THE MOHAWK VALLEY DRILL CORE BONANZA:NEW INSIGHTS RELATING TO THE POST-SAUK SUCCESSION AS SEEN THROUGH CORE AND OUTCROP PERSPECTIVES

A major cache of private sector drill cores, discovered and reposited at the NY State Survey, has been measured. Topmost Sauk and post-Sauk strata (inclusive of Black River, Trenton, Utica, and Schenectady divisions) have been examined in their entirety for 53 Mohawk Valley core sites. The Grenville – basal Sauk nonconformity contact is present in, at least, 37 of these cores. An unusually thick (19m) Black River Limestone succession is developed in a core at Riceville, immediately southeast of the Noses Fault north of Gloversville; this succession displays internal and bounding discontinuities and differentiation into lower “Lowville-type” and upper “Watertown-type” divisions. Moreover, a prominent, 15 cm-thick, K-bentonite bed in mid-succession could correlate to the well-known Deike or Millbrig ashes. In the Broadalbin and Gloversville cores, southeast of Riceville, micrite clast breccias occur between Sauk dolostones and the overlying Glens Falls Limestone; these breccias appear to link NW into the thicker, down-dropped Riceville Black River section. Differentially thicker Napanee and higher Trenton units above the Black River at Riceville further support the idea of a down-to-the-west block rotation in this area. Spectacular, bitumen-filled vertical burrows, as seen at Ingham Mills, occur below discontinuities in the Black River interval in the Indian Castle and Riceville cores. Numerous cores in the Middleville – Herkimer area allow linkage of key medial Trenton and Utica limestones, discontinuities, and K-bentonite beds from outcrop into the adjacent subsurface. A core from East Herkimer closes a vexing outcrop gap below the newly recognized Jacksonburg Bed and shows that it is a condensed, basin margin facies of the basal Rust Limestone. Three cores extend into the Schenectady Formation. One of these, displays 300 m of turbiditic siltstone and shale deposits; this long section dwarfs Schenectady outcrops in the medial Mohawk Valley area, and provides new insights regarding the nature and timing of Taconian basin filling.