. Bulletin of the Geological Society of America. Geology. OCCURRENCE OF THE FOSSILS 551 the Bighorn mountains. They were also found to occur at frequent in- tervals southward for the next 7 miles to the southern margin of the Big- horn formation, which is on the headwaters of another branch of Powder river, 15 miles northwest of Barnum post-office, in the southeastern por- tion of Bighorn county. The relations at the locality first mentioned above are shown in the following section: B, MADISON LIMESTONE. BIGHORN LIMESTONE s^lJJH BEARING SANDSTONE OWOOD FORMATION Figure 3.—Cross-section of Butt
. Bulletin of the Geological Society of America. Geology. OCCURRENCE OF THE FOSSILS 551 the Bighorn mountains. They were also found to occur at frequent in- tervals southward for the next 7 miles to the southern margin of the Big- horn formation, which is on the headwaters of another branch of Powder river, 15 miles northwest of Barnum post-office, in the southeastern por- tion of Bighorn county. The relations at the locality first mentioned above are shown in the following section: B, MADISON LIMESTONE. BIGHORN LIMESTONE s^lJJH BEARING SANDSTONE OWOOD FORMATION Figure 3.—Cross-section of Butte near Summit of Bighorn Mountains, 23 Miles West of Mayo worth,. Wyoming. The sandstone at this locality is from 6 to 8 feet thick, and it outcrops frequently. It is moderately coarse grained, varies from hard to soft, is massive, and in part shows considerable cross-bedding. Its color varies from dirty buff to light gray, and many of the weathered portions are brownish. Some portions appear oolitic, owing to concretionary growth of the sand grains. The contacts above and below are sharp, but with no marked evidence of unconformity. The underlying beds are Deadwood limestones and shales, the former containing flat pebble conglomerate of intraformational type. A short distance below the contact fossils occur, consisting mainly of Dicellamus politus in large numbers and a few trilobite fragments, apparently Ptychoparia owenii, which are characteris- tic of the Middle Cambrian. The overlying massive limestone is typical Bighorn limestone, containing occasional maclurinas and corals. There can be no question as to the stratigraphic position of the fish-bearing sand- stone below this limestone, for the superposition is plainly exposed here as well as at many localities northward. The Bighorn limestone is here only about 40 feet thick, or one-eighth its thickness in its maximum de- velopment in the northern portion of the Bighorn uplift. As explained above, the diminished thicknes
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