Abstract:
This study investigates gravity cores and multibeam bathymetry data carried out off the western coast of Fiordland, in order to determine the processes of transport and the dispersal pathways of sediment in offshore Fiordland, with the ultimate goal of finding out if turbidity current deposits are a useful palaeoseismic record. Laboratory methods including core logging, x-radiograph analysis and laser grain size analysis were carried out to determine the mode of emplacement of the layers within the cores, and carbonate, x-ray diffraction, multibeam bathymetry and backscatter analysis were used in order to determine the submarine dispersal pathways of sediment in offshore Fiordland. This study discovered that turbidites within Looking Glass Basin, Secretary-Nancy Basin and around Bligh Ridge consist of stacked turbidites, which display traction carpet behaviour and in many cases contain multiple coarse grain pulses, suggesting that seismic activity is the likely trigger for the turbidity currents. The multibeam bathymetry and backscatter data showed that the source for the sediment within these turbidites was the continental slope, and that the flows were channelised until they a fan or basin, in which they are deposited. Radiocarbon dating was found to correlate with the on shore record, but care must be taken with the data since the samples were taken from the tail of the turbidite, therefore likely to have dated the sediments initial emplacement before re-mobilisation, rather than the age of the turbidite itself.
