PARENT SESSION
Symposium #26: Gasping for CO2: Ecological Effects of Past Variations in Atmospheric CO2.
Organized by: JW Williams and S Cowling
Thursday, August 8. 9:00 AM to 11:30 AM. Turquoise Ballroom, TCC.
Climate and vegetation change inferred from hydrogen and carbon isotope variations of land-plant biomarkers from Lake Tulane sediment during the last glacial-interglacial cycle.
Huang, Yongsong*,1, Shuman, Bryan1, Wang, Yi1, Jacobson, George2, Grimm, Eric3, Webb, Thompson1, 1 Department of Geological Sciences, Providence, RI 029122 Institute for Quaternary and Climate Studies, Orono, ME 044693 3Illinois State Museum, Springfield, IL 62703
ABSTRACT- We determined the variations in hydrogen and carbon isotope ratioss for individual terrestrial plant biomarkers in a sediment core from Lake Tulane, Florida using gas chromatography-isotope ratio mass spectrometry. The sediment core spans the last 70,000 years, and is the longest continuous lake-sediment record from eastern North America. The resolution of our preliminary analysis is 1 to 2 samples (depending on compounds) per 1000 years. High-resolution pollen and other stratigraphic data allow an assessment of the climate history; a chronology was established using more than 40 AMS dates on newly collected cores. Enhanced (40 to 70 per mil) hydrogen isotope values of terrestrial biomarkers indicate a generally drier conditions during the last glacial period, consistent with higher abundance of ragweed shown in the pollen data. Carbon isotope ratios also indicate a significantly enhanced C4 plant abundance during the last glacial than the Holocene. The higher abundance of C4 plants is interpreted as a result of combined drier conditions as well as lower atmospheric CO2 levels.
KEY WORDS: isotope, leaf wax, lake sediments