Abstract: Carbonate Diagenesis and Dolomitization of Cambro-Ordovician (Sauk Sequence) Platform Strata in Central New York

Shruti S. Philips, Gerald M. Friedman

This study focuses on the diagenetic history of the Sauk Sequence carbonates in an attempt to decipher the timing, processes and stages of dolomitization. These Lower Paleozoic platform carbonates, exposed in the Mohawk Valley and Saratoga Springs area in central New York, were deposited in a shallow continental shelf environment; their strontium-isotopic composition is consistent with that of Late Cambrian seawater. This sequence is distinguished here as the Upper Cambrian Little Falls, Galway and Hoyt formations and the Lower Ordovician Gailor and Tribes Hill formations.

Outcrop studies reveal that the bulk of this sequence is dolomitized. The Little Falls and Galway formations are composed of interbedded dolostones and sandstones displaying herringbone cross-strata, planar and domal stromatolites, intraclasts, bird's eye structures and local chert horizons. The Hoyt formation is extremely fossiliferous with columnar, domal and planar stromatolites and trilobites. The younger Gailor and Tribes Hill formations display planar stromatolites, chert horizons, solution-collapse breccia, bird's eye vugs, the strata becoming increasingly fossiliferous towards the top. The Knox unconformity lies atop the lower Ordovician in the Mohawk Valley. A peritidal environment of deposition is inferred for the entire sequence.

Plane-Light and Cathodoluminescence petrography have revealed different types of dolomite generations including several types of zoned dolomites, unzoned red luminescent dolomite, nonluminescent dolomite, saddle dolomite and dedolomite. The diagenetic history of the entire sequence clearly includes multiple episodes of dolomitization, calcite cementatation, chertification and karstification. Detailed petrographic and geochemical studies of these carbonates are in progress with the aim of understanding better the diagenetic processes involved in their evolution.

AAPG Search and Discovery Article #90954©1995 AAPG Eastern Section, Schenectady, New York