Document Type

Article

Publication Date

1-8-2006

Abstract

In the 2,500,000 km²Take Chad Basin in central Afica, the 2000 Shuttle Radar ' Topographic Mission (SRTM) data haye been used to supplement the existing topographic data. SRTM data produce much sharper images of the region's topography and provide newinsights into debates about the nature and extent of 1ate Quatemary Lake Chad. This paper shows that t the accuracy of SRTM30, the recently released 30 arc seconds topographic data from SRTM, largely surpasses that of previous global Digital Elevation Models (DEMs) available D the region. Using GIS we i idcntificd from SRTM30 elevation data key features in the landscape topography providing further evidence for the existence of a Megalake Chad. The SRTM30 data corroborate the presence of two ancient shorelines ssociated with stillstands of t "the paleolake at the elevation Of the Mayo Kebbi and Bahr Ghazal spillovers. We found a general flattening of the topography in the region covered by Megalake Chad which is most likely r the result of wave-cut action. The SRTM30 data show that the remains of the highest paleoshoreline have a constant elevation of 325+5 m ams]. At its maximum extent, Megalake Chad had an area f about 340 000 km (only 8% less than the present-day world's largest lake, the Caspian Sea). The SRTM30 data also revealed ancient drainage networks n the Sahara that lead to Megalake Chad. We compiled available 14C dates to constrain Holocene Megalake Chad events. The results presented in this paper have significant consequences for improving our knowledge of regional paleohydrology and continental climate change. This study is also the first step for a GIS-based reconstruction of late Quaternary paleohydrology tropical Africa.

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