An investigation of the geological and geomorphological features of Fowlers Gap using thermal infrared, radar and airborne geophysical remote sensing techniques.

Abstract

This study summarises the application of several remote sensing techniques to investigate various components of a land surface in the semi-arid environment of Fowlers Gap. These remote sensing techniques included NASA's Thermal Infrared Multispectral Scanner (TIMS) and CSIRO's Mid-Infrared Airborne CO, Laser Spectrometer (MIRACO,LAS), NASA's AIRSAR radar and geophysical airborne radiometrics. Linear spectral unmixing of extracted emissivities from the TIMS data produced four endmembers: quartz, clay minerals, dry vegetation (cellulose) in fine soils, and green vegetation/moisture. MIRAC0,LAS data identified spectral signatures similar to the spectra of endmembers derived from TIMS data. The sensitivity of both thermal infrared remote sensing techniques to the quartzklay contents and textures of the soils and sediments was confirmed by detailed laboratory spectral measurements. Surface roughness information from AIRSAR's band C radar backscatter assisted the discrimination of alluvial and colluvial quartz and clay-rich deposits from the outcropping geological units. In particular the C band AIRSAR radar discriminated the coarse grained sandstone and quartzite scree within the colluvial pediments, from the finer grained quartz-rich 'radar smooth' alluvium in the scalds. Airborne radiometrics were also found useful for further discriminating potassium and thorium- bearing phyllosilicate/clay minerals, within shales and ghyllites, from the kaolinite and montmorillonite- rich alluvium. This study found that TIMS data could identify some of the geomorphological features at Fowlers Gap, such as colluvial pediments, depositional scalds and gilgai landforms, that characterise some of the land systems in the Lowlands and Plains relief class of the Fowlers Gap land system classification. Thermal infrared remote sensing techniques also proved capable of discriminating areas of cellulose-rich dry vegetation and fine grained soils within the Plains relief class. The sensitivity of AIRSAR radar for topographic relief and surface roughness suggests that it is useful for distinguishing land systems in the Ranges relief class. Radiometrics appeared useful for land system definition when outcropping argillaceous units and alluvium assisted their classification. Key words: remote sensing, Fowlers Gap, thermal infrared, land system, spectral unmixing