PALEOCLIMATE INVESTIGATION OF LACUSTRINE SEDIMENT FROM LAKE TELMEN, MONGOLIA

Mongolia, located in Central Asia, experiences the most continental climate on Earth. Paleoclimate data collection from Mongolia is a relatively recent activity, largely confined to studies during the last two decades. Although detailed paleoclimate data are abundant for selected areas throughout Asia, datasets from within Mongolia are relatively scarce and display regional variability. Further regional data collection and multiproxy analysis can aid in resource management, as well as contribute to a greater understanding of past environmental change.

This study analyzes bulk carbonate isotopes and mineralogy on a 7,110 year long radiometrically-dated sediment core from Lake Telmen in north central Mongolia. Lake Telmen is presently a closed basin, saline (4 gL^-1) lake. Prior studies of this Lake Telmen sediment core used sedimentology, pollen, and diatoms to infer predominantly arid conditions between 7,110 and 4,390 yr BP and more humid conditions since. The fine fraction (<63 micron) carbonate stable isotope data were compared to existing Lake Telmen proxy data. Between 7,110 to 4,390 yr BP more positive δ¹⁸O shifts, averaging -0.46 ‰, correspond with aridity increases determined from pollen and diatom profiles. Preliminary X-ray diffraction shows the presence of ankerite in these arid intervals. Younger than 4,390 yr BP, a negative δ¹⁸O shift to values averaging -1.23 ‰ corresponds to generally more humid conditions inferred from the pollen and diatom profiles. Within the upper sediment, XRD analysis indicates the presence of authegenic monohydrocalcite formed by precipitation in the water column during productive summer months. Work is ongoing to further study XRD mineralogy and stable isotopes from ostracod valves.