2002 ARCSS All-Hands Workshop

Investigation into the relationship between Climate Change and Sedimentary Processes from Core PG 1351 from El’gygytgyn Crater Lake, NE Siberia

Celeste A. Asikainen¹, Julie Brigham-Grette², Pierre Francus³, Michael Apfelbaum^4
1Departmen of Geosciences, University of Massachusetts, 233 Morrill Science Center, Amherst, MA, 01003, USA, Phone 413-545-2286, Fax 413-545-1200, celeste@geo.umass.edu
²Department of Geosciences, University of Massachusetts, 233 Morrill Science Center, Amherst, MA, 01003, USA, Phone 413-545-4840, Fax 413-545-1200, Juliebg@geo.umass.edu
³Department of Geosciences, University of Massachusetts, 233 Morrill Scinece Center, 611 North Pleasant Street, Amherst, MA, 01003-9297, USA, Phone 413-545-0659, Fax 413-545-1200, francus@geo.umass.edu
⁴Departmen of Geosciences, University of Massachusetts, 233 Morrill Science Center, Amherst, MA, 01003, USA, Phone 413-545-2286, Fax 413- 545-1200, michaela@geo.umass.edu

Sedimentological analyses completed at UMass so far from the upper 650 cm of the 1998 pilot core shows that Lake El’gygytgyn records large climate shifts for the last ~140 ka. The established chronology is based on magnetic susceptibility and OSL correlated to the GISP2 ¹⁸O curve (Nowaczyk, et al., in press, Geophys Res. Intern). Magnetic susceptibility varies by nearly two orders of magnitude and reflects the climatic and environmental history of northeastern Siberia over several glacial/interglacial cycles. High susceptibility in the sediments correlates with warm conditions (interglacial-like) with more oxygenated bottom waters. Low susceptibility correlates to cold (glacial) periods when perennial ice-cover causes anoxia and the dissolution of magnetic carrier materials. Oxygen deficient conditions preserved laminated sequences of the core. A bioturbation index (c.f., Behl and Kennet, 1996) correlates well to the susceptibility and TOC (Melles, in prep) curves.

The clay mineral assemblages in the sediment are illite, highly inter-stratified illite-smectite (I-S) and chlorite. Clay mineralogy is sensitive to changes in climate and can be used as a proxy for paleoclimate reconstruction. Under warm hydrolyzing conditions chlorite weathers more easily and I-S abundance increases, producing an inverse relationship in the relative abundance of these clays (Chamley, 1989). Trends in relative abundance show distinct downcore changes that correlate with susceptibility and other proxies. These trends can be divided into eight climate-related zones beginning with isotopic stage 3. Fluctuations in zones 6 - 4 suggest a change in climate that may be correlative with the transition from the Bølling-Allerød (13-11 ka) into the Younger Dryas (11-10 ka).

Grain-size downcore indicate that changes in magnetic susceptibility are not a function of grain size. The mean grain-size is in the silt fraction, with few grains larger then 60 µm. Terrigenous input to the lake comes from over 50 streams that are filtered through storm berms, limiting clastic deposition into the lake system.

Bleb structures, from the laminated segments of the core, were analyzed in thin-section using SEM (scanning electron microscope) in BSE (backscatter mode). The bleb texture, and structure, suggests different modes of deposition different from the surrounding laminae.

Using the BSE imaging technique we aim to quantify the detrital input and redox conditions that control diatom abundance, vivianite and diagenesis (c.f., Francus, 2001, 2000, 1998). Thus improving our understanding of the climate controlled sedimentary processes operating in this lake system.

Reference List:

Chamley, H., 1989. Clay Sedimentology. Springer, Berlin. Heidelberg New York, p.425

Francus P., 2001. Quantification of bioturbation in hemipelagic sediments via thin-sections image analysis. Journal of Sedimentary Research, 71, 3, 501-507.

Francus P. and Karabanov E., 2000. A computer-assisted thin-section study of lake Baikal sediments: a tool for understanding sedimentary processes and deciphering their climatic signal. International Journal of Earth Sciences, Geologische Rundschau, 89, 2, 260-267.

Francus P., 1998. An image analysis technique to measure grain-size variation in thin sections of soft clastic sediments. Sedimentary Geology, 121: 289-298.

Behl and Kennet (1996) Brief interstadial events in the Santa Barbara basin, NE Pacific, during the past 60 kyr, Nature, 379, 243-246.

Nowaczyk, N.R., Minyuk, P., Melles, M., Brigham-Grette, J., Glushkova, O., Nolan, M., Lozhkin, A.V., Stetsenko, T.V., Andersen, P., and Forman, S.L., 2002. Magnetostratigraphic results from impact crater Lake El’gygytgyn, North-eastern Siberia: a 300 kyr long high-resolution terrestrial paleoclimate record from the Arctic. Geophysical Journal International, in press.

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