Geological Society of America

19 Pander Society Symposium (Posters)

Thursday, 4 April 2002
8:00 AM - 12:00 PM

MAPS OF CONODONT CAI AND %RO THERMAL MATURITY PATTERNS FOR ORDOVICIAN AND DEVONIAN ROCKS OF NEW YORK AND PENNSYLVANIA

Paper number: 19-8
Program: SYMPOSIA SESSIONS
Time: 8:00 AM – 12:00 PM

Authors

John E. Repetski Presenting Author
U.S. Geol Survey, Reston, VA
D. J. Weary
U.S. Geol Survey, Reston, VA
R. T. Ryder
U.S. Geol Survey, Reston, VA
R. E. Nyahay
New York State Geol Survey, Albany, NY
J. A. Harper
Department of Conservation and Nat Rscs, Pittsburgh, PA
M. H. Trippi
U.S. Geol Survey, Reston, VA

Abstract

Based on approximately 200 new data points, new conodont color alteration index (CAI) and vitrinite reflectance (%Ro) maps are presented for the Ordovician and Devonian of New York and Pennsylvania, as part of a larger study of the thermal maturation history of the central Appalachian basin. These new maps complement those constructed in the late 1970's by Anita Harris and colleagues - the new maps rely chiefly on subsurface data from the Appalachian plateau province of the Appalachian basin, whereas the previous maps relied chiefly on outcrop samples from the more easterly Valley and Ridge province. These new maps encompass the area of historical deep oil and gas drilling in the Appalachian basin and include the region of recent increased deep drilling aimed at Ordovician Black River and Trenton reservoirs.

The two stratigraphic intervals for the new maps - Middle and Upper Ordovician and Lower and Middle Devonian - were chosen for several reasons: 1) they are the target reservoir zones of much of the oil and gas exploration and drilling in this region; 2) they are stratigraphically near the probable source-bed formations for the Devonian and Middle/Upper Ordovician; and 3) they are in carbonate rock formations, which give a reasonable probability of recovery of conodonts from small samples of drill cuttings. The new data are presented at a larger map scale than previously and they may delineate more precisely regions related to tectonic processes favorable for oil and gas preservation. In general, the new CAI isograds are shifted westward from the extrapolated pattern of the previous maps. Other local to regional variations in the new patterns can be attributed to extensional tectonism related to the Rome trough and the Scranton gravity high, and to possible effects of later igneous intrusive bodies.