CARBON SEQUESTRATION POTENTIAL OF ALTERED PROTEROZOIC BASEMENT ROCKS, NORTHERN APPALACHIAN BASIN, NEW YORK STATE

Elimination of carbon emissions from coal-fired electrical generation in New York State will require capture and sequestration of 1.3 million U.S. tons of carbon dioxide annually. The Paleozoic sedimentary strata of the northern Appalachian Basin offer some potential for sequestration, but in general, the rocks are porosity-challenged. In addition, future development of gas from Ordovician (Utica) and Devonian (Marcellus) shale must be considered when targeting units for carbon sequestration (CS). Significant and relatively unexplored potential for CS may exist in altered basement rocks that lie beneath the Paleozoic sequence. Petrologic and geochemical analyses of core and outcrop from the Mohawk Valley and St. Lawrence Lowlands, near the edge of the Paleozoic cover, document significant porosity and permeability in altered basement rocks beneath the ‘Grand Unconformity’. Alteration of Grenville basement occurred during early Paleozoic weathering prior to burial, and during later burial diagenesis when circulating basinal fluids interacted with porous and permeable basement rock. Down-core geochemical profiles in the basement rock document K-uptake due to diagenetic illite and K-feldpar growth. However, additional porosity and permeability developed in the basement due to diagenetic alteration of plagioclase and ferromagnesian minerals. Extensive pre-Paleozoic fracture networks in basement facilitated both meteoric and later diagenetic burial alteration. In the western St. Lawrence Lowlands, a second episode of meteoric alteration occurred when upper Cambrian Potsdam Formation sands were exposed above sea level prior to the early Ordovician flooding event that deposited the Theresa Formation. In this area, significant meteoric alteration of basement occurred beneath an active freshwater aquifer system, leaving deep, porous regolith or ‘granite wash’. This area of pronounced basement alteration may be present in the subsurface in western New York State, where depths are sufficient to sequester carbon dioxide.