Contributions of soot to δ13C of organic matter in Cretaceous lacustrine deposits, Gyeongsang Basin, Korea: Implication for paleoenvironmental reconstructions

초록

This study reports that soot carbon (SC) derived from biomass burning is an important constituent of total organic carbon (TOC) (30-90%) in two Cretaceous lacustrine deposits (Middle Albian Jinju Formation and Early Cenomanian Banyaweol Formation) of the Gyeongsang Basin, Korea and that SC contributed significantly to the carbon isotope composition (delta C-13) of the TOC delta C-13 of the TOC and delta C-13 of the SC-corrected (non-SC) organic matter range from -24.7 parts per thousand to -21.9 parts per thousand and -25.1 parts per thousand to -20.7 parts per thousand in the Jinju Formation, and -24.7 parts per thousand to -23.0 parts per thousand and from -26.4 parts per thousand to -21.7 parts per thousand in the Banyaweol Formation, respectively. Based on the delta C-13 values of coeval charcoal, the calculated delta C-13 of the original plant material in the surrounding watershed of the paleo-Jinju lake ranged from -21.8 parts per thousand to -17.8 parts per thousand (av. -19.3 parts per thousand). These values are considerably different from delta C-13 of vegetation (av.-24.3 parts per thousand) estimated from SC. The estimated delta C-13 values of non-SC organic carbon are different from those of the TOC, by up to 3.5 parts per thousand (either an enrichment or depletion across this value). This discrepancy indicates that the presence of SC in sedimentary organic carbon affected carbon isotope composition of TOC in the studied lacustrine deposits and led to increase uncertainty of interpretation of paleoenvironment of the watershed. For improving the paleoenvironmental reconstructions by utilizing the delta C-13 values of TOC in ancient lacustrine sediments, a correction for the contribution of SC to TOC needs to be considered. (C) 2012 Elsevier B.V. All rights reserved.

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