--> Abstract: Sr Isotope Sstratigraphy of the Early Permian Cisuralian Epoch (Artinskian-Kungurian Stages) from Laibin, China, by K. Tierney, M. Saltzman, J. Yan, K. A. Foland, J. Linder, A. Munnecke, and B. D. Cramer; #90078 (2008)

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Sr Isotope Sstratigraphy of the Early Permian Cisuralian Epoch (Artinskian-Kungurian Stages) from Laibin, China

Kate Tierney2, Matthew Saltzman2, Jiaxin Yan1, Kenneth A. Foland2, Jeff Linder2, Axel Munnecke3, and Bradley D. Cramer2
1Chinese University of Geosciences, Wuhan, China
2Ohio State University, Columbus, OH
3Institut für Paläontologie der FAU Erlangen, Erlangen, Germany

Carbonate samples have been analyzed for 87Sr/86Sr from the Tieqaio section at Laibin, China. The section analyzed spans the Artinskian (pamrinia and tschernyschewi fusulinids) through Kungurian Misellina claudiae fusulinid zone. Laibin is thick and well constrained by fusulinids, with conodont samples currently being processed that will further increase the potential for intercontinental correlations. The 87Sr/86Sr values fall steadily from 0.707668 in the Artinskian to 0.707371 in the Kungurian. The decreasing trend is consistent with the overall Permian (Cisuralia-Guadalupian) drop in the curve of Korte et al (2006), and data through the mid-Sakmarian reported by Needham et al (2006). Korte et al. (2006), however, show a considerable spread of values for the Kungurian, which they consider “bad” brachiopod data due to stratigraphic uncertainty. Thus, our new data resolve the Sr isotope trend for a key gap in the “good” data of Korte et al (2006; Figure 4).

Sr concentrations in our samples range from 150 to 1200 ppm, with an average of 550 ppm. Korte et al (2006) considered samples with greater than 400 ppm Sr as well preserved (“good”). Furthermore, Korte et al analyzed a brachiopod from the Laibin section (sample ch33), which is at precisely the same level from which one of our samples was analyzed. The difference in Sr isotope values between their brachiopod sample and our micritic limestone is 0.000003 (0.707368 vs. 0.707371).

The overall Sr isotope drop in the Permian (Cisuralia-Guadalupian) has been attributed to increased continental aridity and a diminishing riverine flux of radiogenic strontium to the oceans. This is consistent with lithologic evidence, including evaporite deposits and red beds. At the same time, the glaciation in the Southern Hemisphere was weakening, and the Neotethys was opening which could also contribute non-radiogenic Sr.

 

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