A century ago, on April 15, 1836, the formation of a “geological survey of the State of New-York” was authorized by its legislature. Timothy Conrad began field work the following June in the Mohawk Valley, describing in his first report the “Blue Foetid Limestone and Shales of Trenton-Falls.” It is the present purpose, first, to review the study of these sediments prior to Conrad’s naming them and trace the developments during the century that has followed; second, to define and give brief descriptions of the subdivisions of the Trenton group, the upper part of the Mohawkian series of the Ordovician system; finally, to summarize interpretation of the distribution and changes in the sediments.
The writer has studied the Trenton group for a number of years; a grant from the Penrose Bequest of the Geological Society permitted re-study of the entire problem during the summer of 1935. The fauna of . . .