60 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



All of these various bodies are embedded in a carbonate base which in all 

 essential respects is similar to that found in the dolomite of the lower member. 

 The carbonate again forms a compact aggregate of anhedral grains, varying 

 from 0-01 mm. or less to 0-025 mm. in diameter, averaging about 0-015 mm. 



The total analysis of the specimen (No. 1320) afforded Professor Dittrich 

 the following result : — 



Analysis of type specimen, middle Altyn formation. 



Mol. 



SiO, 18-89 -315 



A1 2 3 0-49 -005 



Fe 2 3 0-72 -004 



FeO notdet. 



MgO 16-79 -420 



CaO 23-86 -426 



Na^O 0-47 -007 



K 2 0' 0-57 -006 



H„0 at 110°C 018 



H 2 above 110°C 1-57 -087 



C0 2 36-89 -838 



100-43 

 Sp.gr t 2-802 



A second, partial analysis of the same specimen gave the following data: — 



Insoluble in hydrochloric acid 21-13 



Soluble in hydrochloric acid: 



Fe 2 0, + ALA 0-58 



CaO 2402 



MgO 16-24 



The table of molecular proportions shows that the alumina is too low to 

 match the alkalies of the feldspars actually present. Another determination 

 of alumina and iron oxides of a part of the same specimen gave A1 2 3 , 1-22 per 

 cent; Fe 2 3 , 1-01 per cent; and FeO, 0-33 per cent. 



The ratio of CaO to MgO in the soluble portion is 1-48:1, closely approxi- 

 mating the ratio in true dolomite. Calculation gives the following mineral 

 proportions in the rock : — 



Calcium carbonate 42-6 



Magnesium carbonate 35-3 



Quartz and chert 14-2 



Orthoclase molecule 3-3 



Albite molecule 3-7 



Magnetite -5 



Remainder -4 



100-0 



The rock is plainly an essentially normal dolomite rendered impure by the 

 simple admixture of clastic grains of quartz and feldspar and by the presence 

 of some silica and iron oxide, both of which may be of chemical origin. 



Upper Division. — A specimen typically representing the chief phase of the 

 upper member of the Altyn was collected at the 7,300-foot contour on the back 

 of the ridge south of Oil City. The bed was situated about 100 feet vertically 

 below the top of zone b of the columnar section. 



