Late Pleistocene pollen assemblages from the Thimi Formation, Kathmandu Valley, Nepal



Abstract  The Thimi Formation, constituting the upper part of the sedimentary sequence of the Kathmandu Valley, is characterized by alternation of fine- to medium-grained sand, silt, silty clay and clay deposited by a distal fluvial system in the Late Pleistocene. Palynostratigraphy based on 40 samples revealed the dominance of gymnosperm taxa over angiosperms and herbaceous members. As the different species Pinus and Quercus grow at different altitudes in Nepal today, an attempt was made to identify these taxa up to species level for climate interpretations. Gymnosperms, such as Pinus wallichiana, Pinus roxburghii, Abies spectabilis, Tsuga dumosa and Picea smithiana, were dominant over the woody angiosperms, such as Quercus lanata, Quercus lamellosa, Quercus leucotrichophora, Quercus semecarpifolia, Betula, Juglans, Myrica, Castanopsis and Symplocos. The pollen diagram of the Thimi Formation shows only minor fluctuations in assemblage. The pollen assemblages indicate the prevalence of a cool and temperate climate during the late Pleistocene. This is confirmed by the high percentages of Poaceae and other herbaceous plants, with very few woody angiosperms.