Ironstones, condensed beds, and sequence stratigraphy of the Clinton Group (Lower Silurian) in its type area, central New York Nicholas Sullivan [
[email protected]] Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013 Carlton E. Brett [
[email protected]] Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013 Patrick McLaughlin [
[email protected]] Wisconsin Geological and Natural History Survey, 3817 Mineral Point Rd., Madison, WI 53705 ABSTRACT The fossiliferous and oolitic ironstones of the Clinton Group (Silurian, late Llandovery to early Wenlock) in central New York have inspired considerable interest since the early surveys of Eaton in the 1820s. Although these ores have never been mined on industrial scales, they were processed extensively up to the mid 1900s for oxides used in red paints. Three of these horizons, Westmoreland, "basal Dawes" or Salmon Creek, and Kirkland, will be examined and discussed on this excursion, with emphasis placed on their sedimentology, taphonomy, correlation, and regional significance in the context of depositional cycles. Recent work has recast these classic deposits in the context of sequence stratigraphy, wherein ironstones and related phosphatic and shelly deposits are viewed as condensed facies: the product of siliciclastic sediment starvation during periods of rapid transgression at the bases of small- and large -scale depositional sequences. These strata and the environmental conditions they represent will also be considered in the context of recently collected geochemical and geophysical data, which have implications for the correlation of these sections and their importance with regard to regional and global environmental changes and bioevents. B5-1 1. INTRODUCTION Although iron rich horizons in the sedimentary record are the subject of numerous studies, many critical questions remain concerning the processes of their formation (see Van Houten and Bhattacharyya, 1982; Kimberley, 1994 and references therein).