30 Recent Advances in Paleoclimatology and Paleoceanography

Sunday, 25 September 2016
1:30 PM - 5:30 PM
Room 505

PERMIAN PALEOENVIRONMENT INDICATED BY STABLE CARBON AND OXYGEN ISOTOPE RECORDS OF BRACHIOPOD SHELLS FROM TIBET AND MONGOLIA

Paper number: 30-2
Program: Technical Sessions
Time: 1:45 PM – 2:00 PM

Authors

Abstract

We have studied the paleoenvironmental records for Permian Tibet (Selong) and southeastern Mongolia (Hovsugol Section and Dzhirem- Ula Section) region by analyzing the stable carbon and oxygen isotope records of fossil brachiopod shells collected from Tubet (N = 29) and Mongolia (N = 40). All brachiopod samples were thin sectioned and examined under the petrographic and cathodoluminescence microscopes for evaluation of shell preservation. A total of 130 and 90 isotopic analyses were performed on Tibet and Mongolia samples, respectively.

According to the characteristic observed under the cathodoluminescent microscope, average δ13C values of the well preserved samples (NL) are 4.7 ± 0.7‰ (N = 69; with the maximum value of 5.9‰) for Tibet and 4.3 ± 0.5‰ (N = 37; with the maximum value of 5.6‰) for Mongolia. These δ13C values are comparable to those of North America and Europe and reflecting the partial pressure of carbon dioxide and regional ocean circulation pattern for Permian.

The average δ18O values of the well preserved samples are -10.3 ± 3.2‰ for Tibet and -11.9 ± 5.2‰ for Mongolia. The maxima oxygen isotope values are respectively -2.2‰ and -3.9‰ for Tibet and Mongolia, whereas the minimum oxygen isotope values are -14.5‰ and -19.7‰, respectively. These maximum values are most likely reflecting the original environmental signals whereas these minimum oxygen isotope values may be attributed to diagenesis or melted glacial water input in this region.

Using the maximum oxygen isotope values, the estimated seawater temperature were 21°C and 29°C (assuming ice free δ18Oseawater of -1‰) or 26°C and 34°C (assuming modern δ18Oseawater of 0‰) for Tibet and Mongolia region, respectively. Cool temperature in Tibet whereas warm temperature in Mongolia is consistent with the Permian geography and climate model simulation. However, more well preserved samples are necessary to confirm preliminary result from this study.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-282618

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.