4Consulting Geologist, P.C. , P.O. Box 6128 ,Harrisburg, PA 17112

The deposition of the Black River, Trenton, and Utica groups (BrTU) reflects the overall drowning of southern Laurentia during formation of the Taconic Foreland basin. One phase of faulting and fracturing that led to mineralization and development of petroleum reservoirs may also to have been related, in part, to this same set of tectonic events. The BrTU history of deposition offers an opportunity to test this model.

Recent graptolite and conodont biostratigraphic results and geochemical fingerprinting of K-bentonites reveal that interactions between subsidence, sea level change, and sediment supply resulted in differences in BrT thickness of over an order of magnitude and differences in age of the base of the overlying shale cap of more than 5 MY. In the western Great Valley and eastern Valley and Ridge from northern VA-WV into PA and NJ and in the Hudson Valley, NY, Trenton facies are within the Phragmodus undatus Zone at their top and the overlying black shales are within the Climacograptus bicornis Zone – this despite passage across the PA reentrant and onto the NY Promontory. The Deicke and Millbrig (D-M) K-bentonites lie at or just above this contact. Across strike, in the central Valley and Ridge and lower Mohawk Valley, the Trenton facies are up-dip equivalents of the C. bicornis Zone shales, contain the D-M set, and are within the Plectodina tenuis Zone at their top. They are disconformably overlain by Utica Group rocks of the Corynoides americanus Zone. This pattern continues westward-- — the Trenton-Utica con tact steps upward repeatedly.

AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York