Storm chasing in the Australian Tropics: Is there a record of past tropical cyclones in Lake Eacham?

The occurrence of extreme events, such as tropical cyclones, can cause large amounts of landscape and ecosystem disturbance and leave a sedimentary or erosional ‘signature’ in the landscape. The knowledge of past disturbance events can be incredibly beneficial in deciphering the future responses of these events in a time of climate variability. While there has been considerable focus on the reconstruction of tropical cyclone activity with the use of coastal sedimentary sequences, little attention has been directed in assessing the suitability of paleo lakes as recorders of tropical cyclone occurrences. Maar lakes are considered to be ideal for paleoenvironmental investigations as the sediment sequences collected in their basin can be likened to continuous archives of the environmental history of the lake and its surrounds. This study proposes that Lake Eacham (17°17’S, 145°37’E, 746m.a.s.l.), a maar lake located on the Atherton Tablelands in Northeast Queensland, contains a ‘signature’ of tropical cyclones in its sedimentary record and is a likely candidate for future investigations to construct a record of past-tropical cyclone events for the region. To identify a tropical cyclone ‘signature’, Itrax XRF, grainsize and Loss-On-Ignition analyses data was used produce a facies classification for the 40cm sediment sequence collected from the lake. The analysis of the impact of past tropical cyclones from historical climate data was also undertaken to identify events that had impacted Lake Eacham. A sediment-influx signal characterised by increased grainsize, peaks of detrital elements (Fe, Si, Rb, Ti) and reductions in organic content was evident in facies units which were associated with tropical cyclone activity. However, the relationship between the response of the catchment and tropical cyclones is significantly more complex than first assumed. Considering this, there is indeed an observable tropical cyclone ‘signature’ within the stratigraphy of Lake Eacham, however further investigations will allow for greater understanding into the non-homogenous response of the catchment to such events.