ISOTOPIC AND PETROGRAPHIC EVIDENCE FOR QUATERNARY LONG-TERM CLIMATE CHANGE FROM A STALAGMITE FROM THE SERRA DO COUREL OF SPAIN

A stalagmite from Cova da Arcola in the Serra do Courel range in northwestern Spain serves as a record of both short-term and long-term climate shifts in the region. Twelve U-series dates ranging from approximately 235 ka to 1,000 years before present provide as generalized chronology for the stalagmite. Uncertainties are large, however it is clear that the stalagmite records two glacial and three interglacial periods. Short-term variations in environment may be deduced from fluctuations in stable isotope data, yielding relative dates of these fluctuations although exact timing may not be pinpointed due to the large margins of error in the U-series dates.

Stable isotope data from this stalagmite includes values of d¹³C ranging from -10.1 to -0.4‰ relative to VPDB and d¹⁶O values ranging from -7.2 to -5.3‰ relative to VPDB. The oxygen and carbon isotopes show weak correlation. A combination of stable isotope data and petrographic observations allows for the determination of paleoclimate from this stalagmite. Calcite predominates early in the stalagmite formation and values of d¹³C relative to VPDB are low, indicative of a warm and wet climate in the Holstein interglacial period. A transition to aragonite and a sharp increase in d¹³C values marks the transition to the Saalian glacial period. Deposition during the Eemian interglacial period continued to be predominately aragonite, however d¹³C values indicate a warmer climate. The Weichselian glacial is marked by very high values of d¹³C, up to -0.4‰, followed by abundant recrystallization and low d¹³C mark the Holocene interglacial at the top of the stalagmite.

Glacial and interglacial periods are clearly defined, and allow for an expansion of the climate trends observed in a smaller stalagmite from the same area that only records the past 9.3 ka. The paleoclimate record of this stalagmite is similar to records observed in the Greenland ice cores, though there is some variation in dates, suggesting the influence of Mediterranean climates especially during the Eemian interglaical period.