1,350,000 Year History of Siberian Permafrost Based on U-Pb Chronology of Speleothems

Monday, 15 December 2014
Anton Vaks1, Andrew J. Mason2, Sebastian F. M. Breitenbach3, Alexander M. Kononov4, Alexander V. Osintcev5 and Gideon Mark Henderson2, (1)University of Oxford, Earth Sciences, Oxford, 0X1, United Kingdom, (2)University of Oxford, Earth Sciences, Oxford, United Kingdom, (3)ETH Swiss Federal Institute of Technology Zurich, Climate Geology, Zurich, Switzerland, (4)Institute of Earth’s Crust, Russian Academy of Science, Siberian Branch, Irkutsk, Russia, (5)Arabica Speleological Club, Irkutsk, Russia
Permafrost history of the last ~1.35 millions of years (Ma) was reconstructed using chronology of speleothems from a Siberian cave. Rain and snowmelt waters can penetrate into caves only when soil and subsoil temperatures are above 0°C and permafrost above the cave is discontinuous or absent. Speleothems in regions currently affected by permafrost therefore provide a tracer of past permafrost thawing events.

Ledyanaya Lenskaya Cave is located at 60°22’N-116°57’E, on the southern boundary of modern continuous permafrost, with no present-day water seepage and a mean annual temperature of -5°C ‒ -6°C. U-Th dating of speleothems from this cave in a previous study [1] showed that the youngest speleothem growth period occurred at 427±23 thousand years ago (ka), during early Marine Isotope Stage (MIS) 11. In this study we dated several horizons of older speleothems from this cave using the U-Pb method [2]. Two high precision ages indicate growth at 1074.2 +6.6/-5.2 ka and 947.8 +3.3/-3.4 ka, while new preliminary data provide strong evidence of an older growth period around 1.35-1.30 Ma. Other preliminary data mostly overlap the high precision ages, but also hint at limited growth at ~860 ka, with one data point suggesting younger, but minor growth at ~560 ka. The timing of these permafrost thawing events apparently correlates with interglacial episodes of exceptionally high Pacific Warm Pool sea surface temperature (~30°C) [3]. During these warm episodes the average global temperature was 1.1-1.5°C higher than pre-industrial temperatures. These findings put the threshold of thawing of continuous permafrost at its southern boundary at slightly more than 1.0°C above preindustrial level.


1. Vaks, A., et al., Science, 2013. 340 (6129): p. 183-186.

2. Mason, A.J., G.M. Henderson, and A. Vaks, Geostandards and Geoanalytical Research, 2013. 37(3): p. 261-275.

3. Hansen, J., et al., Proceedings of the National Academy of Sciences, 2006. 103(39): p. 14288-14293.