MICHIGAN ACADEMY OF SCIENCE. 
95 
earth movement. (Ascertained elevations: 578.26,- 584.50, 561.10, 555.00, 
and 538.00.) 
If there has been any earth movement strictly within Anderdon time 
the evidence is to be found in the Modified Anderdon. If that modi- 
fication was due to movement and not to the influence of an adjacent 
land area round about the basin, then it proves in that case a succes- 
sive lowering and raising of the surrounding Silurian dam that con- 
fined the Anderdon waters and excluded — except by intervals — the 
waters of a sea in which older conditions still persisted. 
THE DEPTH OF BOULDER TILL. 
The depth of boulder till on the Detroit river side of the line of 
highest elevations throughout the length of the Anderdon deposit, stands 
definitely related to the interposed rock barrier to the ice sheet in its 
forward movement. From east to west across the basin, 3,300 feet, the 
* depths of till are these: 
10' 2", 14' 0", 21' 6", 32' 6", 50' 0". 
Along the f complete cross section of the valley, east to. west 2,100 
feet: 12' 0", 15' 6", 21' 3", 28' 6", and, in another 1,000 feet westward 
along the Silurian dolomite surface, 40' 0". 
On the other hand the glacial detritus has banked up against this 
same barrier on the east side of it, giving depths in ireverse order: 
28' 6", and 10' 2"; 17' 0" and 9' 0". 
We have thus, doubtless, come upon the explanation of the old De- 
troit river channel already named : First, a shallow Silurian synclinal 
dip; then a rock elevation interposed in the path of the glacier, con- 
sisting of a low Silurian anticlinal bank, with Transitional and Ander- 
don rock superimposed, and all of this elevated by a thrusting move- 
ment. 
CORNIFEROUS AND ANDERDON MATERIAL. 
All the Anderdon limestone material seems to have come in from 
the south, as has been already stated. Because of the greater depth 
of the deposit within the cul de sac basin as compared with the supplying 
valley from the south another valley was suspected leading to the east- 
ward from the basin. That side also was thoroughly tested in the 
hope of finding such a valley. There is a valley— but not of the sup- 
posed age. It carries only Corniferous material. That there is a valley 
of shallow dimensions goes to show a slight letting down of a surround- 
ing anticlinal tongue of Silurian age which has admitted the Cornifer- 
ous sediment from the eastward, none of which came in by way of the 
Malden Valley; around the tip of which upward fold of Silurian, and 
toward the south, the Anderdon has circled about, with normal depth, 
to cross Detroit river in the neighborhood of the upper end of Crosse 
Isle where there is a showing of Corniferous at the surface, to be again 
quarried, in its normal depth, in the bottom of the Sibley quarry, al- 
most opposite the phenomenal depth in the Amherstburg quarry. 
A cross section of the whole Detroit river area between these two 
quarries would show nothing of the Anderdon beds from shore to shore 
*Test holes “I,” “9.” “7,” 19 and 29. 
tTest holes 10, 11, 12, 13, and the Borrowman well. 
JTest holes Nos. 26 and “1”; Nos. 5 and 29. 
