HYDROLOGIC CONTROL ON THE OXYGEN-ISOTOPE RELATION BETWEEN SEDIMENT CELLULOSE AND LAKE WATER, WESTERN TAIMYR PENINSULA, RUSSIA - IMPLICATIONS FOR THE USE OF SURFACE-SEDIMENT CALIBRATIONS IN PALEOLIMNOLOGY

Systematic variability occurs between the oxygen isotopic composition of lake water sampled in mid-summer 1993 and cellulose extracted from surficial sediments of a suite of lakes spanning the forest-tundra tra nsition near Noril'sk, Russia. Some tundra and all forest-tundra lakes show greater deviation from expected cellulose-water isotopic separat ion than forest lakes, apparently because of greater sensitivity to O- 18-depleted snowmelt contributions. Cellulose derived from aquatic pla nts naturally integrates fluctuations in lake water delta(18)O, provid ing a signal that is inherently more representative of average thaw se ason lake water delta(18)O than the measure of instantaneous delta(18) O obtained from an individual sample of lake water. Thus, indiscrimina te use of empirical cellulose-water relations derived from 'calibratio n' samples could lead to erroneous assessment of paleohydrology from t he oxygen-isotope stratigraphy of sediment cores from arctic lakes. Ho wever, deviation from the expected cellulose-water fractionation is a source of lake-specific hydrologic information useful for qualifying p aleoenvironmental interpretations and possibly constraining non-isotop ic methods that rely on surface-sediment calibrations.