Earth and Atmospheric Sciences, Department of
Date of this Version
4-2009
Abstract
The Upper Pennsylvanian Indian Cave Sandstone (ICS) in southeastern Nebraska is herein reinterpreted as three multistory incised valley fills and one single-storey channel fill, altogether representing at least two different intervals of time. ICS lithosomes are linear bodies, as much as 2000 m wide and 30 m thick, incised into pre-existing cyclothems, and have relatively steep sides and flat bases. They include crudely fining-upwards successions of trough cross-bedded sandstones, interpreted as tidally-influenced fluvial deposits, overlain by upper estuarine heterolithic facies, with local coals, and a restricted trace fossil assemblage. The vertical facies succession suggests sediment accumulation in a regime of gradually increasing accommodation, i.e., during rising relative sea level. The basal erosion surfaces of ICS bodies can be traced out onto the adjacent interfluves where they correspond to well-developed paleosols, indicating sequence boundaries. Furthermore, the sequences defined herein can be correlated closely with recently published sequence stratigraphic frameworks from the region, suggesting that the ICS bodies record repeated, fifth-order (Milankovitch band), relative sea-level fluctuations of a minimum of 30 m during latest Pennsylvanian time Significantly, this estimate is half or less of those made by many other studies. Such a local quantification of relative sea-level change provides a critical constraint on eustatic sea-level fluctuation during the late Paleozoic Gondwanan Ice Age.
Comments
Published in Sedimentary Geology 216:1–2 (April 1, 2009), pp. 15–28; doi: 10.1016/j.sedgeo.2009.01.009 Copyright © 2009 Elsevier B.V. Used by permission.