• journal_title：Geology
• Contributor：Genming Luo ; Yongbiao Wang ; Thomas J. Algeo ; Lee R. Kump ; Xiao Bai ; Hao Yang ; Le Yao ; Shucheng Xie
• Publisher：Geological Society of America
• Date：2011-
• Format：text/html
• Language：en
• Identifier：10.1130/G32024.1
• journal_abbrev：Geology
• issn：0091-7613
• volume：39
• issue：7
• firstpage：647
• section：Articles

The carbon (δ¹³C_org) and nitrogen (δ¹⁵N) isotopic compositions of bulk organic matter were analyzed in two high-resolution Permian-Triassic transitional sections containing microbialite in south China. The results from these shallow-marine sections show that an abrupt negative shift in δ¹⁵N, from ∼+3‰ to ∼0‰, occurred immediately after the latest Permian mass extinction (LPE) in both sections, concurrent with a distinct negative shift in δ¹³C_org. The persistently low values of δ¹⁵N suggest that, following the LPE, microbial nitrogen fixation became the main source of biologically available nitrogen in the Nanpanjiang Basin and perhaps over a broader region of the eastern Paleotethys Ocean. Enhanced N fixation is probably indicative of the prevalence of stratified anoxic water masses characterized by intense denitrification and/or anaerobic ammonium oxidation at the time. Perturbation of the marine nitrogen cycle might have contributed to high temperatures following the main marine mass extinction through the release of the greenhouse gas N₂O. The sharp declines in δ¹⁵N and δ¹³C_org may be ascribed to an abrupt change in shallow-water microbial communities, which differed in composition from contemporaneous deep-water communities.