Vegetation history and palaeoclimate of the past 30Â kyr in Pakistan as inferred from the palynology of continental margin sediments off the Indus Delta

Palynological investigations on a continuous uppermost Pleistocene to Holocene high-resolution gravity core collected from the continental margin off the Indus Delta provide the first, uninterrupted, 30-kyr-long record of vegetation history and palaeoclimate of the Pakistan hinterland. Core analysis and interpretation allows the recognition of (1) greater glacial aridity than during the following postglacial period up to the present day; (2) a significant southward extension of the Himalayan sub-alpine and deciduous hardwood tree zone during the time interval from the Last Glacial Maximum (LGM) to the Younger Dryas cold interval; (3) extreme aridity and climatic deterioration during the LGM and the equivalent to Heinrich event 1; (4) a marked change to early Holocene humid conditions, starting already during the Bölling/Alleröd and increasing abruptly during the Preboreal period; and (5) a gradual reduction of humidity from the middle Holocene to the present. These results are in general agreement with palaeoclimatic reconstructions based on multiple proxies from the Indian subcontinent as well as the Arabian Sea, and especially confirm the occurrence of a clear precipitation maximum in Pakistan between ca. 9 and 7 cal. kyr BP which probably resulted from a combination of increased and prolonged summer (SW) monsoonal strength; both processes ultimately being controlled by orbital changes in northern hemisphere summer insolation and shifts in the position of the Intertropical Convergence Zone.