332-9 Milankovitch and Millennial-scale Cycles in the Frasnian-Famennian Beaver Meadow Member of the Hanover Formation and Overlying Dunkirk Formation, Upper Devonian, Western New York State

Abstract:

The Frasnian-Famennian boundary marks the end of the Kellwasser Crisis, one of the “Big 5” mass extinctions.  The boundary is recognized at the top of the Pt. Gratiot Bed, the Upper Kellwasser Bed equivalent, in the Beaver Meadow Member of the Hanover Formation in western New York State.  Three drill cores, two in the valley of Eighteenmile Creek and one in the Buffalo Creek Valley, through the Beaver Meadow Member, in an east to west transect where the Pt. Gratiot Bed and the Beaver Meadow Member thicken eastward, were sampled at 1 cm intervals and analyzed for magnetic susceptibility (MS).  Fourier Transform Analysis resolved two distinct cycles at 0.4-0.6 cycles per meter and 2 cycles per meter that correspond to Milankovitch band obliquity and precession cycles.  Millennial-scale cycles are superimposed on the longer cycles.  In the overlying Dunkirk Formation, which marks the onset of the IIE transgressive cycle, the MS values are lower and cycles are muted, but detectable in the same frequencies.

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