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The enigmatic Chad lineament revisited with global gravity and gravity-gradient fields

By
Carla Braitenberg
Carla Braitenberg
Dipartimento di Geoscienze, Università di Trieste, via Weiss 1, 34100 Trieste, Italy
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Patrizia Mariani
Patrizia Mariani
Dipartimento di Geoscienze, Università di Trieste, via Weiss 1, 34100 Trieste, Italy
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Jörg Ebbing
Jörg Ebbing
Geological Survey of Norway (NGU), Leiv Eirikssons vei 39, 7491 TrondheimDepartment of Petroleum Engineering and Applied Geophysics, NTNU, 7491 Trondheim, Norway
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Michal Sprlak
Michal Sprlak
Dipartimento di Geoscienze, Università di Trieste, via Weiss 1, 34100 Trieste, ItalyResearch Institute of Geodesy and Cartography, Chlumeckého 4, 826 62 Bratislava, Slovakia
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Published:
January 01, 2011

Abstract

The crustal structure of northern Africa is puzzling, large areas being of difficult access and concealed by the Sahara. The new global gravity models are of unprecedented precision and spatial resolution and offer a new possibility to reveal the structure of the lithosphere beneath the Sahara. The gravity gradients correlate better than gravity with geological features such as rifts, fold belts and magmatic deposits and intrusions. They are an ideal tool to follow geological units (e.g. basement units) below a stratigraphic layer of varying density (e.g. sediments). We focus on the Chad lineament, a 1300 km arcuate feature located between the west and central African rift system. The gravity fields show differences between the lineament and the west and central African rift system. Along the centre of the lineament high-density rocks must be present, which relate to either magmatic or metamorphic rocks. This is very different to the lineaments of the western and central-west African rift system which are filled with sediments. Considering present models of rifting and the absence of topography, the lineament cannot be coeval to the west and central African rift system and is most likely older. We suggest that the lineament is a structural element of the Saharan Metacraton.

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Contents

Geological Society, London, Special Publications

The Formation and Evolution of Africa: A Synopsis of 3.8 Ga of Earth History

D. J. J. Van Hinsbergen
D. J. J. Van Hinsbergen
University of Oslo, Norway
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S. J. H. Buiter
S. J. H. Buiter
Geological Survey of Norway
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T. H. Torsvik
T. H. Torsvik
University of Oslo
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C. Gaina
C. Gaina
Geological Survey of Norway
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S. J. Webb
S. J. Webb
University of the Witwatersrand, South Africa
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Geological Society of London
Volume
357
ISBN electronic:
9781862396050
Publication date:
January 01, 2011

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