Orbital forcing recorded in subtidal cycles from a Lower Miocene siliciclastic–carbonate ramp system (Central Italy) |
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Authors: | Marco Brandano Laura Corda Goffredo Mariotti |
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Institution: | Dipartimento Scienze della Terra, Universitàdi Roma 'La Sapienza', Piazzale Aldo Moro 5, Rome 00185, Italy;;Istituto di Geologia Ambientale e Geoingegneria-CNR, Rome, Italy |
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Abstract: | Metre-scale siliciclastic–carbonate cycles are the basic depositional motif of the lower Miocene Guadagnolo Formation outcropping in the central Apennines. The mechanisms which formed the mixed-lithology cycles are still a matter of debate. The mixed siliciclastic–carbonate system discussed in this paper provides a new case study to illustrate the role of orbital forcing in controlling the facies evolution and cyclic stacking of small-scale sequences deposited on the outer sector of a ramp. Two sections are discussed that display mixed siliciclastics and carbonates arranged in upward-shallowing cycles. Each cycle shows an upward decrease in the terrigenous input and a parallel increase in benthic fauna. Time-series analyses indicate the cyclic carbonate-terrigenous pattern to be largely controlled by orbital forcing in the Milankovitch frequency band. Coupling of climate change and sea-level fluctuations in tune with orbital cycles are proposed as driving mechanisms. |
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