Abstract/Summary

Establishing the chronology of humid and arid phases in southern Libya requires identification and sampling of appropriate sedimentary deposits. Lacustrine deposits tend to contain particularly useful palaeoenvironmental records. The current hyperaridity of the region leads to rapid aeolian erosion of lacustrine sediments and, thus, very spatially limited target sites. However, lacustrine deposits are often capped by a layer of duricrust; cementation is highly variable, but usually involves one of, or a combination of, calcium carbonate, silica, or gypsum. Both carbonate and gypsum can be readily identified by optical remote sensing systems operating in the visible to shortwave infrared part of the electromagnetic spectrum, such as the Landsat Thematic Mapper and the MODIS instrument carried on board EOS AQUA and TERRA missions. However, these systems are not able to discriminate a duricrust composed mostly of silica, due to its chemical similarity with the quartz sand background material within which these duricrust outcrops occur. Therefore, a robust remote sensing sampling system of potential palaeoenvironmental records in Fazzan requires active remote sensing using synthetic aperture radar instruments (JERS-1 SAR, RADARSAT, ENVISAT ASAR). This paper demonstrates how remote sensing, using both optical and radar instruments, has enabled mapping of palaeolake sediments in the Libyan Fazzan, and summarises the results of these investigations.