The Paola Ridge is a NNW–SSE 60-km-long anticline, in the south-eastern sector of the Tyrrhenian Sea (Paola Basin), that is characterized by the presence of pockmarck-punctuated mud diapirs and mud volcanoes characterized by... [ view full abstract ]
The Paola Ridge is a NNW–SSE 60-km-long anticline, in the south-eastern sector of the Tyrrhenian Sea (Paola Basin), that is characterized by the presence of pockmarck-punctuated mud diapirs and mud volcanoes characterized by active gas venting, all of them connected with extensional NW-SE to NNW-SSE trending faults. The MVP11and MarBeep oceanographic cruises were carried in 2011 and 2014 on board the R/V CNR Urania, in order to characterize those cold seep structures in the study area. During the cruises, multi-beam bathymetric data, CHIRP profiles, gravity coring and box coring samples were acquired to define the sedimentological, petrographical, mineralogical and geochemical characteristics of the marine sediments draping the mud mobile structures. We have analyzed different kind of samples (rocks/sediments): limestone crusts, carbonates of tubular form, iron oxy-hydroxide crusts, pyrite and sulfur crusts and cohesive mud. Each sample has been analyzed by means of optical petrography, XRD, SEM-EDS, XRF, ICP-AES and ICP-MS. Selected samples were chosen for carbon, oxygen and sulfur isotopic analyses.
Authigenic calcite and aragonite, associated with chemosymbiotic bivalve assemblages, were discovered on pockmarks along faults cutting mud diapirs. Stable isotopes (C and O) on these carbonates resulted to be depleted in δ13C and slightly enriched in δ18O, suggesting that authigenic carbonates were likely deriving from bacterial oxidation of methane.
Several sites were sampled over the mud volcanoes. Iron oxy-hydroxide crusts, mainly consisting of goethite, were found on the seafloor. Pyrite and sulfur crusts showed a mineralogical composition consisting of pyrite and /or sphalerite, quartz and few feldspars. Tubular authigenic carbonates contained siderite, quartz and few phyllosilicates. Stable isotopes (C and O) of the siderite showed enrichment in both carbon and oxygen.
Cohesive mud samples were dominated by quartz, halite, feldspars, muscovite and clay minerals (illite, vermiculite, chlorite, kaolinite), while in some samples the presence of calcite or dolomite, siderite, hematite and pyrite was recognized.
All the samples were analyzed for their chemical composition: major, minor, trace elements, including rare earth elements (REE) for reconstructing their provenance and chemical properties of the source area which are important for their formation and their relationships with mineralogical composition.
Topics: Chemical sedimentary processes , Topics: Microbial activity as sedimentary process , Topics: Diagenesis
