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Authigenic carbonates in upper Miocene sediments of the Tertiary Piedmont Basin (NW Italy); vestiges of an ancient gas hydrate stability zone?

Francesco Dela Pierre, Luca Martire, Marcello Natalicchio, Pierangelo Clari and Catalin Petrea
Authigenic carbonates in upper Miocene sediments of the Tertiary Piedmont Basin (NW Italy); vestiges of an ancient gas hydrate stability zone?
Geological Society of America Bulletin (July 2010) 122 (7-8): 994-1010

Abstract

A wide array of carbonate-rich rocks has been recognized in the Tertiary Piedmont Basin (NW Italy), hosted in lower Messinian slope deposits. Carbonate cements show negative delta (super 13) C values and positive delta (super 18) O values, suggesting that carbonate precipitation was induced by microbial degradation of methane produced from gas hydrate destabilization. Two groups of rocks have been distinguished: (1) Lucina-bearing mud breccias, representing the seafloor product of an ancient seepage site; and (2) Lucina-free concretions, originating below the sediment-water interface. Within this group, two subtypes have been further distinguished: stratiform concretions and cylindrical concretions. Stratiform concretions result from precipitation of dolomite in the pores of muddy sediments. Some of them display a brecciated structure; others show a network of septarian-like cracks that are empty, filled with sediments, or zoned carbonate cements. Their internal features are related to the formation of gas hydrates within the sediments and to their destabilization. Thus, these rocks mark a portion of the sedimentary column located within a (paleo) gas hydrate stability zone. Cylindrical concretions represent ancient fluid conduits related to the upward migration of CH (sub 4) -rich fluids subsequent to gas hydrate destabilization. The carbonate-rich rocks of the Tertiary Piedmont Basin stand as one of the first examples of methane-derived rocks that record successive episodes of dissociation and re-formation of gas hydrates, and they provide precious elements to model the general evolution of a portion of the sedimentary column located within the hydrate stability zone.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 7-8
Title: Authigenic carbonates in upper Miocene sediments of the Tertiary Piedmont Basin (NW Italy); vestiges of an ancient gas hydrate stability zone?
Affiliation: Universita di Torino, Dipartimento di Scienze della Terra, Turin, Italy
Pages: 994-1010
Published: 201007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 84
Accession Number: 2010-050181
Categories: StratigraphySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, geol. sketch map
N44°46'60" - N44°49'60", E08°54'00" - E08°56'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201027
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