TROPICAL CYLONE ORIGIN OF MUD LAYERS IN STALAGMITES FROM TROPICAL AUSTRALIA

Our ability to understand multi-decadal to centennial-scale trends in tropical cyclone activity is limited by the short duration of, and limitations in, historical records. In order to extend these records for tropical Western Australia, we have analyzed mud layers in stalagmite KNI-51-11 from the Kimberley region of north-central Australia. KNI-51-11 is an aragonite stalagmite that grew over the last 250 years (with one multi-decadal hiatus) and contains 39 mud layers. High uranium (~5 ppm) and low detrital Th abundances in this stalagmite allow extremely precise dating (±1 year over the past century) via U/Th MC-ICP-MS methods. Linear interpolation between 13 U/Th dates was used to establish an age model and an online tropical cyclone tracking protocol developed and maintained by the Australian Bureau of Meteorology provides intensities and tracks of tropical cyclone over the past century. Comparison of mud layer ages with historical tropical cyclone activity reveals that the majority (~75%) of KNI-51-11 mud layers appear to have formed during or within dating error of years in which tropical cyclones passed within 200 km of KNI-51. Thus, it appears that the intense rainfall events associated with tropical cyclones mobilizes fine grained sediment within cave KNI-51 flood waters, coating stalagmite caps, and these sediments are later covered over by subsequent stalagmite growth. This technique may thus offer a readily extractable, high resolution record of tropical cyclone landfalls that could be extended across the late Holocene.