ABSTRACT: Northern Appalachian Gas Possibilities: New Evidence from Geologic Setting of Columbia Gas Co. Finnegan No. 1 Dry Hole, North Easton, Washington Co., NY
Gou Baiying, J. E. Sanders, G. M. Friedman
The Finnegan test hole was drilled to a TD of 7758 ft. At a depth of 2764 ft (depth picked from dipmeter log), the hole encountered an overthrust, inferred to be the Orwell (or a closely analogous fault), along which closely folded Cambrian and Ordovician strata of the Champlain Valley carbonate-"shale" shelf succession have been displaced against low-dipping Upper Cambrian-Middle Ordovician strata of the Adirondack border "foreland" province. The westernmost major structural feature above this thrust is a large overturned anticline having in its core the Cambro-Ordovician shelf succession that Ruedemann mapped as the "Bald Mountain limestone" and that others have considered to be one or more large olistostrome blocks within the "shale." Included in this fold are the Aust n Glen Graywacke and Mr. Merino Chert.
Above the thrust, the hole cut folded shelf-sequence dolostones, limestones, shales/siltstones, and cherts but no graywackes. Below the thrust, the hole cut a normal succession of dark gray and black shales/siltstones (bottom at 5320; "Utica"?) gray to dark gray fine-textured silty limestones (bottom at 5824; "Trenton" through "Chazyan"?); light gray, fine- to medium-textured dolostones (bottom at 6430; "Little Falls"?); interbedded dolostones/sandstones (bottom at 7002; "Theresa"?); and sandstones/orthoquartzites (7002 to 7440; "Potsdam"? depth of Precambrian granitic-gneiss basement). The limestones at a depth of ^sim2 km show evidence of former depth of burial amounting to an estimated 10 km.
The strata of the Adirondack-border province are known to have been cut by steep normal faults. A newly recognized normal fault, inferred to be of post-lower Trenton, pre-"Utica" shale age, throws down on the east by an estimated 4000 ft. Faulting of this amount
is inferred to have been responsible for making available the various formations of the Cambro-Ordovician carbonates that supplied pebbles to the Rysedorph Hill Conglomerate. Structural traps for gas may lie hidden beneath the thick Middle-Upper Ordovician shales in a block-faulted "foreland" basin that extends an unknown distance eastward beneath the Appalachian-frontal overthrust.
AAPG Search and Discovery Article #90998 AAPG Eastern Section Meeting, London, Ontario, Canada, September 10-12, 1990