Genetic link between Miocene seafloor methane seep limestones and underlying carbonate conduit concretions at Rocky Knob, Gisborne, New Zealand

Nelson, Campbell S., Campbell, Kathleen A., Nyman, Stephanie L., Greinert, Jens, Francis, David A. and Hood, Steven D. (2019) Genetic link between Miocene seafloor methane seep limestones and underlying carbonate conduit concretions at Rocky Knob, Gisborne, New Zealand New Zealand Journal of Geology and Geophysics . DOI 10.1080/00288306.2018.1561474.

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Abstract

Methane-derived authigenic carbonates (MDACs) in Miocene bathyal mudstones in North Island, New Zealand are typically expressed as either sub-seafloor conduit concretions or as seafloor seep limestones, but rarely are both types exposed in outcrop at one locality. Consequently, any potential genetic link between them is usually inferred. This also appears to be the case for global occurrences of MDAC. At the Rocky Knob seep complex near Gisborne both seep limestones and conduit concretions co-occur. The petrography and stable carbon (δ13C) and oxygen (δ18O) isotope compositions of their various authigenic carbonate components (automicrite, fibrous aragonite crystals, and granular, blocky and bladed calcite crystals) show that distinctive isotope and petrographic groupings for precipitates within the conduit concretions match or “correlate” with several of those in the seep limestones. This corroborates their genetic tie and derivation from the same fluids, albeit in different parts (i.e. sub-seafloor vs. seafloor) of the seep complex.

Document Type: Article
Keywords: Fossiliferous seep limestone, methane-derived authigenic carbonate (MDAC), micrite, middle Miocene, Rocky Knob, East Coast Basin, New Zealand, seep plumbing network, stable carbon and oxygen isotopes, tubular conduit concretions
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.1080/00288306.2018.1561474
ISSN: 0028-8306
Date Deposited: 11 Feb 2019 08:24
Last Modified: 11 Feb 2019 10:20
URI: http://eprints.uni-kiel.de/id/eprint/45771

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