Palaeoclimatic implications of the growth history and stable isotope (y18O and y13C) geochemistry of a Middle to Late Pleistocene stalagmite from central-western Italy

Abstract

The age structure and stable isotope composition of a stalagmite (CC1) from an upland cave in central-western Italy were studied to investigate regional response to global climatic changes. Four growth phases are constrained by 28 thermal ionization and multi-collector inductively coupled plasma mass spectrometry Th–U ages and reveal intermittent deposition through the period between Marine Isotope Stage (MIS) 11 and 3 (~380 and ~43 kyr). Most of the growth took place between ~380 and ~280 kyr, a period punctuated briefly by a hiatus in deposition through the glacial maximum of MIS 10. Growth was terminated abruptly at 280 kyr just prior to the MIS 8 glacial maximum.With a present-day chamber temperature of 7.5 8C, the timing of hiatuses close to these glacial maxima point to freezing conditions at the time. No deposition was recorded through the entirety of MIS 7 and most of MIS 6, whilst two minor growth phases occurred at ~141–125 and ~43 kyr. Growth at 141 kyr indicates temperatures N0 8C at a time when MIS 6 ice volumes were close to their maximum. High stable carbon isotope (y13C) values ( 2.8x to +3.1x) throughout the stalagmite’s growth reflect a persistently low input of biogenic CO2, indicating that the steep, barren and alpine-like recharge area of today has been in existence for at least the last ~380 kyr. During MIS 9, the lowest y13C values occur well after maximum interglacial conditions, suggesting a lag in the development of post-glacial soils in this high-altitude karst. The stable oxygen isotope (y18O) trends match the main structural features of the major climate proxy records (SPECMAP, Vostok and Devils Hole), suggesting that the y18O of CC1 has responded to global-scale climate changes, whilst remarkable similarity exists between CC1 y18O and regional sea-surface temperature reconstructions from North Atlantic core ODP980 and southwest Pacific marine core MD97-2120 through the most detailed part of the CC1 record, MIS 9–8. The results suggest that CC1 and other stalagmites from the cave have the potential to capture a long record of regional temperature trends, particularly in regards to the relative severity of Pleistocene glacial stages. D 2004 Elsevier B.V. All rights reserved.