346 T. W. STANTON CRETACEOUS-TERTIARY BOUNDARY 



Frontier formatiou. At Coalville there is also the evidence of a very 

 coarse conglomerate 60 feet thick at or near the top of the Colorado 

 group. There are lenses of coarse conglomerate near the middle of the 

 Colorado at Cody, in Bighorn basin, Wyoming, and a still greater devel- 

 opment of conglomerate at about the same horizon at Livingston, Mon- 

 tana. These conglomerates are unquestionably near-^hore .deposits, 

 which indicate land of considerable elevation. ;_:.^ , ::_:l: r- __. :j'i,. 



During the Montana epoch there is abundant j.evid_enee. Qf crscillatin;g 

 movements and resulting more or less teinporai;;}' land con.ditMns froiO 

 northern Wyoming northward through . Mont^nti , ^d in tjie: Canadian 

 territories. This is seen in'tliet-mil beds -and land plants of the-^Ea^le 

 sandstone and the coals and land and fresh-\vater faunas of. the Judith 

 River formation, in each case found in formations interstratified with 

 ])urely marine deposits. In the Blackfoot Indian reservation and farther 

 north beyond the international boundary the ratio of continental to ma- 

 rine deposits was greatly increase-l, and during the epoch there, was only 

 one decided incursion of the sea, represented by the Bearpaw shale, which 

 passes by gradual transition through overlying littoral and brackish- 

 water deposits into continental deposits. In the Bighorn basin the. final 

 change from marine to continental deposition came earlier, near the 

 beginning of the Montana. 



In the country surrounding the Crazy Mountains and near Livingston, 

 Montana, there is evidence of another kind that the late Cretaceous was 

 not a time of quiet, uniform, marine, submergence. On the contrary, 

 there was great volcanic activity, beginning early in the Montana epoch, 

 while the. Eagle sandstone was being deposited and continuing, probably 

 with many interruptions, until well into the Eocene, or at least furnish- 

 ing material for sediments until that date. The debris from these erup- 

 tions was deposited in part above sealevel and in part beneath it, in some 

 places fingering out between more nearly normal marine sediments. 

 These andesitic tuffaceous deposits constitute the Livingston formation, 

 w^hich was described by Weed 20 years ago as resting unconformably on 

 the "Laramie," and which has frequently been cited as similar to the 

 Denver formation in charax^ter, relations, and age. The more detailed 

 stratigraphic and areal work of Stone^ and Calvert has shown that the 

 unconformity described by Weed as at the base of the Livingston has no 

 existence in fact, and that while the upper part of the formation may be 

 as late or even later than the Denver a large part of it was formed during 



8 R. W. Stone and W. R. Calvert : Stratigraphic relations of the Livingston formAtion 

 of Montana. Economic Geology, vol. 5, 1910, pp. 551-557, 652-669, 741-764. 



