Chronology and paleoenvironment of Marine Isotope Stage 3 from two high-elevation speleothems, Austrian Alps

A new high-resolution stable isotope record from the alpine Kleegruben Cave (2165 m, Central Alps) is presented. This record largely duplicates a previously reported speleothem record from this site. High-precision U-series thermal ionization mass spectrometry dates constrain the growth history of this new sample (56-48 ka) to the Marine Isotope Stage (MIS) 3. Both stalagmites reveal highly similar variations in O isotopes that can be directly compared to O isotope variability associated with Dansgaard-Oeschger interstadials recorded in the Greenland ice cores (Greenland Interstadials, GIS). Based on the new record we refine our previous age assignments of the GIS during this time interval, i.e. GIS 15b at 55.7 ka, GIS 15a at 55.3 ka, onset (mid-point) of the prominent GIS 14 at 54.5 yr and onset of GIS 12 at approx. 48 ka. The overall uncertainties associated with these ages are 0.1-0.3 ka. The timing of these Dansgaard-Oeschger interstadials is within 0.2 ka of the newly proposed GRIP.SFCP04 timescale. The age data for both Kleegruben stalagmites demonstrate that liquid water was at least seasonally present in the shallow sub-surface allowing calcite precipitation to continue even during stadials of MIS 3. Given the present-day low temperature (+2.4 degC), we propose that these unusual speleothems formed in a karst system overlain by a warm-based glacier.