Open AccessBivalve shell horizons in seafloor pockmarks of the last glacial‐interglacial transition: a thousand years of methane emissions in the A rctic O cean
Author(s) -
Ambrose William G.,
Panieri Giuliana,
Schneider Andrea,
PlazaFaverola Andreia,
Carroll Michael L.,
Åström Emmelie K. L.,
Locke William L.,
Carroll JoLynn
Publication year - 2015
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2015gc005980
Subject(s) - authigenic , geology , seafloor spreading , cold seep , chemosynthesis , petroleum seep , methane , pyrite , foraminifera , paleontology , anaerobic oxidation of methane , deep sea , interglacial , geochemistry , glacial period , oceanography , sediment , hydrothermal vent , hydrothermal circulation , benthic zone , chemistry , organic chemistry
We studied discrete bivalve shell horizons in two gravity cores from seafloor pockmarks on the Vestnesa Ridge (∼1200 m water depth) and western Svalbard (79°00′ N, 06°55′ W) to provide insight into the temporal and spatial dynamics of seabed methane seeps. The shell beds, dominated by two genera of the family Vesicomyidae: Phreagena s.l. and Isorropodon sp., were 20–30 cm thick and centered at 250–400 cm deep in the cores. The carbon isotope composition of inorganic (δ 13 C from −13.02‰ to +2.36‰) and organic (δ 13 C from −29.28‰ to −21.33‰) shell material and a two‐end member mixing model indicate that these taxa derived between 8% and 43% of their nutrition from chemosynthetic bacteria. In addition, negative δ 13 C values for planktonic foraminifera (−6.7‰ to −3.1‰), concretions identified as methane‐derived authigenic carbonates, and pyrite‐encrusted fossil worm tubes at the shell horizons indicate a sustained paleo‐methane seep environment. Combining sedimentation rates with 14 C ages for bivalve material from the shell horizons, we estimate the horizons persisted for about 1000 years between approximately 17,707 and 16,680 years B.P. (corrected). The seepage event over a 1000 year time interval was most likely associated with regional stress‐related faulting and the subsequent release of overpressurized fluids.