly (1937b) described 

 a formation, the Burnt River schist, which, chiefly because of greater 

 metamorphism than that of known Carboniferous rocks nearby, he cau- 

 tiously treats as older. The rock varieties are greenstone schists, quartz 

 ] schist, conglomerate schist, limestone, slate, and quartzite, and make up a 

 series at least 5000 feet thick, maybe several times as much. The various 

 1 types mentioned grade into each other. 



Gilluly visualizes the origin of the strata as follows: 



. . . pyroclastic material was added in amounts varying from time to time 

 ^to a basin of sedimentation to which at some times sand and at others clay, 

 widi some carbonates, were being supplied. When volcanic contributions were 

 small, the deposits were such as have yielded the quartzites and carbonaceous 

 Ulates now found, but when the volcanic material increased relative to the 

 } normal terrigenous sediment the deposits were such as have yielded the inter- 

 mediate rocks. At times such floods of volcanic material were contributed that 

 practically unmixed tuff was formed. 



The Burnt River schist has lithologic similarities with the Calaveras for- 

 mation, but differs, it seems, in generally having greater metamorphism 

 md an absence of chert. The Burnt River appears from published de- 

 scriptions to be surprisingly similar to the Salmon schist of the Klamaths, 

 which is probably pre-Silurian. See Figs. 6.17 and 6.18. 

 j Above the Burnt River schist is the Elkhorn Ridge argillite about 5000 

 eet thick. It is probably the most widespread of the pre-Tertiary forma- 

 ions and is a thick series of argillite, tuff, and chert with subordinate 



C / / » 6 — / I ^ -" PHOSPHATE ■ 



PERMIAN 



Fig. 6.8. Thickness and paleogeographic map of the Permian. S.G. and L.A. ARCH means Sierra 

 Grande and Las Animas arch, which rose at end of Permian. 



