Lithologic mapping in the Oscar II coast area, Graham Land, Antarctic Peninsula using advanced spaceborne thermal emission and reflection radiometer (ASTER) data
|Category||GIS & Remote sensing|
|Location||International Geological Congress,oslo 2008|
|Author||Haselwimmer, Christian۱; Riley, Teal۱; Liu, Jian Guo۲|
|Holding Date||08 October 2008|
Multispectral and hyperspectral remote sensing has been used extensively around the world to assist geological mapping and resource exploration efforts. However, its use in Antarctica has been limited with no research yet undertaken on the mountainous Antarctic Peninsula.
The results of the first attempt to use ASTER data for the purposes of lithologic mapping on the peninsula are presented for an area on the Oscar II Coast, Eastern Graham Land. The geology of the study area comprises predominantly of silicic volcanic rocks and associated deposits (Mapple Formation), which overly minor exposures of terrestrial and marine sediments (Botany Bay and Trinity Peninsula groups) that are together intruded by plutons of acidic to intermediate composition. Lab spectroscopy of samples from the study area indicates that beyond minor FeO enrichment weathering has little effect on rock spectral reflectance. Igneous rocks display mixed Al-OH and Mg-OH absorption features related to the presence of authigenic kaolinite, illite, smectite, muscovite, chlorite and epidote that are interpreted as the products of low-grade alteration of primary feldspars and mafic minerals. Stronger Al-OH and Mg-OH absorption features seen within the volcanic rocks reflect more intense hydrothermal alteration to argillic and propylitic grades. Spectra from Botany Bay and Trinity Peninsula Group sediments display limited diagnostic features.
Image processing of two ASTER scenes covering the areas around Cape Disappointment and Exasperation Inlet was applied using the Level 1B VNIR/SWIR bands and the standard TIR emissivity product (AST05). Calibration of VNIR/SWIR data utilised the FLAASH correction procedure followed by scalar adjustment using lab spectra of samples from a homogeneous granodiorite exposure. Analysis of sunlit rock outcrops within the VNIR/SWIR and TIR datasets utilised band ratios and the matched-filtering (MF) procedure run using image-derived end-members and ASTER-convolved rock spectra. In the VNIR/SWIR region the use of image end-members produced the best results enabling the discrimination of six major mineral classes that were in good agreement with the outcomes of lab spectroscopy. Analysis of TIR emissivity data enabled the discrimination of three major spectral classes with varying strength SiO emission features indicative of rocks of strongly felsic to intermediate compositions. The results have enabled the direct mapping of granitoid and diorite intrusions as well as extending the coverage of the Mapple Formation into un-mapped areas in the northwest of the study area. Identification of specific minerals has highlighted areas of strong hydrothermal alteration within the Mapple Formation volcanics and suggested that subtle compositional sub-units may also be present. This case study has shown that whilst the effects of limited rock exposure and mountain shadowing are severe, useful lithologic information may still be retrieved using multispectral data.