MICHIGAN ACADEMY OF SCIENCE. 
109 
ADDITIONAL NOTES ON THE GEOLOGY 
RIVER AREA. 
OF THE DETROIT 
THOMAS NATTRESS. 
In 1 another place I have given the results of investigation in the 
Anderdon Beds on the Canadian side of the Detroit river. Let me now 
present the results obtained in investigating the same limestone beds 
in Wayne county. 
Twenty-five cores were taken out in the Trenton-Sibley area, twenty 
of which penetrated the Anderdon beds. The other five were outside of 
Ihe limestone deposits and south of these, and in each case revealed 
strata of the same character as are presented in the other cores taken 
and below the Anderdon limestone in these cores. 
The Anderdon material is deposited in the same manner as at the 
Amherstburg quarry, in basin formation. Its relation to strata above 
and below is the same as on the Canadian side of the river: immediately 
below the Anderdon is a dolomitic limestone, resting upon dolomite, 
and outcropping outside the outer edge of the Anderdon; immediately 
overlying the Anderdon is the dolomitic limestone hitherto recognized 
as forming the base of the 2 Corniferous (Dundee), the Anderdon out- 
cropping outside the outer edge of this deposit. Cross-section tests 
prove the basin formation throughout the Sibley area. 
Certain features of the Anderdon limestone beds have been noted 
during this investigation that had not hitherto been remarked upon. 
One of these is the occurrence, down in the body of the Anderdon de- 
posit, and at 3 * 5 more than one horizon, of irregular and roughened sur- 
faces like the upper surface of the Anderdon beds in the Amherstburg 
quarry. An interpretation has been put upon the roughened condition 
of this latter surface as pointing toward extensive erosion at the close 
of Anderdon time. 
Another notable feature is this : whereas the Oriskanv Sandstone has 
been identified by competent Authorities at the surface of the weathered 
Anderdon beds in the Amherstburg quarry, and at the surface (or a 
little below it) of the Anderdon beds as exposed in the old well-hole at 
the Sibley quarry; I have found the same silicated condition of the 
Anderdon limestone at two different horizons in the Anderdon beds. In 
the Sibley core numbered IT of the survey of 1011, at 45'G" in the core, 
down to IT'S", there is heavy silication ; and again at 59'6" to 
GO'0" there is the same heav} r silication. The sand grains are unmis- 
takably the same. 
I have in a former paper, referred to already, advanced evidence to 
show that the Anderdon beds should be classed as Devonian. Always 
il3th. Report of the Michigan Academy of Science, 1911, — “The Extent of the Anderdon Beds of 
Essex County, Ontario, and Their Place in the Geologic Column.” 
2 Dundee, (Michigan;) Columbus, (Ohio;) Onondaga, (New York;) and Jeffersonville, (Indiana.) 
3 As in cores No. 19 and No. 12. 
mull. Geol. Soc. Am., Vol. 19, 1907, p. 542, — “New Upper Siluric Fauna from Southern Michigan, — 
Anderdon Exposure.” 
5 Amadeus W. Grabau, William H. Sherzer, and Clinton R. Stauffer (in correspondence.) 
