New Zealand and french scientists collaborate to investigate faults in sediments off Wanganui
French and New Zealand scientists are examining sediments deposited over the last two million years in the offshore Wanganui Basin.
The French scientists are from the Centre National de la Recherche Scientifique (CNRS) and the University of Rennes, and they are working with geologists and geophysicists from NIWA (the National Institute of Water and Atmospheric Research).
Their aim is to study the most recently active submarine faults in the basin and the influence of sea-level changes on the sequence in which the sediment was deposited.
"The results will be included in the NIWA offshore fault database, which will be used for earthquake coastal hazard assessment", said NIWA project leader Dr Geoffroy Lamarche.
"We get an understanding of what the environment was like when the sediments were deposited. We can recognise old beaches, estuaries, channels, and swamps, and so estimate sea-level fluctuations. This in turn helps us form a detailed history of the faults.
"However, because New Zealand is tectonically active, vertical movements of the earth's crust are also recorded in the sediment. One aim of the study is to distinguish changes which are related to movements of the tectonic plates and to sea-level changes. This helps us to understand the formation of deep sedimentary basins and the history of sea level recorded by sediments filling the basin."
The three-year project is funded by the Foundation for Research, Science and Technology. In November 1998, NIWA conducted a 25-day survey in offshore Taranaki and along the Wanganui and Kapiti coasts. The survey used NIWA's 70-metre research vessel Tangaroa, and it enabled scientists to acquire more than 2000 km of seismic reflection data and collect sediments samples. Seismic reflection data provide an image of the geology beneath the sea floor to a depth of about 2 kilometres.
In February 2000, financial support was granted by the French Ministry of Foreign Affairs to enable collaboration between two NIWA and two French scientists. Dr. Jean-Noel Proust, from CNRS in Rennes, and PhD student S�bastien Castelltort, from the University of Rennes, will work with geophysicist and project leader Dr Geoffroy Lamarche, and geologist Dr Scott Nodder, both from NIWA.
The fund covered visits by the French scientists to NIWA for three weeks in February, during which they went to Castlecliff Beach to observe the geology of the Wanganui Basin, which is exposed in a world-renowned coastal outcropping section. The New Zealand scientists will visit the Rennes Laboratories in April and June 2000. Sedimentologists from the Institute of Geological & Nuclear Sciences and Waikato University are also likely to be involved in the study.
"The results could be of interest to petroleum companies to evaluate the oil and gas potential off Wanganui", said Dr Lamarche.
