International Geologiical Congress - Oslo 2008

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GTR-02 Geological mapping using satellite techniques

 

Integrating remote sensing and geological fieldwork in the Kufra Basin, Southeast Libya

 

Alexander Schimanski, StatoilHydro ASA (Norway)
Matthias Tischler, StatoilHydro ASA (Norway)
Tore Indreiten, StatoilHydro ASA (Norway)
Simon Higgins, StatoilHydro ASA (Norway)
Hans Morten Bjornseth, StatoilHydro ASA (Norway)
Heike R. Groeger, StatoilHydro ASA (Norway)
 

 

Geological examination of the Kufra Basin, Southeast Libya, demonstrates how the integration of remote sensing and geological field work can improve the understanding of regional structures, stratigraphy and basin development. This case study focuses on Palaeozoic rocks exposed at the northern (Jebel Dalma) and eastern (Jebel Asba) rim of the Kufra Basin and aims to document the uses and limitations of remote sensing in onshore basin analysis.

GIS tools facilitate the integration of diverse datasets during interpretation in the office as well as in the field. Satellite imagery provides valuable information for geological interpretation of outcrops, particularly in desert areas like Southern Libya. In this case study we have used Landsat, ASTER, SPOT and Quickbird imagery as well as ASTER digital elevation data to interpret lineaments and bedding. In areas of shallowly inclined bedding (dips <15°) the reconstruction of dip directions from satellite images and digital elevation models can prove more reliable than field measurements in identifying regional trends. We furthermore used multispectral imagery from the ASTER sensor to discriminate lithologies and to facilitate geological mapping. In addition to band combinations optimized for geological interpretation, series of different band ratios are tested for their suitability for mapping. To address the challenges of differentiating between highly similar geological units, supervised classification of key lithologies has been carried out. Methodologies for the calculation of bedding attitude, fault interpretation and the identification of rock types from satellite images are groundtruthed in the field.

Local variations of the regional scale deformation within the Kufra Basin, such as the low angle dip of the Palaeozoic rocks towards the basin centre, can be readily identified on satellite images. Lineaments with clear offsets can be used to formulate a preliminary structural interpretation that allows for identification of key outcrops for further field work. Field observations are crucial to test the geological hypotheses developed using satellite imagery, and in turn allow for a better understanding of the remote sensing data. The integration of different scales (regional scale on satellite images, outcrop scale in the field) improves the quality of the final interpretation.

 

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