Speleothem evidence for changes in Indian summer monsoon precipitation over the last similar to 2300 years

Speleothems from a web-ventilated dolomitic cave in the Pokhara Valley, cen tral Nepal, preserve a mineralogic record of Indian summer monsoon variabil ity over the past 2300 yr, Annually deposited aragonite layers formed betwe en 2300 and 1500 yr B,P,, indicating reduced monsoon precipitation and incr eased cave aridity, whereas alternating calcite/aragonite laminae deposit e d after 1500 yr B,P. record elevated summer monsoon precipitation and incre ased cave humidity. Dense, optically clear calcite layers deposited from 45 0 +/- 5 to 360 +/- 20 yr B.P. (1550 to 1640 A.D,) indicate a less-evaporati ve cave environment and suggest moister and/or cooler conditions, possibly related to climatic change associated with the onset of the Little Ice Age. (C) 2000 University of Washington.