image: 'Pipe-Rock' (with Skolithos) of lower Middle Cambrian age unconformity covering the Saharide basement in Jabal ben Ghanimah, Libya view more
Credit: Image credit: A. M. Celâl ?engör.
A study finds that an ancient mountain belt formed 500-900 million years ago across the Arabian-Nubian Shield and Sahara Desert before the final collision of east and west Gondwana-Land. The origins of mountain belts formed by plate tectonics are typically determined by analyzing fossils located within their strata. However, the limited fossil record of the Precambrian area renders analysis of tectonic plate movement difficult. A. M. Celal Sengor and colleagues reconstructed the tectonic environments of North Africa and the Arabian Peninsula and report the formation of an ancient mountain belt, the Saharides, 500-900 million years ago, before the final collision of east and west Gondwana-Land. To identify essential mountain-building processes, the authors examined the geochemistry and structural geology of the existing Precambrian rock record and attempted to distinguish juvenile from reworked crust material. The samples were not discrete but part of a belt of mountains formed over a 400 million year period by subduction and accretion of rocks that simultaneously became stacked by strike-slip faults into large crustal panels. Analysis of magnetic anomalies suggested that the mountain belt may have been bent twice after its formation, similar to the Hercynian double orocline in western Europe. The Saharides' formation likely added 3-5 million km2 of material to the continents. According the authors, the method could be used to reconstruct other complex mountain formations, or orogenic systems.
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Article #20-15117: "Reconstructing orogens without biostratigraphy: The Saharides and continental growth during the final assembly of Gondwana-Land," by A. M. Celal Sengor, Nalan Lom, Cengiz Zabc?, Gursel Sunal, and Tayfun Oner.
MEDIA CONTACT: A. M. Celal Sengor, Istanbul Technical University, TURKEY; e-mail: <sengor@itu.edu.tr>
Journal
Proceedings of the National Academy of Sciences