HR: 0800h
AN: PP31A-1508    [Abstracts]
TI: Holocene Climatic Variability in the Cariboo Mountains, British Columbia, Based on Biogenic-silica Isotopes, Diatom Assemblages, Fire Frequency, and Vegetation Composition.
AU: Gavin, D G
EM: dgavin@uvm.edu
AF: University of Vermont, Botany and Agricultural Geochemistry, Burlington, VT 05405 United States
AU: * Henderson, A C
EM: ahenders@life.uiuc.edu
AF: University of Illinois, Plant Biology, Urbana, IL 61801 United States
AU: Hu, F
EM: fshu@life.uiuc.edu
AF: University of Illinois, Plant Biology, Urbana, IL 61801 United States
AU: Leng, M J
EM: mjl@nigl.nerc.ac.uk
AF: British Geological Survey, NERC Isotope Geosciences Laboratory, Keyworth, Nottingham, NG12 5GG United Kingdom
AU: Westover, K
EM: coyote@unlserve.unl.edu
AF: University of Nebraska, Department of Geology, Lincoln, NE 68588 United States
AB: The mountains of east-central British Columbia have a climate with both maritime and continental influences, with precipitation distributed equally over the year. The vegetation history of this region indicates the establishment of forests with species with a mainly coastal distribution (i.e., cedar-hemlock `rainforests') at c. 4000 years BP, suggesting the increased importance of maritime climatic elements. We investigated the climatic changes associated with the development of this forest type using multiple climate proxies from the Blue River region, using a 7 m, 11,000-yr sediment record from Eleanor Lake (56°7'N; 199°18'W; 860 m a.s.l.; max. depth 17 m). Chronological control is provided by 10 AMS radiocarbon dates, three tephra identifications, and ²¹⁰Pb. The lake remained deep throughout the Holocene, as evidenced by diatom assemblages (planktonic and tychoplanktonic low salinity species) and mineralogy (pyrite). A high-resolution biogenic silica record shows high lake productivity before c. 6000 years BP, coincident with frequent fire and pine-dominated forests, indicating warm/dry summers. These proxies also show several instances of abrupt climatic change during this period. The record of oxygen isotopes from biogenic-silica (δ¹⁸O_diat) (c. 75-year resolution) shows a millennial-scale trend with maximum values at 5000 years BP (c. 34‰ VSMOW), but there are also marked large-magnitude (c. 4‰) high frequency changes throughout the Holocene, including minimum values during a period coincident with the Little Ice Age. The trends in the δ¹⁸O_diat record suggest that oxygen-isotopes in this lake reflect changes in seasonality of both precipitation and temperature, as modern δ¹⁸O of lake water occur within the range of the local meteoric water line suggesting minimal evaporation. Our results show that sediment records from moist climatic regions, which lack carbonates, still may yield sensitive climatic reconstructions.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4942 Limnology (0458, 1845, 4239)
DE: 4950 Paleoecology
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005