REVISION OF THE STRATIGRAPHY OF THE EIFELIAN-GIVETIAN HAMILTON GROUP IN NEW YORK STATE: AN UPDATE SINCE THE SUMMARY OF RICKARD'S 1975 DEVONIAN CORRELATION CHART

The Middle Devonian Hamilton Group is one of the most well studied intervals within the NYS Devonian section. The combination of numerous exposures and a highly diverse, well preserved fauna has led to this interval being used to test numberous stratigraphic and evolutionary hypotheses over the last 50 years. The Hamilton Gp., named by Vanuxem in 1840, revised by Cooper in the early 1930s, and refined extensively since, includes the Union Springs, Oatka Creek-Mount Marion, Skaneateles, Ludlowville, Panther Mountain, and Moscow fms.; the Union Springs, Oatka Creek and Mount Marion fms. make up the Marcellus subgroup. The Hamilton Gp. is exposed in two primary outcrop belts in NYS: a) an east-west trending belt from Buffalo to the Helderbergs, with extensive areas of exposure in the Finger Lakes region, is arrayed roughly perpendicular to strike of the Catskill Delta spanning distal deep-water facies in the west to proximal terrestrial facies in the east; b) a second set of exposures trend NNW-SSW from the Helderbergs to Port Jervis arrayed roughly parallel to strike of the Catskill Delta consisting largely of proximal/terrestrial facies. As currently defined the formations of the Hamilton Group equate to third-order depositional cycles each containing numerous smaller-scale cycles.

Major revisions since the publication of the 1975 NYS Devonian stratigraphic chart in 1975 that that will be reviewed in this talk include: increased understanding of biostratigraphy through the interval; increased understanding of depositional cyclicity through the interval; examination of patterns of faunal turnover; investigation of the East Berne Member; reevaluation of the Mottville Mbr. and small-scale TSTs in the Skaneateles Fm.; revision of the stratigraphy and investigation of biofacies within the Centerfield Member; bed-level correlation over large areas and across facies in all units; reevaluation of the Portland Point Member; correlation of small-scale depositional cycles within the Ludlowville and Moscow fms.; and in-depth investigation of the stratigraphy at the top of the Moscow Fm. Areas ripe for further investigation will also be discussed including examination of the Panther Mt. Fm., correlation into the terrestrial succession, examination of the area of transition between the Mt. Marion and Oatka Creek fms., etc.