THE HART MOUNTAIN OVERTHRUST AND 
ASSOCIATED STRUCTURES IN PARK 
COUNTY, WYOMING: 
¢. L. DAKE 
Tulsa, Oklahoma 
INTRODUCTION 
Field work during the summer of 1916 brought to light what 
is believed to be one of the most interesting major thrusts yet 
described in the northern Rocky Mountains. So far as the writer 
is aware, the true nature of this fault has not heretofore been 
described, although Fisher? refers to it in discussing the structure 
of Hart Mountain. The area studied embraces a narrow strip 
of territory lying between the area covered by Fisher’s Big Horn 
Basin report, just mentioned, and the Absaroka quadrangle on the 
west. 
STRATIGRAPHY 
The stratigraphy of the region is essentially the same as that 
given by Fisher in his above-mentioned paper describing the 
area adjacent on the east. The divisions of the Cretaceous adopted 
in mapping are those used by Lupton, since they represent more 
detailed work than was done by Fisher. Hewett‘ has also 
described the stratigraphic column in some detail in the region 
immediately east of the area mapped:-by the writer. The follow- 
ing table of formations is largely compiled from the three reports 
mentioned above. Detailed description of the various strati- 
graphic units will not be given, except in the case of the so-called 
Fort Union(?) regarding the age of which there may be some 
question. 
t Published by permission of the Wyoming State Geologist. 
2 C. A. Fisher, U.S. Geol. Survey, Prof. Paper No. 53, p. 37. 
3 Lupton, ‘‘Oil and Gas near Basin, Wyoming,” U.S. Geol. Survey, Bulletin 621L. 
4 Hewett, ‘‘The Shoshone River Section,” U.S. Geol. Survey, Bulletin 541, pp. 89- 
113. 
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