title: Seeking a geochemical identifier for authigenic carbonate.
abstract: Authigenic carbonate was recently invoked as a third major global carbon sink in addition to primary marine carbonate and organic carbon. Distinguishing the two carbonate sinks is fundamental to our understanding of Earth's carbon cycle and its role in regulating the evolution of atmospheric oxygen. Here, using microscale geochemical measurements of carbonates in Early Triassic strata, we show that the growth of authigenic carbonate follows a different trajectory from primary marine carbonate in a cross-plot of uranium concentration and carbon isotope composition. Thus, a combination of the two geochemical variables is able to distinguish between the two carbonate sinks. The temporal distribution of authigenic carbonates in the Early Triassic strata suggests that the increase in the extent of carbonate authigenesis acted as a negative feedback to the elevated atmospheric CO2 concentration.
authors.affiliation: CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Ming-Yu
authors.initials: MY
authors.lastname: Zhao
authors.affiliation: CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Yong-Fei
authors.initials: YF
authors.lastname: Zheng
authors.affiliation: CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Yan-Yan
authors.initials: YY
authors.lastname: Zhao