Simultaneous extensional exhumation across the Alboran Basin: Implications for the causes of late orogenic extension
- 1Research School of Earth Sciences at University College London—Birkbeck, Gower Street, London WC1E 6BT, UK
- 2Laboratory for Isotope Geology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden
- 3Department of Earth Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA, UK
- 4Research School of Earth Sciences at University College London—Birkbeck, Gower Street, London WC1E 6BT, UK
- 5Research School of Earth Sciences at University College London—Birkbeck, Gower Street, London WC1E 6BT, UK
Abstract
Large-scale crustal thinning of the Alpine orogen in the westernmost Mediterranean (Alboran Sea and surrounding regions) was rapid, simultaneous over an area of 60,000 km2, and took place ∼25 m.y. after the main crustal thickening event. Crustal thinning, which locally exposed subcontinental mantle, was accompanied by high-grade metamorphism and partial melting. Both U-Pb dating of zircon and thermal modeling of cooling histories indicate that the thermal peak was reached between 23 and 21 Ma over the entire region. Final exhumation and cooling followed immediately. Possible explanations for this dramatic late orogenic extension include subduction rollback, slab detachment, lithospheric delamination, and convective removal of subcontinental lithosphere. Of these processes, only convective removal of subcontinental lithosphere predicts a significant time lapse between crustal thickening and the onset of extension, the simultaneity of extension over the whole region, and heating of rock during rapid exhumation to produce the high-grade metamorphic event.
Footnotes
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↵GSA Data Repository item 2003024, Tables DR1–DR4, U-Th-Pb, Ar-Ar, and fission-track data on zircons and on apatites, is available from Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, editinggeosociety.org, or at http://www.geosociety.org/pubs/ft2003.htm.
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- Accepted October 25, 2002.
- Received June 26, 2002.
- Revision received October 24, 2002.
- Geological Society of America
