MICHIGAN ACADEMY OF SCIENCE. 
87 
THE EXTENT OP THE ANDERDON BEDS OF ESSEX COUNTY, 
ONTARIO, AND THEIR PLACE IN THE 
GEOLOGIC COLUMN. 
REV’D THOMAS NATTRESS. 
Considerable interest lias centered in the Anderdon Limestone Beds 
of Anderdon Township, Essex County, Ontario, since Garbau pronounced 
them hitherto unrecognized in 1907 and gave to the beds the name they 
now bear. That interest was intensified by Professors Sherzer and 
Grabau when they claimed to have identified this limestone with cer- 
tain problematical beds deep down in the Silurian strata in the Salt 
Shaft at South Detroit. 
A year ago in presenting before the Academy a paper on The Contour 
of the Svlvania Sandrock and Related Strata in the Detroit River Area, 
I took occasion to adduce some suggestive evidence that the supposed 
intercalated beds at the salt shaft and the Anderdon beds have each 
their own independent horizon. 
Since then it has fallen to my lot to superintend the taking out of 
thirty drill cores to determine the extent of these limestone beds in 
Anderdon and Malden townships. Ten other cores had already been 
taken out in and near the Amlierstburg Quarries in Anderdon. In ad- 
dition to these forty drill cores, there are three quarry holes through 
the high grade limestone, to facilitate the estimate. The accumulated 
evidence has too broad a bearing not to be presented in the endeavor 
that has been yours and mine to solve the problems of the Detroit river 
area. 
Professor Grabau has himself differentiated the Anderdon limestone in 
his Stratigraphic and Palaeontologic Summary of the Monroe Forma- 
tion. Under the head of *“Upper Monroe Faunas” he groups as a unit 
the faunas of the Flat Rock, Anderdon and Amlierstburg (Detroit 
river bottom) beds. Of the faunas of this supposed unit he has said : 
“Its most characteristic feature is its Devonic element.” And : “If the 
fauna were considered by itself it would probably be pronounced a 
Scoharie or an Onondaga fauna without a moments hesitation, though 
there is a considerable Siluric element.” 
Taking the cut on p. 541 of the “Proceedings of the Albuquerque 
Meeting, (Fig. I. — Section of the Detroit river),” as setting forth the 
supposed relationship of the “Flat Rock, Anderdon coral limestone 
and Amlierstburg Dolomite,” the Flat Rock below, the Amlierstburg 
Dolomite above, the Anderdon between, then the “considerable 
Siluric element” ought to be very evident in the sandwiched Anderdon 
limestone in order that it should still persist in the overlying new-named 
Amlierstburg. But whereas the Siluric fauna characterizes the Flat 
Rock and the Amlierstburg Dolomite of the Detroit river bottom, it is 
characteristically absent from the Anderdon limestone beds. 
Moreover, the Anderdon beds do not extend across Detroit river from 
*Tlie Monroe Formation; Mich. Geolog. and Biolog. Survey, 1909, p 217. 
