88 CONTRIBUTIONS TO PAL^ONTOLOGY 



saur species known from the area in his monograph on the revision of the Ceratopsia.* 

 My own preliminary statements regarding the plants from the Lance and a discus- 

 sion of their stratigraphic relationships have preceded the present comprehensive 

 report.^ 



The palaeobotanical conclusion that the Tullock and Ludlow beds, generally 

 regarded as the upper member of the Lance formation in regions to the north of the 

 Lance Creek area, are of early Paleocene age has recently been substantiated by the 

 study of the foraminifera of the marine Cannonball beds, which interfinger westward 

 into the Ludlow.^ 



STRATIGRAPHY 



General Section 



The sedimentary rocks exposed in the Lance Creek area, as shown in figure 2, 

 are of Upper Cretaceous, Paleocene, and Ohgocene age. The generaUzed section of 

 formations is as foUows: 



Tertiary 



Oligoeene : 



White River group (nonmarine) 

 Unconformity 

 Paleocene: 



Fort Union group (nonmarine) 

 Upper Cretaceous 



Lance formation (nonmarine) 



Fox Hills sandstone (marine) 



Pierre shale (marine) 



From the Pierre shale up into the Fort Union group the succession is one of ap- 

 parently continuous deposition. AU these formations crop out as a result of erosion 

 on the steep to gently dipping northwestern Umb of an asymmetrical anticUne. The 

 sediments of the White River group Ue essentiaUy horizontaUy on the dipping, 

 eroded Pierre shale in the southern part of the region. The best exposures of the 

 formations are to be seen in the banks of the main streams and their numerous 

 tributaries, aU of which are practicaUy dry during the summer months. In the 

 descriptions which foUow, details concerning the Pierre shale and the White River 

 group are omitted, as these beds have no immediate bearing on the problems con- 

 cerning the Lance formation. 



Fox Hills Sandstone 



From the typical dark-gray clay shales of the Pierre shale, exposures in the 

 Lance Creek area show a gradual transition upward into a succession of Ught-gray 

 and grayish-brown sandstones. These have been referred to the Fox HUls sand- 

 stone ■• on the basis of their stratigraphic position, their gross Uthology, and their 



' Lull. R. S., Mem. Peabody Mus. Nat. Hist., vol. .3, pt. 3, 19,33. 



» Dorf, E., Carnegie Inat. Wash. Pub. No. 608, pt. I, 33-36, 1938; BuU. Geol. Soc. Amer., vol. 61, 213-236, 1940. 



» Fox. S. K., Jr., and Rosa. R. J., Jr.. Bull. Ocol. Soo. Amer., vol. 51, no. 12, pt. 2, 1970, 1940. 



«Stanton. T. W., and Knowlton, F. H.. BuU. Gcol. Soc. Amer., vol. 8, 128-132, 1897. Dobbin, C. F,., and Recside, 

 J. B., Jr., U. S. Geol. Surv. Prof. Paper 158-B, 18-20, 1929. Waagfe, K. M., The StralUjraphy and Palseoniology of the Fox 

 HilU Formation in the Lance Creek Area, Niobrara Counly, Wuoming, scnior thesia, Priuceton University, 4, 43-62, 1939. 



