EASTERN NEW YORK MIDDLE DEVONIAN NEAR SHORE BIOFACIES: CONTROLS ON BIOFACIES DISTRIBUTION IN AREAS WITH VARYING SEDIMENTARY INPUT

The Middle Devonian marine sediments of the Hamilton Group of New York State contain a well-preserved invertebrate fauna exposed in a large number outcrops ranging from shallow-water, well-oxygenated, coarse-grained facies in the east to deep-water, fine-grained dysoxic facies in the west. Recent studies of the distribution of biofacies within the Hamilton Group have shown a direct relation to water depth as a major control in western-central New York. These studies were conducted in areas with relatively constant rates of sediment supply. However, the controls on biofacies distribution in areas with varying rates of sediment input are as yet poorly understood.

The current study aims to tackle this problem by examining sections in eastern New York State close to the delta front through the upper portions (Mount Marion Formation) of the Marcellus subgroup. The Marcellus subgroup of the Hamilton Group was deposited at the onset of tectophase II of the Acadian Orogeny in a rapidly subsiding basin, known as the Appalachian Foreland Basin, on the eastern margin of what is now the North American continent. Sequences of gradually coarsening-upward sediments were deposited preserving deposits along the full suite of depositional environments in eastern New York State.

Samples have been collected through the Mount Marion Formation from level spanning different portions of the sea level sequences with varying rates of sediment input. Statistical methods such as De-trended Correspondence Analysis (DCA) and Analysis of Similarity (ANOSIM) will be utilized to describe trends of biofacies change throughout the various outcrops. Stratigraphic and lithological data taken at all sections and will be used to describe the paleoenvironments as related to sea level change and varying sediment input rates.