GEOMORPHOSITES OF TOZEUR REGION (SOUTH-WEST TUNISIA)

Abstract

: J. De Waele et al., Geomorphosites of Tozeur region (south-west Tunisia). (IT ISSN 0394-3356, 2005).
Tozeur is the most important tourist town of south-western Tunisia, situated in between the two salt lakes Chott El Djerid to the south
and Chott El Gharsa to the north. This area is known for its luxuriant oasis in the middle of the desert (Tozeur, Gafsa, Nefta etc.), the
mountain chains to the north close to the border with Algeria with its villages and waterfalls (Tameghza, Chebìka, Midès), the mountain chain east of Tozeur (Jbel Morra etc.) with its arid canyons, and the wide salt plains (Chotts). Tourists usually visit the region rapidly without staying overnight, overlooking and ignoring the great geomorphologic and geological interesting places and landscapes.
Therefore, in the framework of a Research Project performed by the Department of Geology of the University of Cagliari in collaboration with the Institut des Régions Arides at Medenine and with the "Faculté de Sciences Humaines et sociales" of Tunis and financed by the Sardinian Regional Government (R.L. 11 Aprile 1996, n° 19), our multidisciplinary Research Team has studied twenty-one geosites and geological landscapes in the region of Tozeur, with the purpose of constituting a network of geosites in these arid and semiarid areas.
Field work combined with remote sensing techniques have enabled to start preparing thematic maps of these geosites which,
together with their description (genesis, evolution, state of conservation, proposals of valorisation, etc.) will be useful for obtaining
financial aid for their protection and valorisation. The definition of morphostructural units landform analysis at a large/medium scale
was performed by TeleGIS Laboratory, involved in these studies on southern Tunisia from 1997 in collaboration with the Institute des
Régions Arides, applying remote sensing techniques on multi-spectral satellite images. During this project the interpretation keys for
the image classification were created in the different steps of field observations and digital image processing. The radiometric and
geometric responses were used for the discrimination of spectral units (lithological sequences) and textural units defined by photointerpretation techniques (structural and landscape units like anticlines, fault-controlled valleys or forms like chevron, etc.).
Many of the studied geomorphosites are represented by canyons (Gorges de Ben Nebhana, Sidi Bou Helal, Thelja, En Negueb,
Chaabet Es Sfa, Ben Hamed, Midès, etc.) and waterfalls (Grande Cascade and Cascade de l'Oasis at Tameghza, Cascade de
Chebìka and its geological-structural features). Others are related to aeolian and meteoric processes (Barchan dunes of El Ghadayer,
morpho-sculpture of Ong El Jmel, Yardangs of El Ghadayer, Nebkha fields of Chamsa). The remaining geosites are an ancient lacustrine coastline testified by a lumachelle with Cardium in the Jehim oasis near Tozeur, the anticline of Brikis close to Tameghza, and
an ancient phosphate mine at Chouabin (Jbel Chouabin close to Redeyef), a representative part of Chott el Djerid, the Delta of Oued
Mellah and the alluvial cone of Oued Foum el Khanga and the ancient oasis (Corbeille) of Nefta.
These sites and landscapes of geological and geomorphological interest represent the entire geological history of the Tozeur and the
Chotts region fairly well. This history starts from Early Cretaceous, and the various sites narrate the sedimentary and tectonic events,
the palaeo-environmental and palaeo-climate episodes, the birth, development and extinction of animal and plant species, the geomorphological processes and depositional events, explaining the present morphology, climate and landscape in a most interesting
scientific and educational way.
The linking of all these places of geological and geomorphologic interest in networks of Geosites along a thematic issue (the "Living
Desert" network with Nebkha and Barchan dunes, Yardangs and Aeolian sculptures, the "Rocks and Water" network with waterfalls,
mountains and canyons, the "Earth’s Memory" network across the canyons of Jbel Morra-Sidi Bou Helal passing through more than
100 million years of Earth's geological history, the “Phosphate Route” network with active and abandoned phosphate mines and their
environmental impact and the “Changing Environment and Climate” network with salt pans, fossil shorelines and abandoned oasis)
give an interesting opportunity of telling the history of the Earth, promoting geology and geomorphology to the local people and to the visitors. In fact, geological heritage can and should become a cultural and economical resource for the local people, and therefore
these inhabitants should be taught understanding their natural and cultural environment, enabling them to use these elements in the
framework of a touristic and sustainable development of their region.