CO-OCCURRENCE OF MICROSPHERULES AND CONCRETION BEDS IN DEVONIAN SHALE BEDS OF WESTERN NEW YORK

Abundant microspherules associated with carbonate concretion beds have been discovered at the contact of the Upper Devonian Rhinestreet and overlying Angola formations of on Eighteenmile Creek of Western New York. Similar objects have also been recovered from near the contact of the Cashaqua Formation and overlying Rhinestreet Formation, also on Eighteenmile Creek. The latter occurrence is associated with an abrupt negative stable carbon isotope excursion that appears to define the termination of the Upper Devonian punctata event in the Appalachian Basin. Microspherules have also been collected from shale and concretions near the Rhinestreet-Hatch contact in the Genesee River Valley. Most spherules are spheroidal or teardrop in shape and range in size from approximately 150 to >500 microns in diameter. Nearly opaque dark and exceptionally clear microspherules occur in both concretions and host shale. However, microspherules were found in higher concentrations within the carbonate concretions; up to several thousand per gram. Evidence of transport is lacking. Electron dispersive microscopy results show that both light and dark glass spherules are Si-Na rich, which differs markedly from the host shale chemical composition. Their origin is still in question as these spherules can be considered either natural (biological or mineral) or an artificial product (fly-ash or contaminants of local manufacturing). However, timing and proximity do not eliminate these as potential evidences for the known Devonian Alamo, Charlevoix or Siljan impact events but may also give credence to the suspected impact event at Panther Mountain, New York.