TWELVE TERMIjSTAL MORAINES. 189 



were formed by the trampling and pawing of butialoes in rnbbing on the 

 bowlders, which were thereby sometimes worii and polished as perfectly as 

 could be done by art. ' 



TERMINAL JXORAINES. 



Exploration of the terminal moraines in the northeast edge of South 

 Dakota, accumulated on the west margin of the Minnesota lobe of the ice- 

 sheet, northward to the Head of the Coteau des Prairies, was included in 

 the work of the writer during 1880 for the Minnesota Geological Survey. 

 The three outer moraines are typically developed and distinctly separated 

 in that portion of their course, as well as through the adjoining southwest 

 part of Minnesota ; and from their description for this district ^ they have 

 been denominated by Professor Chamberlin the Altamont, Clary, and Ante- 

 lope moraines. Besides these, nine others, to a total of twelve in all (as 

 shown on Pis. Ill and XVII), lying along a large part of their extent in 

 successive order from south to north, and apparently marking consecutive 

 stages in a wavering recession of the ice-sheet, are recognized in Minnesota 

 and receive names in the annual and final reports of the State survey from 

 localities where they are notal)ly prominent or distinct. In western Min- 

 nesota the}" seem to constitute a simple series, each in order advancing from 

 south to north and northeast being of somewhat later formation than the 

 one preceding ; liut in the central and eastern portions of the State, from 

 the Leaf Hills southeast to Minneapolis and St. Paul, and in their course 

 eastward into northern Wisconsin, consecutive moraines are merged together, 

 and even the later are found overlapping the earlier in the series. 



'Notes of the Tvkle ai-ea over which such bowlders polished by buffaloes are found, and of 

 other traces of these animals still visible on the prairies and plains, from which they have so recently 

 vanished, are given in Geology of Minnesota, Vol. II, p. 516. 



Occasionally a bowlder worn by the rubbing of buiialoes has been pushed back and forth by 

 them while the surrounding hollow was being formed by their pawing and by the winds blowing 

 away the dust from it, until the rock has been thus undermined and lowered evidently at least 3 or 4 

 feet below its original position, so that its top now lies beneath the general level of the land. Among 

 several examples of this result seen by me, one may be noted which was found about 60 feet northwest 

 of the quarter-section stake between sections 26 and 35, Mekinock, Grand Forks County, N. Dak. 

 This bowlder, weighing several tons, measures about 7 feet in length and 5 feet in width, and stands 

 up li to 2 feet out of the ground; yet it is so situated in a bowl shajjcd hollow, 30 to 40 feet in 

 diameter and 3 feet or more in depth, that the top of the rock is 1* feet below the uniform level sur- 

 face on all aides around the hollow. It is a light-gray, rather coarse-grained hornblendic granite, 

 very compact and not afl'ecteil by weathering; and its corners and edges are finely poli.whed. 



-Geol. and Nat. Hist. Survey of Minnesota, Ninth Annual Report, for 1880 ; Final Report, Vols. 

 I and II. 



