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Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy)

Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
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Geosciences 2019, 9(3), 134; https://doi.org/10.3390/geosciences9030134
Received: 25 February 2019 / Revised: 14 March 2019 / Accepted: 15 March 2019 / Published: 20 March 2019
(This article belongs to the Special Issue Gas Hydrate: Environmental and Climate Impacts)
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Abstract

The occurrence of seep-carbonates associated with shallow gas hydrates is increasingly documented in modern continental margins but in fossil sediments the recognition of gas hydrates is still challenging for the lack of unequivocal proxies. Here, we combined multiple field and geochemical indicators for paleo-gas hydrate occurrence based on present-day analogues to investigate fossil seeps located in the northern Apennines. We recognized clathrite-like structures such as thin-layered, spongy and vuggy textures and microbreccias. Non-gravitational cementation fabrics and pinch-out terminations in cavities within the seep-carbonate deposits are ascribed to irregularly oriented dissociation of gas hydrates. Additional evidences for paleo-gas hydrates are provided by the large dimensions of seep-carbonate masses and by the association with sedimentary instability in the host sediments. We report heavy oxygen isotopic values in the examined seep-carbonates up to +6‰ that are indicative of a contribution of isotopically heavier fluids released by gas hydrate decomposition. The calculation of the stability field of methane hydrates for the northern Apennine wedge-foredeep system during the Miocene indicated the potential occurrence of shallow gas hydrates in the upper few tens of meters of sedimentary column. View Full-Text
Keywords: gas hydrates; seep-carbonates; clathrites; Miocene; northern Apennines gas hydrates; seep-carbonates; clathrites; Miocene; northern Apennines
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Argentino, C.; Conti, S.; Fioroni, C.; Fontana, D. Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy). Geosciences 2019, 9, 134.

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