Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

Authigenic carbonate and the history of the global carbon cycle.

We present a framework for interpreting the carbon isotopic composition of sedimentary rocks, which in turn requires a fundamental reinterpretation of the carbon cycle and redox budgets over Earth's history. We propose that authigenic carbonate, produced in sediment pore fluids during early diagenesis, has played a major role in the carbon cycle in the past. This sink constitutes a minor compon...

Carbon accumulation in arid croplands of northwest China: pedogenic carbonate exceeding organic carbon

Soil carbonate (SIC) exceeds organic carbon (SOC) greatly in arid lands, thus may be important for carbon sequestration. However, field data for quantifying carbonate accumulation have been lacking. This study aims to improve our understanding of SIC dynamics and its role in carbon sequestration. We analyzed two datasets of SOC and SIC and their (13)C compositions , one with over 100 soil sampl...

Paired positive carbonate carbon isotope, organic carbon isotope, and oxygen isotope composition study across the Lower Mississippian positive carbon isotope excursion, southeastern Nevada, USA

Interpreting carbonate and organic carbon isotope covariance in the sedimentary record.

Many negative δ(13)C excursions in marine carbonates from the geological record are interpreted to record significant biogeochemical events in early Earth history. The assumption that no post-depositional processes can simultaneously alter carbonate and organic δ(13)C values towards more negative values is the cornerstone of this approach. However, the effects of post-depositional alteration on...

Seeking a geochemical identifier for authigenic carbonate.

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 ...