A HOLOCENE RECORD OF CLIMATE CHANGE IN THE EASTERN VOLGA BASIN: STABLE-ISOTOPE ANALYSIS OF A U-TH-DATED STALAGMITE FROM KINDERLINSKAYA CAVE, RUSSIA

The past and future impact of climate change on the Volga Basin is a current focus of intensive research by paleoclimatologists and climate modelers. While Holocene climatic shifts are well documented in coastal areas of western Eurasia, however, the past coupling of ocean dynamics and continental climate remains poorly understood, due to the lack of precisely dated, terrestrial climate records. Multi-proxy reconstructions of past hydrological conditions from precisely dated speleothems offer a powerful tool in exploring the impact of Holocene climate dynamics on moisture delivery to the continental interior. We report C- and O-isotope data at 0.5-mm resolution from a 35-cm stalagmite that was collected in growth position from Kinderlinskaya Cave, located in the western foothills of the southern Ural Mountains (56.1°N 55.8°E). The stalagmite, which is the first reported from Russia, grew between 11.8–1.8 ka, according to an age model constructed from 18 U-series dates. Cave monitoring to date confirms the suitability of our sample site (1.8 km from the cave entrance) for paleoclimate reconstruction. Microclimate of the “Brook Room” (RH = 100%; T = 6.2°C) does not vary seasonally, with the exception of a small (0.1°C) but measurable depression in temperature, which corresponds to melting of winter snowpack after a 1-month lag time. These data constrain the timing of speleothem growth and, along with δ¹⁸O analysis of cave drip water and local springs, suggest that stalagmite-δ¹⁸Ο variability is related to shifts in the δ¹⁸O of winter precipitation. Stalagmite δ¹⁸O increases along the growth axis from -14.5 to -11 (‰ V-PDB), broadly consistent with early to mid-Holocene warming trends. However, the difference in d¹⁸O between Kinderlinskaya Cave and Central European records is anomalously high during the early Holocene and decreases toward ~7 ka. On the other hand, millennial trends closely mimic those recently reported from Sofular Cave (Turkey) for the entire Holocene. Minimum δ¹³C values at Kinderlinskaya Cave also broadly coincide with humid intervals recorded in Sofular Cave during the Boreal and Atlantic stages. These correlations and discrepancies are explained through shifts in dominant atmospheric circulation modes related to ice-sheet dynamics, solar insolation, and land-sea temperature gradients.