180 knowlton: age of morrison formation 



GEOLOGY. — Note on a recent discovery of fossil plants in the 

 Morrison formation. x F. H. Knowlton, Geological Survey. 



There has been a good deal of discussion within the past few 

 years regarding the stratigraphic position of the Morrison for- 

 mation, that is, as to whether it should be placed in the upper 

 part of the Jurassic or the lower portion of the Cretaceous. 

 The divergence of opinion on this point among stratigraphers 

 and paleontologists was well brought out in the symposium on 

 the " Close of Jurassic and opening of Cretaceous time in North 

 America," given before the Paleontological Society at the 

 Philadelphia meeting in 1914, 2 though the concensus of opinion 

 appeared to favor placing it in the Cretaceous. 



Heretofore, with the exception of some 20 nominal species of 

 cycad trunks found in the Freezeout Hills in Carbon County, 

 Wyoming, no fossil plants have been reported from the Morrison. 

 This deficiency is now in a small measure supplied by the fortun- 

 ate discovery of a plant-bearing horizon in the Morrison near 

 Little Cottonwood Creek, in the eastern part of Bighorn Basin, 

 Wyoming. Mr. C. T. Lupton, of the United States Geological 

 Survey, found this locality in 1915 and sent in a small collection. 

 Mr. Lupton has kindly supplied ,me with the following data 

 regarding the location and stratigraphic relations: 



The fossil leaves I sent in were collected by my assistant, Mr. E. M. 

 Parks, in the NW. | sec. 14, T.47 N., R. 89 W., on the east side of Little 

 Cottonwood Creek, an intermittent tributary of No Wood River. 

 This place is about 5 miles west slightly north of the town of Ten Sleep, 

 and about 1^ miles north of the Worland-Ten Sleep road where it 

 crosses the former stream. 



The leaves occur in a thin bed of light shaly sandstone which lies 

 just beneath a prominent 50-foot bed of white ledge-making sandstone 

 containing a little conglomerate at its base. This prominent sandstone 

 is variable in thickness and constitutes the basal part of the Cloverly 

 formation as identified by Darton. The varicolored beds below this 

 conglomeratic sandstone are characterized in many places by gastro- 

 liths ('stomach-stones'). 



1 Published with the permission of the Director of the U. S. Geological Survey. 



2 Papers by Osborn, Lee, Mook, Lull, Berry, and Stanton. Bull. Geol. Soc. 

 America 26: 295-348. 1915. 



