1 2 TJie Anterica?i Geologist. July, iss)9 
Moraines of Recessioii in the Lake Basins. 
The precise location of the ice-dam at different stages of its 
recession is made possible only by the existence of the mor- 
•lines of recession. They show the successive positions at which 
the ice-front halted and thus furnish information far more defi- 
nite and accurate than any that could be gathered from a mo- 
notonous drift sheet without terminal moraines. It was there- 
fore necessary to trace the moraines that cross or descend into 
the lake basins before the precise place of the ice-dam at any 
stage could be known. Mr. G. K. Gilbert took the first step 
in this direction in 1870, when he made a geological survey of 
the Maumee valley. He found a terminal moraine of the gla- 
cier passing just east of Defiance, O., and curving thence south 
and southeast past Findlay and north and northeast past Ad- 
rian, Mich. Defiance is at its apex and this moraine is now 
known as the Defiance moraine.* This moraine spans the 
Maumee valley from side to side completely and marks, as we 
now know, the first position of the ice-dam in the Erie basin. 
Although Mr. Gilbert did not at that time recognize it as 
marking the place of an ice-dam, its significance in this re- 
spect was made plain on the publication of Dr. J. S. New- 
berry's hypothesis of ice-dams.t 
For many years this moraine stood as the only one that had 
been traced continuously across a lake basin and hence marked 
the place of the only ice-dam that had been accurately located. 
The lake held in front of this dam will be described later on. 
The Erie-0?itario Series. With the early acceptance of 
Dr. Newberry's hypothesis a new field of investigation was 
*Its course is well shown on Mr. Gilbert's map of the Maumee 
valley in the "Geology of Ohio," vol. I, 1873, opposite page 541. In 
vol. II of the same survey, 1874, P- 432, N. H. Winchell calls this 
moraine the "Blanchard ridge," and he also calls the moraine which 
passes through Fort Wayne, Ind., the "St. Mary's ridge." These names 
were taken from rivers that flow along the front of the moraines in the 
southern half of the valley, but in the northern half there are other 
rivers in the same relation to the s&me ridges. The completion of the 
moraine series northward to lake Huron disclosed the fact that there 
is a well known city at or near the apex of each moraine. These 
names are better known and are more easily understood as applying 
to the whole extent of each ridge on both sides of the valley. Thus 
we have the Fort Wayne, Defiance, Toledo, Detroit and Port Huron 
moraines. 
t"Geology of Ohio." vol. II, 1874, pp. 8 and 51-52. 
