PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 263rd meeting was held in the Cosmos Club, January 8, 1913, 

 and the formal communications were presented: 



The hearing of Pre-Cambrian structure on the origin of the Homestake 

 ore body: Sidney Paige. It is suggested that the main Homestake ore 

 body owes its origin to the presence of a strong fault and the subsequent 

 mineralization of a calcareous series. Geologic work has proved the 

 existence of the calcareous series on the surface and in the mine and struc- 

 tural considerations demand the fault. The form of the ore body is 

 that which would be taken if a folded sedimentary series were cut by 

 a fault and replaced by solutions rising along the fault. The particular 

 form which observed facts would require of such a calcareous series as 

 is present agrees with the form of the ore body as determined by mining. 

 Microscopic examination of ores and wall rocks, as far as carried on, 

 support this hypothesis. 



A recent discovery of dinosaurs in the Tertiary: W. T. Lee. Ceratop- 

 sian bones were found during the summer of 1912, nine miles east of 

 Colorado Springs, Colorado, in sec. 3, T. 14 S., R. 65 W., about 500 

 feet above the base of the Dawson arkose (the lower part of the Monu- 

 ment Creek formation of former ^\'Titers). Dinosaurs were found at a 

 locality that had previously yielded a bone of a Tertiary mammal and a 

 number of Eocene plants which, according to Knowlton, belong in the 

 Denver flora. On the evidence of the plant remains the beds containing 

 the dinosaur bones are correlated mth the oldest Tertiary (Raton for- 

 mation) of the Raton Mesa region in southern Colorado and northern 

 New Mexico, and with the Wilcox-Eocene formation of the Gulf region. 



It has long been known that the beds now called Dawson arkose lie 

 with conspicuous unconformity on older rocks that range in age from 

 Laramie to pre-Cambrian, and this unconformity, together with the 

 presence in the beds above it of a Tertiary mammal and of Eocene plants, 

 is thought sufficient to establish the Tertiary age of the Dawson arkose ; 

 and inasmuch as the Ceratopsian bones were found in the same beds it is 

 concluded that some of the dinosaurs existed in early Tertiary time. 



A paleobotanical study of the coal-bearing rocks of the Raton Mesa region 

 of Colorado and New Mexico: F. H. Knowlton. The coal-bearing 

 section in the Raton Mesa region was first (1867-1878) considered by 

 Lesquereux, on paleobotanical evidence, as deferable to the Tertiary and 

 similar in position to the Lignitic, or Eolignitic, of Mississippi, but later 



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