Late Pleistocene-Holocene vegetation and climate variability of the western Himalaya, India

Abstract

• Pollen, δ 13 C and TOC data revealed vegetation and climatic changes of western Himalaya during the last 15 ka. • Expansion of arboreals between 12.7 and 9.2 ka suggests a warm and humid environment . • A warm and humid climate from 7.8 to 5.2 ka represents the Holocene Climate Optima. • Vegetation expansion (decline) with enhanced (weaker) monsoon periods implies vegetation sensitivity to insolation driven ISM. Multiproxy analyses of sediment samples from a 2.7 m trench from western Himalaya have helped in the reconstruction of vegetation and climatic changes during the last ∼ 15.2 ka. The data revealed that between 15.2 and 12.7 ka, the region supported alpine–scrubs and trees interspersed with meadows in a cool and moderately humid climate. The lowest d 13 C values and coarse-grained sediment texture indicate improved hydroclimatic conditions. The expansion of arboreals between 12.7 and 9.2 ka also suggests a warm and humid climate. Despite this, slightly higher d 13 C values reflect decreasing hydrological conditions. Reduced arboreals and increased d 13 C values imply a cold and dry climate between ca. 9.2 and 7.8 ka. The proliferation of arboreals supports a warm and humid climate from 7.8 to 5.2 ka, representing the Holocene Climate Optima. However, between 5.2 and 3.7 ka, a decrease in arboreals with associated d 13 C values suggest climate deterioration. Based on changes in arboreals and non–arboreals, the Late Holocene phases advocate for warm and wet (ca. 3.7–2.3 ka), cool and dry (ca. 2.3–1.7 ka), and warm and wet (1.5–0.75 ka) climatic conditions, respectively. Since 0.75 ka, a modest increase in arboreals, TOC, and a decrease in d 13 C values, implying that hydroclimatic conditions have improved. These findings are broadly consistent with previous Himalayan palaeoclimatic reconstructions; nevertheless, the absence of any major shift in vegetation during the younger Dryas is surprising.