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2007

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cc by-sa (c) Calvet et al., 2007
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/16879

Fifth-order cyclicity and organic matter contents relationship (Lower Eocene, Pyrenees)

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The Upper Limestone Member of the Corones Formation of the Spanish Pyrenees consists of various units (Lower and Upper Foraminifera Units, Shale Unit, Cherty-ostracode Unit, Ostracode Unit and Chara-ostracode Unit) and offers strong facies and lateral thickness (20 to 80 m) variations. Detailed facies analyses, fifth-order cycles and organic geochemical determinations in the central domain of the Corones platform carbonates (Cherty-ostracode Unit), lower Eocene in age, were carried out to establish a case of close relationship between variations in organic matter productivity and cyclicity with annual period. The Cherty-ostracode Unit displays a continuous and pervasive fifth-order cyclicity, represented by 5 cycles. Each cycle consists of a lower part (mollusc facies) and an upper part (laminated ostracode facies). The calculated fifth-order cycle period ranges from about 17,000 to 28,000 years, which falls within the Milankovitch Band. Variations in organic matter content related to these carbonate cycles have been established. The lower mollusc facies members show a low organic carbon content and Hydrogen Index (HI) below 0.6% in weight and 261, respectively. By contrast, the upper laminated ostracode facies members show high organic carbon contents (up to 2% in weight) and high HI (between 164 and 373), and are also characterized by important silicification processes (the content in chert is up to 30%). The organic geochemistry resulting from these organic rich levels reflects a contribution of algal marine input.

Matèries

Geoquímica orgànica, Eocè, Pirineus

Matèries (anglès)

Organic geochemistry, Eocene Epoch, Pyrenees

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Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

Citació

CALVET, F. (Francesc), et al. Fifth-order cyclicity and organic matter contents relationship (Lower Eocene, Pyrenees). Geologica Acta. 2007. Vol. 5, num. 1, pags. 59-75. ISSN 1695-6133. [consulted: 4 of August of 2026]. Available at: https://hdl.handle.net/2445/16879

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