Late Quaternary climate history of the Horton Plains, central Sri Lanka.

Abstract A 6 m long core was retrieved from a mire at ca 2200 m a.s.l. in the Horton Plains National Park, central Sri Lanka. The material collected consists of a mixture of organic matter and clastic particles, which have been subject to bio-, litho- and chronostratigraphic analyses. The pollen spectra suggest semi-arid conditions and a relatively species-poor plant community from >24,000 until 18,500 cal yr BP associated with a weaker South West Monsoon (SWM). During the late Pleistocene, the climate was fluctuating between relatively dry and humid conditions as the result of changes in the monsoonal regime. The onset of the moonson caused a semi-humid climate resulting in an expansion of the Upper Montane Rain Forest (UMRF). The strengthening of the SWM was interrupted by two relatively dry climatic events, each lasting ca 2000 years. The early Holocene was characterised by a per-humid event followed by a hyper-humid event, both influenced by a further strengthening of the SWM due to the orbitally induced maximum increment of summer insolation. The middle Holocene was marked by a trend towards semi-arid climatic conditions. During the late Holocene, the SWM rains strengthened again.