Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Schieber, J. Articles by Riciputi, L. Search for Related Content GeoRef GeoRef Citation

Pyrite ooids in Devonian black shales record intermittent sea-level drop and shallow-water conditions

¹ Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, USA
² Chemical and Analytical Services Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6365, USA

Upper Devonian black shales of the eastern United States contain in places unusual beds of pyrite ooids. Textural and geochemical studies show that these originated as chamositic iron ooids that were replaced by pyrite during early diagenesis. Pyrite mimics the laminated texture of the precursor grain, yet inclusions of silicate minerals and instances of partial replacement reveal the secondary nature of the pyrite. Pyrite ooids occur above erosion surfaces that are considered sequence boundaries because of large lateral extent. Chamositic precursor ooids indicate an oxygenated water column and wave interaction with seafloor sediments at the time of their formation. This scenario agrees with earlier work that stipulates that erosion surfaces in Devonian black shales reflect lowering of sea level that allowed wave reworking and erosion of earlier-deposited black shales. Pyrite ooid beds thus furnish direct evidence of significant sea-level drops during the accumulation of Upper Devonian black shales in eastern North America.

Key Words: black shale • sea level • sequence boundary • pyrite ooids • chamosite • ironstone

This article has been cited by other articles:

				T. J. Algeo and J. B. Maynard Trace-metal covariation as a guide to water-mass conditions in ancient anoxic marine environments Geosphere, October 1, 2008; 4(5): 872 - 887. [Abstract] [Full Text] [PDF]

				J. Schieber and L. Riciputi Pyrite and Marcasite Coated Grains in the Ordovician Winnipeg Formation, Canada: An Intertwined Record of Surface Conditions, Stratigraphic Condensation, Geochemical "Reworking," and Microbial Activity Journal of Sedimentary Research, September 1, 2005; 75(5): 907 - 920. [Abstract] [Full Text] [PDF]