abstracts: geology " 249 



GEOLOGY. — Geologic structure of the northwestern 'part of the Paivhuska 

 quadrangle, Oklahoma. K. C. He.\ld. U. S. Geoloj^ical Survey 

 Bulletin G91-C. Pp. 44, with maps and sections. . 1918. 

 This paper describes those geologic features of a portion of the 

 Pawhuska quadrangle, Oklahoma, which bear on the occurrence, dis- 

 covery, and development of commercial quantities of oil or gas. The 

 rocks that crops out in the area are shown in a generalized stratigraphic 

 section, but the characteristics and extent of certain beds of value in 

 mapping the structure of the region are described full}^ The probable 

 character of the rocks to a depth of 4000 feet below the surface is also 

 described, and some evidence is given by graphic representation of 

 well records and stratigraphic sections. ' R. W. Stone. 



GEOLOGY. — The Flaxville gravel and its relation to other terrace 

 gravels of the northern Great Plains. Arthur J. Collier and W. 

 T. Thom, Jr. V. S. Geological Survey Professional Paper 108-J. 

 Pp. 5. 1918. 

 The Flaxville gravel in Montana is from a few feet to 100 feet thick 

 and is composed of well-rounded quartzite and argillite pebbles from 

 the Rocky Mountains but it contains also sand, clay, marl, and volcanic 

 ash. It rests upon a series of plateaus which are cut on the Fort Union, 

 Lance, and Bearpaw formations and which range in altitude from 2600 

 feet at the east to 3200 feet at the west. Fragmentary fossils col- 

 lected at 25 well-distributed localities show that the formation can 

 not be older than Miocene nor younger than early Pliocene. 



R. W. Stone. 



GEOLOGY. — The Dunkleberg mining district, Granite County, Montana. 



J. T. Pardee. U. S. Geological Survey Bulletin 660-G. Pp. 7, 



with 1 plate and 1 figure. 1917, 

 The ore deposits, which have been worked intermittently during 

 the last 30 years and have produced $200,000 worth of silver and lead, 

 occur in limestone, sandstone, and shale of Cretaceous age and also in 

 diorite sills that have invaded these rocks. Except one, which is a 

 contact-metamorphic body of zinc ore, the deposits are simple quartz 

 veins in fissures that follow inclined bedding planes or cut across the 

 sedimentary beds and the sills. Silver-bearing galena and carbonate 

 derived from it are the most valuable minerals, though zinc blende 

 is locally abundant. J. T. P. 



