5:15 PM - 7:15 PM
[HQR05-P10] Total organic carbon contents and charcoal concentrations in Lake Biwa sediments: Implications for their marked increases in the terminal Pleistocene
Keywords:TOC content, microcharcoal, Lake Biwa
Total organic carbon (TOC) contents in lake sediments serve an indicator of biological production in the lake and the inflows of organic materials from the surrounding land. Previous studies have shown that in the Lake Biwa sediments, TOC contents markedly increased around 13 ka. The increase has been interpreted as being caused by nearby flooding. In contrast, some studies have suggested that the increase may be related to microcharcoals or the fires that produced them, as implied by the abundance of microcharcoals around the same time. However, the relationship between high TOC contents and abundant microcharcoals has rarely been studied. In this study, we examined both TOC contents and microcharcoal concentrations in Lake Biwa sediments over the past 20 kyrs to clarify their relationship. This study used the BIW07-2 and BIW07-5 cores, for which the detailed descriptions are provided in Takemura et al. (2010).
High TOC contents and high microcharcoal concentrations were observed between 13-9.5 ka. In addition, the peaks in TOC contents and microcharcoal concentrations coincided at 12.7 ka. We estimated the carbon content of the microcharcoals in the sediments, which led to the conclusion that the increase in microcharcoals was unlikely to have directly contributed to the increase in TOC contents. This study, along with previous research, suggest that the increases in TOC contents and microcharcoal concentrations were due to the inflow of herbaceous plant materials. These findings imply that the increase in TOC contents during the terminal Pleistocene resulted from the inflow of organic matter from herbaceous plant materials and soils, driven by the expansion and maintenance of grasslands and bare land related to the fire occurrences during that period.
Acknowledgment: The core samples used in this study were drilled using the Grant-in-Aid for Scientific Research (A) from Japan Society for the Promotion of Science ｢High resolution multiple time scale analysis of Lake Biwa sediments -Research on climate and tectonics during past 150,000 years｣ (No. 19204050 to K. Takemura).
Reference: Takemura et al. (2010) The Quaternary Research, 49(3), 147-160.
High TOC contents and high microcharcoal concentrations were observed between 13-9.5 ka. In addition, the peaks in TOC contents and microcharcoal concentrations coincided at 12.7 ka. We estimated the carbon content of the microcharcoals in the sediments, which led to the conclusion that the increase in microcharcoals was unlikely to have directly contributed to the increase in TOC contents. This study, along with previous research, suggest that the increases in TOC contents and microcharcoal concentrations were due to the inflow of herbaceous plant materials. These findings imply that the increase in TOC contents during the terminal Pleistocene resulted from the inflow of organic matter from herbaceous plant materials and soils, driven by the expansion and maintenance of grasslands and bare land related to the fire occurrences during that period.
Acknowledgment: The core samples used in this study were drilled using the Grant-in-Aid for Scientific Research (A) from Japan Society for the Promotion of Science ｢High resolution multiple time scale analysis of Lake Biwa sediments -Research on climate and tectonics during past 150,000 years｣ (No. 19204050 to K. Takemura).
Reference: Takemura et al. (2010) The Quaternary Research, 49(3), 147-160.