In the Crotone Basin, a Neogene cold seep carbonate body (Calcari a Lucina) with a thickness of 40 m and a length of 350 m crops out. It is characterized by a conduit facies made of authigenic carbonates filling the previously active gas/fluid escape pipes and a pavement facies made of early carbonate-cemented bioclastic and siliciclastic sediments colonized by a chemosynthetic macrofauna such as Lucinids, tubeworms and gastropods. The conduit facies shows the inward accretion of dark micritic laminae alternated to clear crystalline layers. The micritic laminae are typified by microbial peloidal to dendrolitic fabric incorporating planktonic foraminifera and coprolites. Whereas the crystalline layers show microspar laminae and sparry crusts made of prismatic zoned calcite crystals. The pavement facies is characterized by planktonic foraminiferal bioturbated mudstone/wackestones passing to mixed carbonate-siliciclastic arenites. The foraminiferal assemblage together with the relative proportion of sandy/silty grains suggest a deep-water setting with occasional siliciclastic coarser sedimentary flows. Moreover, in the pavement facies, brecciation is very common, possibly indicating the overpressure conditions established by the gas/fluid injection. Stable Isotopes analysis in all the studied facies revealed negative values of δ13C (-12 to -38‰) and an enrichment in δ18O (0.83 to 3.4‰) reflecting the destabilization of gas hydrates probably made of thermogenic methane.
Cold seep carbonates in the Crotone Basin (South Italy)
Mario Borrelli
;Bruno Umbro;Pierluigi Santagati;Emilia Le Pera;Edoardo Perri
2022-01-01
Abstract
In the Crotone Basin, a Neogene cold seep carbonate body (Calcari a Lucina) with a thickness of 40 m and a length of 350 m crops out. It is characterized by a conduit facies made of authigenic carbonates filling the previously active gas/fluid escape pipes and a pavement facies made of early carbonate-cemented bioclastic and siliciclastic sediments colonized by a chemosynthetic macrofauna such as Lucinids, tubeworms and gastropods. The conduit facies shows the inward accretion of dark micritic laminae alternated to clear crystalline layers. The micritic laminae are typified by microbial peloidal to dendrolitic fabric incorporating planktonic foraminifera and coprolites. Whereas the crystalline layers show microspar laminae and sparry crusts made of prismatic zoned calcite crystals. The pavement facies is characterized by planktonic foraminiferal bioturbated mudstone/wackestones passing to mixed carbonate-siliciclastic arenites. The foraminiferal assemblage together with the relative proportion of sandy/silty grains suggest a deep-water setting with occasional siliciclastic coarser sedimentary flows. Moreover, in the pavement facies, brecciation is very common, possibly indicating the overpressure conditions established by the gas/fluid injection. Stable Isotopes analysis in all the studied facies revealed negative values of δ13C (-12 to -38‰) and an enrichment in δ18O (0.83 to 3.4‰) reflecting the destabilization of gas hydrates probably made of thermogenic methane.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
