Geophysical Characteristics of Salinisation at Cape Portland, NE Tasmania
A. Howlett, M. J. Roach and J. E. Reid
ASEG Extended Abstracts
2001(1) 1 - 4
An integrated geophysical study of salinisation at Cape Portland, NE Tasmania, has mapped the distribution of saline areas, and has identified constrictions in the hydrogeologic basement and a possible source and transport mechanism for the salt. EM-31 data collected in the area not only clearly delineate the extent of salt scalds, but also highlight areas of elevated conductivity not visibly affected by salt. EM-31 data has enabled the distribution of the salt to be mapped at a much higher resolution than was previously possible using shallow drilling. Results from time-domain electromagnetic surveys confirm the responses seen in the EM-31 data and provide additional information about the subsurface distribution of saline material. Conductivity depth pseudosections and layered earth inversions indicate depressions of up to 140 m in the resistive basement are infilled with more conductive material. Ground magnetic data show the distribution of shallow Jurassic dolerite basement features and define a major negative amplitude anomaly which transects the study area. This feature is coincident with depressions identified from the time-domain electromagnetics and with a negative Bouguer gravity anomaly. The electromagnetic and potential field interpretations are consistent and indicate the presence of a major palaeochannel infilled with more conductive material. This feature is inferred to be the major control on salinisation in the study area.
Full text doi:10.1071/ASEG2001ab058
© ASEG 2001