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Carbon and Strontium Isotopes of Late Palaeozoic Marine Carbonates in the Upper Yangtze Platform, Southwest China
Author(s) -
Sijing Huang,
Shaohua Zhou
Publication year - 1997
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.1997.tb00369.x
Subject(s) - permian , geology , carboniferous , paleozoic , isotopes of strontium , devonian , strontium , paleontology , late devonian extinction , sedimentary rock , isotopes of carbon , geochemistry , conodont , total organic carbon , biostratigraphy , chemistry , environmental chemistry , structural basin , organic chemistry
238 marine carbonate samples were collected from seven sedimentary sections of the entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Platform, southwest China. Based on the absence of cathodoluminescence and very low Mn (generally < 50 ppm) contents of the samples, it is thought that they contain information on the original sea water geochemistry. The results of isotopic analyses of these samples are presented in terms of δ 13 C and 87 Sr/ 86 Sr ratios versus geological time. The strontium data, consistent with other similar data based on samples from North America, Europe, Africa and other areas in Asia, support the notion of a global consistency in strontium isotope composition of marine carbonates. The strontium data exhibit three intervals of relatively low 87 Sr/ 86 Sr ratios in the late Middle Devonian to early Late Devonian, Early Carboniferous and Early Permian, corresponding to global eustatic high sea level stands. The lowest 87 Sr/ 86 Sr ratio recorded in the Late Permian was probably caused by substantial basalt eruptions in the Upper Yangtze Platform at the time. Three corresponding periods of relatively high δ 13 C values at roughly the same time intervals were caused by a relatively high rate of accumulation of organic carbon during sea level rises at these times. The deposition of coal was probably responsible for the increase of sea water δ 13 C at other times. The δ 13 C values drop dramatically near the Devonian/Carboniferous, Carboniferous/Permian and Permian/Triassic boundaries, consistent with other similar data, which further support the notion that geological time boundaries are associated with mass extinction and subsequent rejuvenation.