432 C. A. White — Relation of the Laramie Group 



Aet. XXXVII. — On the relation of the Laramie Group to 

 earlier and later Formations ; by Chaeles A. White. 



[Published by permission of the Director of the U. S. Geological Survey.] 



While some geologists and paleontologists have claimed the 

 Laramie Group as belonging to the Tertiary, others have as 

 earnestly asserted its Cretaceous age. In the course of my 

 own investigations I have found so many of the paleontological 

 characteristics of that formation to be of little or no value as 

 indicating its age, and other evidence to be so conflicting in 

 character,* that, in my somewhat numerous writings concern- 

 ing that group, I have hitherto treated it as representing a 

 gradual transition from the Cretaceous to the Tertiary. In- 

 vestigations concerning the physical conditions which attended 

 the deposition of that great group of strata, and the biological 

 conditions which prevailed during its accumulation are cer- 

 tainly of far more importance than the mere question of its 

 contemporaneity with other formations, which, as regards any 

 formation, can at best be learned only approximately. Still 

 this latter question is by no means a trifling one, and any facts 

 bearing upon it ought to receive due consideration. The ob- 

 ject of this article is to record certain lately acquired facts re- 

 lating to this question, and to present the bearing upon it of 

 others which have before been published. 



During the twelve years preceding the autumn of 1887, in 

 which I had made extensive studies and observations concern- 

 ing the Laramie Group, I was never able to obtain any per- 

 sonal knowledge of- the actual stratigrajDhical relation of that 

 group to any of the marine Tertiary groups which border 

 various portions of ]N"orth America. I had studied the Lara- 

 mie in numerous . districts from the State of ISTuevo Leon, 

 Mexico, on the south to northern Montana on the north ; and 

 wherever the base of the formation was observable it was 

 found to rest directly and conformably upon the uppermost of 

 the marine Cretaceous formation s.f Furthermore, wherever 

 any strata were found resting upon the Laramie they were 

 always those of the great fresh- water Tertiary series ; but I 

 had not then traced the Laramie into a district within which 

 marine Tertiary strata were known to exist. That is, in tra- 



* See White. C. A., On the commingling of ancient faunal and modern floral 

 types in the Laramie Group. This Journal, III, vol. xxvi, pp. 120-123. 



f For an account of the intimate stratigraphical relation of the Laramie to the 

 marine Cretaceous formation next beneath it ; and of a partial faunal connection 

 of the Laramie with freshwater Tertiary formation next above it, see this Journal, 

 III, vol. xxxiii, pp. 864-374. 



