HIGH-RESOLUTION RECORDS OF SOIL HUMIFICATION AND PALEOCLIMATE CHANGE FROM VARIATIONS IN SPELEOTHEM LUMINESCENCE EXCITATION AND EMISSION WAVELENGTHS

Recent advances in the precision and accuracy of the optical technique s required to measure luminescence permit the nondestructive analysis of solid geologic samples such as speleothems (secondary carbonate dep osits in caves). In this paper we show that measurement of speleothem luminescence demonstrates a strong relationship between the excitation and emission wavelengths and both the extent of soil humification and mean annual rainfall. Raw peat with blanket bog vegetation has the hi ghest humification and highest luminescence excitation and emission ma trix wavelengths, because of the higher proportion of high-molecular-w eight organic acids in these soils. Brown ranker and rendzina soils,vi th dry grassland and woodland cover have the lowest wavelengths. Detai led analysis of one site where an annually laminated stalagmite has be en deposited over the past 70 yr during a period with instrumental cli mate records and no vegetation change suggests that more subtle variat ions in luminescence emission wavelength correlate best with mean annu al rainfall, although there is a lag of similar to 10 yr. These result s are used to interpret soil humification and climate change from a 13 0 ka speleothem at an upland site in Yorkshire, England. These data pr ovide a new continuous terrestrial record of climate and environmental change for northwestern Europe and suggest the presence of significan t variations in wetness and vegetation within interglacial and interst adial periods.