Stalagmite Based High Resolution ?18O Record of Indian Summer Monsoon Activity in Lesser Himalaya during the late Holocene

摘要

The oxygen isotopic (δ18O) records from speleothems, particularly stalagmites, provide very valuable information to reconstruct paleomonsoon history. Here we present a high-resolution record of Indian summer monsoon (ISM) precipitation for the 2,851 and 677 year BP using a U-Th dated stalagmite sample from lesser Himalayan cave. The stalagmite (BGR1) may have been developed under the isotopic equilibrium condition as revealed by its almost identical δ18O values of selected growth layers (Hendy test). X-ray diffraction analysis of BGR1 stalagmite shows predominance of calcite mineral. The δ18O values exhibit significant changes (ranging from -6.92 to -10.24‰ vs. VPDB) during the studied time interval. Based on our δ18O record, the climatic activity in lesser Himalaya can be categorized in two distinct phases, (a) a relatively dry period from 2,851 to 1,031 year BP and (b) a moderately wet period between 1,031 and 677 year BP. The spectral analysis of δ18O time series reveals a range of significant periodic components reflecting the control of solar activity on ISM variability.