Early Cretaceous methane seepage system and associated carbonates, biota and geochemistry, Sverdrup Basin, Ellef Ringnes Island, Nunavut

Over one hundred carbonate deposits, interpreted as having formed at methane seepage sites in the Sverdrup Basin have been discovered on Ellef Ringnes Island, Canadian Arctic. The deposits, up to 2.7 metres tall and 60 metres wide, are found within the lower member of the Lower Cretaceous Christophe...

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Bibliographic Details
Main Author: Williscroft, Krista
Other Authors: Beauchamp, Benoit, Grasby, Stephen
Format: Master Thesis
Language:English
Published: Graduate Studies 2013
Subjects:
Biogeochemistry
Geochemistry
Geology
Arctic
Methane
Seep
Carbonate
Ellef
Ringnes
Nunavut
Ellef Ringnes Island
arctic methane
sverdrup basin
Online Access:http://hdl.handle.net/11023/1102
https://doi.org/10.11575/PRISM/25767
Description
Summary:Over one hundred carbonate deposits, interpreted as having formed at methane seepage sites in the Sverdrup Basin have been discovered on Ellef Ringnes Island, Canadian Arctic. The deposits, up to 2.7 metres tall and 60 metres wide, are found within the lower member of the Lower Cretaceous Christopher Formation, a silty marine shale. The carbonates have complex and heterogeneous structures typical of seep carbonates, including banded botryoidal and clotted textures as well as void filling sparite. Stable carbon isotopes show highly 13C-depleted values, as low as δ13CVPDB = -53‰, indicative of authigenic carbonate precipitation via the anaerobic oxidation of biogenic methane. Abundant and well-preserved fauna include multiple species of bivalves, worm tubes, ammonites and gastropods. Methane seepage is calculated to have lasted ~500,000 years and was brought about by a tensional stress regime as well as salt diapirism related faulting.

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