Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene-Eocene Thermal Maximum record from central China

The carbon isotope excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM) has been recognized for the first time in the micritic carbonate, total organic carbon (TOC) and black carbon (BC) contained within the lacustrine sediments from the Nanyang Basin, central China. The remarkably large excursion (similar to-6 parts per thousand) in the delta C-13(TOC) and delta C-13(BC) values is possibly attributable to increased humidity and elevated pCO(2) concentration. The similar to-4 parts per thousand CIE recorded in the delta C-13(calcite), reflecting the average isotope change of the watershed system, is consistent with that observed in planktonic foraminifera. This correspondence suggests that the true magnitude of the carbon isotope excursion in the ocean-atmosphere system is likely close to -4 parts per thousand. The similar to 10 m excursion onset in our multi-proxy delta C-13 records demonstrates that the large input of C-13-depleted carbon into the ocean-atmosphere system was not geologically instantaneous. Despite difference and somewhat smoothness in detailed pattern of the CIE due to localized controls on different substrates, inorganic and organic delta C-13 data generally depict a gradual excursion onset at least over timescales of thousands of years. In addition, continental temperature reconstruction, based on the distribution of membrane lipids of bacteria, suggests a warming of similar to 4 degrees C prior to the PETM and similar to 7 degrees C increase in temperature during the PETM. The temperature data are overall similar in pattern and trend to the delta C-13 change across the PETM. These observations, combined with pre-CIE warming, are in line with the idea that C-13-depleted carbon release operated as a positive feedback to temperature, suggesting supply from one or more large organic carbon reservoirs on Earth's surface. (C) 2014 Elsevier B.V. All rights reserved.