proceedings: geological society 51 



quin and 7 miles still further south, Cambrian quartzite in every case 

 overriding Mississippian limestone; (3) local doming and eastward 

 reverse faulting around the intrusive Cottonwood granite stock; (3) 

 fissuring and mineralization following the Cottonwood intrusion; (4) 

 late normal (block) faulting which developed the Basin range. The 

 latter is especially well exposed in the low western flanking ridges between 

 Mt. Nebo and Santaquin, where the faults which lie along depressions 

 can be proved by the discordant relations of the bed rock. The block 

 faulting took place after the post-Eocene volcanic eruptions. 



New data on the ^^Knox dolomite" in Tennessee and the "Ozarkian" 

 in Missouri: E. O. Ulrich. Robert Anderson, Secretary. 



At the 261st meeting, held at the Cosmos Club on November 27, 

 1912, under informal communications, the follomng paper was pre- 

 sented : 



An occurrence of yetroleum near Cody, Wyoming: D, F. Hewett. A 

 petroleum spring was observed under unique conditions in the Akaroka 

 Mountains, in northwestern Wyoming, during the summer of 1912. It 

 is located on the west bank of Sweetwater Creek, 2| miles north of its 

 junction with the North Fork of Shoshone River, and is therefore about 

 26 miles due west of the town of Cody. The geology of the region is 

 described by Hague in Folio No. 52, and the spring is situated in the 

 basic andesite flows of Miocene age on the line (Lat. 40° 30') between 

 the Ishawooa and Crandall sheets. 



The spring is unique in that it lies within 100 yards of several small 

 sulfur deposits, situated on the east side of Sweetwater Creek. The 

 sulfur deposits are identical in nature to those 12 miles north on Sun- 

 light Creek, which were examined in 1911, and a report upon which 

 appears in U. S. Geological Survey Bulletin No. 530, part 0, 1911. 

 The deposits embrace two classes of material: (1) sulfur which lies along 

 the walls of open fractures in the lavas, ancl from which gases con- 

 taining CO2, CH4 and HoS are issuing, and (2) sulfur filling the inter- 

 stices of gravels and s\irface debris along stream channels. The second 

 class of material probably covers fracture zones. The oil spring is 

 opposite an area 100 feet square into which prospect pits have been 

 sunk showing sulfur cementing angular rock debris to a depth of 9 feet. 

 Other smaller deposits of sulfur lie 700 feet farther up the creek. 



Oil was first recognized issuing from the sands adjoining the creek. 



In the hole which was dug along the bank, water and oil slowly 

 accumulated and several quarts of clear light oil were thus collected 

 during the summer of 1911. During the writer's visit a pit was dug 

 near the location of the old one which had been destroyed by freshets. 

 The sand at this point is dark brown and has an asphaltic odor, but 

 otherwise is such as would form bars along rapid mountain streams. 

 In the short time at the writer's disposal only enough oil was collected 

 to give assurance of its identification, but not enough for analysis. 



Tho the superficial rocks of this region are igneous flows and breccias, 

 these rocks overlie a great thickness of sedimentary rocks ranging in 



