ABSTRACl^S OF PAPERS 233 



OCCURRENCE OF NOTHROTHERIUM IN PLEISTOCENE CAVE DEPOSITS OF 



CALIFORNIA 



BY CHESTER STOCK 



(Abstract) 



The ground-sloth Nothrotherium was originally described from material 

 found in cave deposits of Brazil. A recent study of the ground-sloths from 

 the Pleistocene deposit of Samwel Cave, Shasta County, California, has shown 

 the presence of Nothrotherium associated with Megalonyx. NotJirotherium is 

 known also from Potter Creek Cave, in Shasta County, and from Hawver Cave, 

 in Eldorado County. The range of this ground-sloth in North America is ap- 

 parently more restricted than that of Mylodon or Megalonyx. Except for its 

 occurj-ence in California, the genus is known only from the Pleistocene of 

 Texas, where it has recently been recognized by O. P. Hay. 



CRETACEOUS AND TERTIARY HORIZONS IN THE MARYSVILLE BUTTES 

 BY ROY E. DIOKERSON 



(Abstract) 



Recent investigations at Marysville Buttes, an ancient volcano of the Sacra- 

 mento Valley, have revealed the presence of the Knoxville and Chico groups. 

 The areas mapped as lone in the Marysville folio are composed, in part at 

 least, of four different terrains — the Knoxville, the Chico, the Tejon (Sipho- 

 nalia sutterensis zone), and the Sutter formation. The last is a land-laid de- 

 posit consisting largely of rhyolitic debris of the first volcanic eruption. These 

 terrains were in turn disturbed by an andesitic intrusion, thrown on edge and 

 faulted in places. 



The sequence of events which gave us the Marysville Buttes in their present 

 form appears to be as follows : 



(1) The accumulation of limestones and shales of Knoxville age in a great 

 geosyncline, the eastern border of which was probably in the vicinity of the 

 present site of the Marysville Buttes. 



(2) A recession of the sea from the eastern border of the geosyncline during 

 the deposition of the Horsetown horizon. 



(3) The lowering of the continental margin and the deposition of Chico- 

 Cretaceous strata by a transgressing sea from the west. 



(4) A great time interval during which this site was land. 



(5) Submergence at the end of Tejon time, which resulted in the deposition 

 on the outer edge of the continental shelf of Eocene strata composed of fo- 

 raminiferal shales, the deep-water equivalents of the inshore lone of the Sier- 

 ran foothills. 



(6) Uplift. 



(7) An intrusion of rhyolite and consequent upturning and faulting of Cre- 

 taceous and Eocene strata and outpouring of rhyolitic flows and ash deposits 

 (the Sutter formation) on these faulted and folded sedimentaries. 



(8) A period of erosion during whicli a large portion of the Sutter forma- 

 tion was removed. 



(9) An Intrusion into these older formations mentioned above and outpour- 

 ing of andesitic materials from a great central volcano. 



