2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 14
Presentation Time: 8:00 AM-12:00 PM


POLK, Jason Samuel, Dept. of Environmental Science and Policy, University of South Florida, 4202 E. Fowler Ave, NES 319, Tampa, FL 33620, VAN BEYNEN, Philip, Dept. of Environmental Science and Policy, Univ of South Florida, 4202 E. Fowler Ave, NES 313, Tampa, FL 33620 and REEDER, Philip, Department of Geography, Univ of South Florida, 4202 East Fowler Ave, Tampa, FL 33620, jspolk@mail.usf.edu

Cave sediments (RC/SC04-01) from Reflection Cave on the Vaca Plateau, Belize were analyzed to infer regional changes in vegetation based on variations in the δ13C in the sediment record. The sediment layers were 14C dated to provide a temporal scale of deposition and the stable isotopes 12C/13C were analyzed using mass spectrometry to determine changes in vegetation from forested (C3) to arid grass (C4) conditions. Several shifts in vegetation, including a dramatic change ~ 2,200 years ago, were found in the isotopic record. A close correlation exists between the cave sediment record, the δ13C signal from a speleothem in the same study area, and two nearby lacustrine cores from Lake Chichancanab, Yucatan Peninsula. Similarities between the records suggest regional vegetation shifts over the last 2,800 years. The cause for these regional changes in vegetation is changing precipitation levels due to the position of the Bermuda High and the Intertropical Convergence Zone (ITCZ), affecting the strength of the Easterly Trade winds.