Carboniferous and permian geologic timescale: State of the art, chronostratigraphic, biostratigraphic and radiometric calibration and integration

Category Paleontology and Stratigraphy
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Davydov, Vladimir۱; Schmitz, Mark۱; Chernykh, Valery۲; Crowley, Jim۱
Holding Date 15 September 2008

Significant progress has been made on the biostratigraphic and chronostratigraphic definition of the Carboniferous and Permian timescales since publication of the 2004 Geologic Time Scale, although each System possesses a different level of development. The base, top, and Mississippian-Pennsylvanian boundaries of the Carboniferous were defined in the last century.
The GSSP for the base of the Visean Stage is proposed and well on the way to be accepted. The bio-indexes to define the base of the Serpukhovian and Gzhelian Stages are accepted and potential candidates for the GSSP selections are searched or proposed. The definitions for the base of Moscovian and Kasimovian Stages are still debated.
The Guadalupian and Lopingian Series of the Permian System are defined and attributed with GSSPs. The proposed GSSP for the three Cisuralian stages (Sakmarian, Artinskian and Kungurian) are under current consideration by the Task/Working Group. It is considered realistic to complete entire International Permian timescale at the stadial level before GTS 2010.
Bases and tops of both Systems possess solid U/Pb radiometric ages (Trapp et al., 2004; Ramezani et al., 2006; Mundil et al., 2004). The most advanced high-precision (≤ 0.1%) ID-TIMS U-Pb zircon dating methods have been applied to numerous volcanic ashes found and/or collected during the last decade in the southern Urals, Donets Basin, and Northern Germany. The radiometric ages of the majority of stage boundaries are 3-5 Ma older then was previously proposed based on 40Ar/39Ar and SHRIMP U-Pb zircon methods. The analyzed samples have been collected in biostratigraphically well-constrained successions characterized with major fossils such as conodonts, foraminifera, and ammonoids. All ages are being quantitatively integrated into the time scale using CONOP, RASC and GraphCor tools.
In addition, the definition of a highly precise and accurate seawater Sr isotope chemostratigraphy for portions of the Moscovian-Kungurian has been initiated with the study of biogenic apatite of conodonts in the southern Urals sections calibrated by intrastratified ash bed ages. This Sr isotope curve is calibrated against U/Pb zircon ash bed ages from the same stratigraphic sections, and thus can be used as a high-precision geochronological tool particularly for the Cisuralian.
The majority of original data including biostratigraphy, U/Pb and Sr/Sr values from type and key-sections that were involved in integration processes are already archived or will be archived in the open web-accessible database system.
The highly integrated Late Paleozoic Timescale can now provide a basis for global marine-nonmarine correlation and for better understanding climatic (ice house - green house transition) and tectonic (Pangaea integration) events. This study were funded by the Sedimentary Geology and Paleontology program of the NSF (grants EAR-0418703 EAR-0510876 and EAR-0545247).