New High-Precision ID-TIMS U-Pb Zircon Constraints from the Durations of Pennsylvanian - Lower Permian (Cisuralian) Stages

Mark D. Schmitz, Vladimir I. Davydov, Walter S. Snyder, and Clyde J. Northrup
Department of Geosciences, Boise State University, Boise, ID

Stratigraphic sections of the Southern Urals containing abundant and well-preserved fauna for precise biostratigraphic correlation and common instratified volcanic ash beds continue to provide opportunities to calibrate Pennsylvanian and Lower Permian (Cisuralian) time through high-precision ID-TIMS U-Pb zircon geochronology. A dozen preliminary zircon ages have been obtained for ash beds from the deep-water sections at Usolka and Dal’ny Tulkas, in the northern Ural sub-basin. These ashes are interbedded in strata spanning the uppermost Moscovian Stage of the Middle Pennsylvanian to the base of the Artinskian Stage of the Cisuralian. The host sections have been recently proposed as Global Boundary Stratotype Sections and Points (GSSPs) for the base of the Ghzelian (Usolka) and Artinskian (Dal’ny Tulkas) Stages, and the biostratigraphy of these sections is easily correlated to the accepted or proposed GSSPs at Aidaralash (basal Asselian) and Kondurovsky (basal Sakmarian), in the southern basin. In this presentation, we will: 1) present new age constraints on the duration of the Sakmarian and Asselian Stages of the Cisuralian, and illustrate their utility in calibrating a new, highly resolved seawater Sr isotope curve for global chemostratigraphic correlation; and 2) present new age constraints on the duration of the Kasimovian and Ghzelian Stages of the Upper Pennsylvanian, and discuss their implications for global correlation and the tempo and drivers of cyclothemic sedimentation during the Late Carboniferous icehouse.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas