EAGER: Sedimentologyand Tephrochronology of Caves in the Melinau Karst, Sarawak, Malaysia

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Sedimentology and Tephrochronology of caves in the Melinau Karst, Sarawak, Malaysia.Donald A. McFarlane, Claremont McKenna CollegeEAR - 0952398ABSTRACT Gunung Mulu National Park, Sarawak, Malaysia, was established in 1974 to protect its world-class subterranean environment, and recognized for World Heritage status in 2000. Currently, this heritage incorporates some 295 kms of mapped cave, including some of the largest passages and chambers in the World. This proposal focuses on resolving the age and origin of a prominent volcanic ash layer preserved in the sediment deposits of several Mulu caves, on using that distinctive chrono-marker to understand the depositional history of the caves, and on isolating a concurrent geochemical signature in Mulu speleothems.PIs believe that the circumstantial evidence points to the ash layer being formed by the Younger Toba eruption - a cataclysmic event originating in northern Sumatra that is recognized as the most violent volcanic event in the past million years of Earth history. If the Mulu ash does prove to come from Toba, it will provide valuable new insights into the pattern of ash-fall and hence it's probable impact on ecosystems and human populations in southeast Asia. If the ash proves to originate elsewhere, then it must represent a hitherto unrecognized eruption of great significance. In either case, identifying a corresponding geochemical signature in a dated Mulu stalagmite may lay the groundwork for developing paleo-eruption records from speleothems Southeast Asia.