T189 Limnogeology: Interdisciplinary Studies of Lakes and Paleolakes (Posters)

Tuesday, 11 October 2011
9:00 AM - 6:00 PM
Hall C

RECONSTRUCTION OF HOLOCENE PALEOCLIMATIC VARIABILITY USING HIGH RESOLUTION DIFFUSE SPECTRAL REFLECTANCE DATA FROM CLELAND LAKE, BRITISH COLUMBIA

Paper number: T189-39
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Visible derivative spectroscopy is applied to sediment from Cleland Lake, British Columbia to evaluate regional changes in Holocene paleoclimate. Principal component analysis (PCA) of the derivate-transformed diffuse spectral reflectance (DSR) data minimizes scattering effects on the spectra and extracts orthogonal components that can be related to sediment composition (Ortiz et al., 2009). Four major components explaining 95.94% of the variance were extracted from the lake sediment data. Components were identified by comparing the spectral signatures with that of known mineral and pigment standards. Component 1 correlates with the spectrum of cyanobacterial pigments (cyanophyta+phycocyanin) and can be used as a paleoproductivity proxy. Component 2 correlates with Dolomite+Kaolinite+Phycocyanin, while Component 3 and 4 had an inverse correlation with anhydrite+ muscovite+chlorophyllide-a, and sphalerite+Illite respectively. Down core variation of the component scores showed that periods of high productivity (higher levels of component 1) corresponds to higher levels of sphlerite+illite (component 3); possibly due to the development of anoxic bottom water conditions leading to authiginic sulfide deposition. Percent biogenic carbonate obtained by loss on ignition further shows that periods of low/high carbonate contents correspond to lower/higher lake productivity and dry/wet periods with limited/enhanced Ca+2 input to the lake.

Wavelet analysis performed on high resolution (up to decadal level) DSR data revealed two prominent periodicities in wet/dry proxies within the past 8,400 years. Multidecadal cyclicty in the 64-128 year band was prominent during the late Holocene (after ~ 2000 Calendar years B.P), possibly related to the low frequency part (~80 years) of the Pacific Decadal Oscillation. During the mid-Holocene (~2000 to 7000 years B.P) a significant variability of ~1,500 years was observed, corresponding to the Holocene millennial scale climatic oscillations. Cleland Lake’s response to changing climatic conditions in the Pacific Northwest is complex and need further study. Comparison of reflectance data with C and O isotope records from the lake basin sediments should help us to determine the processes driving this variability.