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

• 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

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.