STRATIGRAPHY 



SOUTHERN WYOMING 



The Medicine Bow formation is an alternating succession of shales, sandstones, 

 and coal beds resting conformably on the Lewis shale in the Hanna and Carbon 

 basins of south central Wyoming. The first comprehensive report on this region 

 was by Veatch,^ wlio designated the formation as "Lower Laramie" on the basis 

 of stratigraphic position and "the absence of marine fossils." For essentially the 

 same beds Bowen ^ subsequently proposed the name Medicine Bow formation, 

 which has since become generally accepted. Regarding the fossils found in the 

 formation, Bowen wrote as foUows: 



"The formation contains remains of fresh and brackish water invertebrates, land plants, 

 and bones of vertebrates. The plants are regarded by F. H. Knowlton as of the same age as the 

 plants of the Laramie of the Denver Basin. The invertebrates are considered by T. W. Stanton 

 to belong to the fauna of the Lance formation. The bones belong in part to the ceratopsians, but 

 no specimens have been found that are sufficiently diagnostic for even generic determination." 



In a later report on the same general region, Dobbin, Bowen, and Hoots ^ 

 described the formation in more detail and included within its lower limits the 

 " sandstonc beds with a marine fauna of Fox Hills type." It is clearly evident from 

 both Veatch's and Bowen's statements as quoted above that this marine sandstone 

 had previously been excluded from the Medicine Bow formation and regarded as 

 the upper portion of the Lewis shale. The various interpretations of the late 

 Cretaceous and early Tertiary deposits of the region are shown in figure 2, which is 

 compiled from the three reports cited. 



The writer's interpretation of the section is presented in the right-hand colimm 

 of figure 2. The recognition of the Fox Hills formation between the Lewis and 

 the Medicine Bow is based upon the occurrence of the Sphenodiscus zone, which is 

 of restricted Fox Hills age,^ at numerous locaUties in the region, and upon the marked 

 changes in the aggregate lithology of the sequence. Veatch apparently collected no 

 fossils from these beds, nor did he mention any changes in Uthology in the upper 

 portion of the LeM'is formation or the lower portion of the "Lower Laramie." 

 Bowen^ reported the presence of a persistent gray sandstone near the top of the 

 Lewis shale, but did not mention the massive, coarse, concretionary sandstones near 

 the base of the Medicine Bow formation. He apparently collected no fossils from 

 these units at that time. The subsequent report by Dobbin, Bowen, and Hoots 

 recordcd characteristic Fox Hills species including Sphenodiscus lenticularis (Owen) 

 Meek near the top of their Lewis formation, and "a few marine beds with in- 

 vertebrate fossils of Fox Hills types intercalated in the basal part" of the Medicine 

 Bow formation.'^ Although they did not recognize the Fox Hills formation as a 



' Veatch, A. C, Coal Fields of Easl-cenlral Carbon County, Wyonnng, U. S. Gcol. Survey Bull. 316, 244-200, 1907. 

 ^Bowen, C. F., Stratigraphy of thc Hanna Basin, Wyoming. U. S. Geol. Survey Prof. Paper lOS-L. 227-235, 1918. 

 ' Dobbin, C. E., Bowen, C. F., and Hoots, H. W., Geology and Coal and Oil Kesources of thc Hanna and Carbon Basins, 

 Carbon County, Wyoming, U. S. Gcol. Survey Bull. 804. 9. 23, 1929. 

 * Reeside, J. B., Jr.. written communication, May 9, 1935. 

 ' Bowen, C. F., op. cit., 228, 229. 

 « Dobbin, C. E., Bowen, C. F., and Hoota, H. W., op. cit., 21, 22. 



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