454 ARTHUR BEVAN 



marine Cretaceous fauna/ and the close relationship of the Lance 

 and Fort Union formations. If the Lance is of Cretaceous age, the 

 inclusion of the Fort Union in the Mesozoic is strongly supported 

 by the lithologic similarity of the two formations, the homogeneity 

 of the floras,^ and the apparent lack of any pronounced hiatus in the 

 Lance-Fort Union sequence. Moreover, upon the basis of recent 

 studies of vertebrate remains in these and similar formations, the 

 conclusion has been reached that the Fort Union belongs in the 

 Cretaceous system.^ 



The Red Lodge district thus far has afforded no evidence bearing 

 upon these phases of the problem. It is, however, a pertinent fact 

 of considerable significance that the Fort Union of this region was 

 involved in the first orogeny that deformed the underlying Mesozoic 

 formations. 



South of the Montana line within two miles of the mountain 

 front is a line of hills formed of steeply tilted strata of a rather 

 loosely cemented conglomerate which is composed mainly of well- 

 rounded pebbles and cobbles of Paleozoic Hmestones. The age and 

 relations of these beds have not been carefully determined, but from 

 their position they seem to be either a part of the Fort Union or the 

 marginal outcrops of the Wasatch of the Bighorn Basin. Although 

 their Hthology is more in accord with the pubKshed descriptions of 

 the latter, their position and structure suggest that they may be a 

 member of the Fort Union. They may possibly even be of inter- 

 mediate age. 



Another conglomerate, the Linley conglomerate, is present a 

 short distance beyond the range, lo miles northwest of Red Lodge, 

 where it "lies with marked unconformity on tilted and eroded Fort 

 Union beds."'' It consists of about 300 feet (maximum) of sand 

 and pebbles of igneous rocks from the crystalline core of the range, 



' E. R. Lloyd and C. J. Hares, "The Cannonball Marine Member of the Lance 

 Formation of North and South Dakota and Its Bearing on the Lance-Laramie Prob- 

 lem, Jour. Geol., XXIII (1915), 253-57. 



^F. H. Knowlton, "Are the Lance and Fort Union Formations of Mesozoic 

 Time?" Science, LIII (1921), p. 307. 



3 W. D. Matthew, op. cit. 



'' W. R. Calvert, " Geology of the Upper Stillwater Basin, Stillwater and Carbon 

 Counties, Montana," U.S. Geol. Survey Bull. 641-G, 1916, p. 203. 



