Stable carbon and oxygen isotope shifts in Permian seas of West Spitsbergen - Global change or diagenetic artifact?
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abstract
We performed petrographic, cathodoluminescence, electron-microprobe, and isotopic analyses of brachiopod shells from the Permian Kapp Starostin Formation in West Spitsbergen to reevaluate the >9 negative shift in 13 C and 18 O values reported in 1989 by M. Gruszczynski, S. Halas, A. Hoffman, and K. Malkowski. The 13 C and 18 O values within shells typically decrease with increasing luminescence, indicating diagenesis. Nonluminescent (NL) shell 13 C and 18 O values are 4.3 and 6.2 higher, respectively, than those of associated cements and matrix. For the same stratigraphie interval, 13 C and 18 O values of the NL shells are equal to, or substantially greater than, those reported by Gruszczynski et al. For the interval where those authors saw a 10 13 C shift, our mostly NL Spiriferella polaris shells only yield a 1.5 shift. Gruszczynski et al. reported a 9 18 O shift, whereas we observe almost none. Our results strongly suggest that the >9 isotopic shifts reported in Gruszczynski et al. are diagenetic artifacts. On the other hand, their Kazanian-Tatarian 13 C maximum of 7.5 is substantiated by our data. This Late Permian 13 C maximum represents the highest spiriferid brachiopod 13 C values in the Phanerozoic and, within stratigraphic uncertainty, correlates with the whole-rock 13 C maximum in East Greenland and northwestern Europe. The 13 C shift may reflect changes in global storage of organic carbon indicated by coal-volume changes in the Late Permian.
