TY - JOUR

T1 - Microbial dominated Ca-carbonates in a giant Pliocene cold-seep system

T2 - (Crotone Basin – South Italy)

AU - Perri, Edoardo

AU - Borrelli, Mario

AU - Heimhofer, Ulrich

AU - Umbro, Bruno

AU - Santagati, Pierluigi

AU - Le Pera, Emilia

N1 - Publisher Copyright: © 2024 International Association of Sedimentologists.

PY - 2024/9/17

Y1 - 2024/9/17

N2 - The Pliocene cold-seep carbonate of the Crotone Basin (South Italy) represents a key site for dimension, outcropping exposure and quality. These deposits form a large carbonate (calcite) body (350 m long, 100 m wide and 40 m thick), and are characterized by a conduit facies made of authigenic calcite interpreted as previously active gas/fluid escape pipes and by a pavement facies, depicted as the surrounding early calcite-cemented bioclastic and siliciclastic sediments. Pavement facies are commonly colonized by chemosymbiotic and non-chemosymbiotic macrofauna (Lucinid and Solemyid bivalves, gastropods and serpulids). The conduit microfacies is characterized by the inward accretion of dark micritic laminae alternating with whitish sparitic layers. The micritic laminae show a microbial peloidal to dendrolitic fabric, which commonly incorporates planktonic foraminifera and coprolites, whereas the crystalline layers consist of microsparitic and sparitic crusts of prismatic zoned calcite crystals. The pavement facies shows more variability, because it is typified by laminated microbial boundstones, chemosymbiotic–bivalves packstone, foraminiferal packstone/wackestone and hybrid arenites. The stratigraphic constraint coupled with the foraminiferal assemblage (planktonic taxa) suggest a deep-water setting occasionally affected by siliciclastic sedimentary flows. The pavement facies also shows common brecciation features, suggesting the establishment of post-depositional overpressure conditions due to the early cementation of the conduits, which triggered localized rock failure. Stable isotope analysis of the different facies reveals overall negative δ13C values (−6.8 to −37.4‰ Vienna PeeDee Belemnite), indicating the presence of a complex mixture of methane with other hydrocarbons consumed microbially via anaerobic oxidation of methane; whereas δ18O is relatively positive (0.0 to 3.4‰ Vienna PeeDee Belemnite) suggesting the possible dehydration of clay minerals and/or destabilization of gas hydrates. This study, besides helping in the definition of the migration pathways and modality of accumulation of hydrocarbon-rich fluids, can also help in building more and more realistic models for the complex genesis of cold-seep carbonates.

AB - The Pliocene cold-seep carbonate of the Crotone Basin (South Italy) represents a key site for dimension, outcropping exposure and quality. These deposits form a large carbonate (calcite) body (350 m long, 100 m wide and 40 m thick), and are characterized by a conduit facies made of authigenic calcite interpreted as previously active gas/fluid escape pipes and by a pavement facies, depicted as the surrounding early calcite-cemented bioclastic and siliciclastic sediments. Pavement facies are commonly colonized by chemosymbiotic and non-chemosymbiotic macrofauna (Lucinid and Solemyid bivalves, gastropods and serpulids). The conduit microfacies is characterized by the inward accretion of dark micritic laminae alternating with whitish sparitic layers. The micritic laminae show a microbial peloidal to dendrolitic fabric, which commonly incorporates planktonic foraminifera and coprolites, whereas the crystalline layers consist of microsparitic and sparitic crusts of prismatic zoned calcite crystals. The pavement facies shows more variability, because it is typified by laminated microbial boundstones, chemosymbiotic–bivalves packstone, foraminiferal packstone/wackestone and hybrid arenites. The stratigraphic constraint coupled with the foraminiferal assemblage (planktonic taxa) suggest a deep-water setting occasionally affected by siliciclastic sedimentary flows. The pavement facies also shows common brecciation features, suggesting the establishment of post-depositional overpressure conditions due to the early cementation of the conduits, which triggered localized rock failure. Stable isotope analysis of the different facies reveals overall negative δ13C values (−6.8 to −37.4‰ Vienna PeeDee Belemnite), indicating the presence of a complex mixture of methane with other hydrocarbons consumed microbially via anaerobic oxidation of methane; whereas δ18O is relatively positive (0.0 to 3.4‰ Vienna PeeDee Belemnite) suggesting the possible dehydration of clay minerals and/or destabilization of gas hydrates. This study, besides helping in the definition of the migration pathways and modality of accumulation of hydrocarbon-rich fluids, can also help in building more and more realistic models for the complex genesis of cold-seep carbonates.

KW - Authigenic carbonates

KW - chemosymbiotic fauna

KW - cold seep

KW - conduit

KW - microbialites

KW - pavement

UR - http://www.scopus.com/inward/record.url?scp=85188148087&partnerID=8YFLogxK

U2 - 10.1111/sed.13192

DO - 10.1111/sed.13192

M3 - Article

AN - SCOPUS:85188148087

VL - 71

SP - 1767

EP - 1794

JO - SEDIMENTOLOGY

JF - SEDIMENTOLOGY

SN - 0037-0746

IS - 6

ER -