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TitleExtensive Early Cretaceous (Albian) methane seepage on Ellef Ringnes Island, Canadian High Arctic
AuthorWilisroft, K; Grasby, S E; Beauchamp, B; Little, C T S; Dewing, K; Birgel, D; Poulton, T; Hryniewicz, K
SourceGeological Society of America Bulletin vol. 129, no. 7-8, 2017 p. 788-805, https://doi.org/10.1130/b31601.1
Year2017
Alt SeriesEarth Sciences Sector, Contribution Series 20160337
PublisherGeological Society of America
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut
NTS69G; 69H; 69C; 69D; 69F; 69E; 79E; 79H
AreaEllef Ringnes Island
Lat/Long WENS-106.0000 -98.5000 79.5000 77.7500
Subjectsgas seeps; methane; isotope ratios; oxygen isotopes; stratigraphic traps; Albian; hydrate; biostratigraphy; Cretaceous
Illustrationslocation maps; geological sketch maps; photographs; stratigraphic charts; tables; plots; photomicrographs
ProgramWestern Cordillera, Regional porphyry transitions, GEM2: Geo-mapping for Energy and Minerals
AbstractDuring field mapping of Ellef Ringnes Island, Canadian Arctic Archipelago, 139 isolated Lower Cretaceous methane seep deposits were found from 75 field sites. Stable isotopes of the carbonates have values of d13C= -47permil to -35permil and d18O= -4.0permil to +0.7permil. As well, isoprenoids in organics from the seeps are significantly depleted in 13C, with the most negative d13C of = -118 permil and -113 permil for PMI and phytane/crocetane, respectively. These values indicate an origin through methane oxidation, consistent with biomarkers that are characteristic for anaerobic methanotrophic archaea within the seep deposits, accompanied by terminally-branched fatty acids sourced by sulphate-reducing bacteria, showing similar 13C values (-92permil). The seep deposits contain a moderate diversity macrofaunal assemblage containing ammonites, bivalves, gastropods, scaphopods, ''vestimentiferan'' worm tubes and brachiopods. The assemblage is dominated numerically by species that probably had chemosymbionts. The seep deposits formed in the subsurface with strong redox zones, in an otherwise normal marine setting, characterised by oxic waters at high paleolatitudes.While geographically widespread over an area of ~10,000 km2, seep deposits on Ellef Ringnes Island occur in a narrow stratigraphic
horizon, suggesting a large release of biogenic methane occurred over a brief period of time. This gas release was coincident with a transition from a cold to warm climate during the latest early Albian, and we hypothesize that this may have been related to gas hydrate release.
Summary(Plain Language Summary, not published)
As part of GEM mapping on the remote Ellef Ringnes Island, Nunavut, over 137 unusually carbonate mounds were discovered. These features were determined to be formed by an ancient release of methane gas into the seafloor at time of formation , ~107 million years ago. This corresponds with a shift in Earth climate from a cold to warm condition, suggesting that this climate warming may have been associated with destabilization of methane hydrates in the sea floor. Given that these were formed at a similar latitude as today the features can indicate the potential for methane hydrate destabilisation in relationship to modern climate warming.
GEOSCAN ID299684