1918] Stock: The Pleistocene Fauna of Hawver Cave 465 



tory of cailon-cutting of these streams involves certain quiescent 

 periods of such length as to allow extensive terraces to be developed, 

 is a matter which can not be adequately discussed as a result of study 

 of the American River directly east of Auburn and of its course in 

 the vicinity of Hawver Cave. Information relating to this problem 

 can perhaps be furnished most satisfactorily by an extensive investi- 

 gation of streams composing the western watershed of the Sierra 

 Nevada. It has therefore not been found possible at Hawver Cave 

 to associate the Pleistocene fauna from the cavern with the formation 

 of terraces along the adjacent river, as has been done for Potter Creek 

 Cave on the McCloud River in Shasta County. 



The present course of the Middle Fork is directly athwart the 

 lens of limestone in which Hawver Cave is situated, and there is no 

 reason for believing that the direction of flow of the stream was 

 materially different during Pleistocene time. Apparently the Amer- 

 ican River must have cut below the old surface, at least to a depth 

 now indicated by the floor of the cave, before extensive leaching of 

 the limestone could have been accomplished. The latter process prob- 

 ably aided the weathering of the limestone, and, due perhaps to a 

 more favorable surface drainage, its results may have been greater in 

 the past. At the present time the limestone is weathered in places 

 on the surface, forming crags and numerous fissures. That such open 

 fissures or chasms were developed in the limestone during the Pleisto- 

 cene, and that large animals either fell or were dragged into them, 

 seems to be indicated by the association of parts of skeletons belonging 

 to individuals of the ground-sloth Nothrothcrium. 



Finally, either the chambers of the cavern were entirely filled 

 with osseous material and debris or, as seems not at all unlikely, their 

 entrances from above were temporarily closed. The present entrance 

 to the cave is approximately on a level with a locally developed flat, 

 the formation of which may have been connected with the sealing of 

 the Pleistocene deposits in the cave. No typical terrace accumulations 

 were observed on the flat and it seems to have been formed as a topo- 

 graphic feature incidental to the erosion accomplished by the Middle 

 Fork and by small tributaries of that branch of the American River. 

 This topographic development may account for the pools of water 

 present in all the principal chambers of Hawver Cave even during 

 the summer months. No noticeable movement was observed in these 

 pools and they probably serve as temporary reservoirs for water which 

 is either slowly seeping to lower levels in the limestone or appearing 



