『Abstract
The carbon (δ13Corg) 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 δ13Corg.
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 δ13Corg
may be ascribed to an abrupt change in shallow-water microbial
communities, which differed in composition from contemporaneous
deep-water communities.』
Introduction
Carbon and nitrogen isotope profiles
Marine source of isotope signals
Marine nitrogen cycle during the P-Tr transition
Global carbon cycle during the P-Tr transition
Nature of microbialite community
Acknowledgments
References cited