TY - JOUR
T1 - Isotopic records of brachiopod shells from the Russian Platform - Evidence for the onset of mid-Carboniferous glaciation
AU - Mii, Horng Sheng
AU - Grossman, Ethan L.
AU - Yancey, Thomas E.
AU - Chuvashov, Boris
AU - Egorov, Alexander
N1 - Funding Information:
We thank John Carter for help with brachiopod identification, Renald N. Guillemette for technical assistance on EPMA, and Qiwei Wang for help with the SEM. This manuscript benefited from the comments of Peter Bruckschen and Tom Crowley, and reviews by Christophe Lécuyer and Prasada Rao. Thanks also go to the Department of Geology and Geophysics, Texas A&M University for partial support of EPMA, and the Electron Microscopy Center at Texas A&M University for providing the SEM facilities. Funding was provided by National Science Foundation grant EAR-9304815. This study was conducted under the auspices of the Paleoecology Research Program at Texas A&M University.
PY - 2001/5/1
Y1 - 2001/5/1
N2 - We performed isotopic analyses of Carboniferous brachiopod shells from the Russian Platform to examine global and regional environmental change along the western and eastern margins of Laurussia during the formation of Pangea, and specifically to examine the isotopic evidence for the onset of mid-Carboniferous glaciation. Shell preservation was evaluated from shell microstructure, cathodoluminescence, trace element content and isotopic comparison with matrix material. Most interior nonluminescent (NL) prismatic shell appears to be chemically well preserved as indicated by low to undetectable Si, Al, Fe and Mn contents. With minor exception, NL shell δ 13C and δ 18O values are higher than those of corresponding cements and matrix. The δ 13C record for the Russian Platform clearly shows a 3‰ increase (from 2.4 ± 0.7‰ to 5.5 ± 0.6‰) in the Serpukhovian or Early Bashkirian. This shift was first reported by Popp et al. [Popp, B.N., Anderson, T.F., Sandberg, P.A., 1986. Brachiopods as indicators of original isotopic compositions in some Paleozoic limestones. Geol. Soc. Am. Bull. 97, 1262-1269.], but had not been documented for a single region. Widespread occurrence of high δ 13C values in the Late Carboniferous support the interpretation of Popp et al. with regard to this shift as a record of increased burial of organic carbon. North American sections show a mid-Carboniferous δ 13C shift of only ∼ 1.5‰. We hypothesize that the reduced δ 13C shift reflects enhanced upwelling on the epicontinental seas of North America after the closing of the seaway between Laurussia and Gondwana. The δ 18O record for the Russian Platform shows a 1.8‰ increase in the mid-Carboniferous correlative with increased occurrence of glacial sediments and a drop in sea level. As a first approximation, ice volume calculations suggest that ∼ 0.7‰ of the mid-Carboniferous δ 18O shift is due to changes in seawater δ 18O, and ∼ 1.1‰ is due to 5°C cooling. Concurrent positive δ 13C and δ 18O shifts provide evidence for a relationship between mid-Carboniferous glaciation and burial of organic carbon, presumably through changes in atmospheric CO 2, levels.
AB - We performed isotopic analyses of Carboniferous brachiopod shells from the Russian Platform to examine global and regional environmental change along the western and eastern margins of Laurussia during the formation of Pangea, and specifically to examine the isotopic evidence for the onset of mid-Carboniferous glaciation. Shell preservation was evaluated from shell microstructure, cathodoluminescence, trace element content and isotopic comparison with matrix material. Most interior nonluminescent (NL) prismatic shell appears to be chemically well preserved as indicated by low to undetectable Si, Al, Fe and Mn contents. With minor exception, NL shell δ 13C and δ 18O values are higher than those of corresponding cements and matrix. The δ 13C record for the Russian Platform clearly shows a 3‰ increase (from 2.4 ± 0.7‰ to 5.5 ± 0.6‰) in the Serpukhovian or Early Bashkirian. This shift was first reported by Popp et al. [Popp, B.N., Anderson, T.F., Sandberg, P.A., 1986. Brachiopods as indicators of original isotopic compositions in some Paleozoic limestones. Geol. Soc. Am. Bull. 97, 1262-1269.], but had not been documented for a single region. Widespread occurrence of high δ 13C values in the Late Carboniferous support the interpretation of Popp et al. with regard to this shift as a record of increased burial of organic carbon. North American sections show a mid-Carboniferous δ 13C shift of only ∼ 1.5‰. We hypothesize that the reduced δ 13C shift reflects enhanced upwelling on the epicontinental seas of North America after the closing of the seaway between Laurussia and Gondwana. The δ 18O record for the Russian Platform shows a 1.8‰ increase in the mid-Carboniferous correlative with increased occurrence of glacial sediments and a drop in sea level. As a first approximation, ice volume calculations suggest that ∼ 0.7‰ of the mid-Carboniferous δ 18O shift is due to changes in seawater δ 18O, and ∼ 1.1‰ is due to 5°C cooling. Concurrent positive δ 13C and δ 18O shifts provide evidence for a relationship between mid-Carboniferous glaciation and burial of organic carbon, presumably through changes in atmospheric CO 2, levels.
KW - Brachiopods
KW - Carboniferous
KW - Glaciation
KW - Isotopes
KW - Paleoclimate
KW - Platform
KW - Russian
UR - http://www.scopus.com/inward/record.url?scp=0035020206&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035020206&partnerID=8YFLogxK
U2 - 10.1016/S0009-2541(00)00366-1
DO - 10.1016/S0009-2541(00)00366-1
M3 - Article
AN - SCOPUS:0035020206
SN - 0009-2541
VL - 175
SP - 133
EP - 147
JO - Chemical Geology
JF - Chemical Geology
IS - 1-2
ER -