期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 116, 期 49, 页码 24433-24439出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1908783116
关键词
carbonates; carbon isotopes; chemostratigraphy; paleoclimate
资金
- NSF Division of Earth Sciences [1410317]
- Princeton Environmental Institute at Princeton University
- Geological Society of America Stephen G. Pollock Student Research Grant
- Evolving Earth Foundation
- High Meadows Foundation
- Sigma Xi Research Society
- Princeton Geosciences Student Research Fund
- Directorate For Geosciences
- Division Of Earth Sciences [1410317] Funding Source: National Science Foundation
In the past 3 billion years, significant volumes of carbonate with high carbon-isotopic (delta C-13) values accumulated on shallow continental shelves. These deposits frequently are interpreted as records of elevated global organic carbon burial. However, through the stoichiometry of primary production, organic carbon burial releases a proportional amount of O-2, predicting unrealistic rises in atmospheric pO(2) during the 1 to 100 million year-long positive delta C-13 excursions that punctuate the geological record. This carbon-oxygen paradox assumes that the delta C-13 of shallow water carbonates reflects the delta C-13 of global seawater-dissolved inorganic carbon (DIC). However, the delta C-13 of modern shallow-water carbonate sediment is higher than expected for calcite or aragonite precipitating from seawater. We explain elevated delta C-13 in shallow carbonates with a diurnal carbon cycle engine, where daily transfer of carbon between organic and inorganic reservoirs forces coupled changes in carbonate saturation (Omega(A)) and delta C-13 of DIC. This engine maintains a carbon-cycle hysteresis that is most amplified in shallow, sluggishly mixed waters with high rates of photosynthesis, and provides a simple mechanism for the observed delta C-13-decoupling between global seawater DIC and shallow carbonate, without burying organic matter or generating O-2.
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