Jurassic magnetostratigraphy, 1. Kimmeridgian-Tithonian of Sierra Gorda and Carcabuey,southern Spain |
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| Authors: | JG Ogg MB Steiner F Oloriz JM Tavera |
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| Institution: | 1. Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071U.S.A.;2. A-012, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093U.S.A.;3. Departamento de Paleontologia, Universidad de Granada, Granada Spain;4. Departamento de Geologia General, Universidad de Granada, Granada, Spain |
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| Abstract: | Two coeval sections of red to white ammonite-rich pelagic limestones spanning the complete Kimmeridgian and most of the Tithonian were sampled in detail. All samples were treated by progressive thermal demagnetization to remove a present field overprint. Characteristic magnetization is carried primarily by magnetite. Polarity intervals are easily identified and correlate well between the two sections. The Tithonian polarity sequence can also be correlated to sections in northern Italy. The similarity between the polarity sequence and the M-sequence of marine magnetic anomalies, coupled with the precise biostratigraphic control, allows assignment of the following ages to the M-sequence: the Late/Early Tithonian boundary is correlated to the end of M-20, the Tithonian/Kimmeridgian boundary to the end of M-23, the Late/Early Kimmeridgian boundary to the latter part of M-24, and the Kimmeridgian/Oxfordian boundary within or slightly after M-25.The mean directions of characteristic magnetization have α95's less than 3° and demonstrate extensive differential block rotation within the Subbetic province. Paleolatitudes during the Kimmeridgian/Tithonian are in the range of 16–24°N. |
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