Energy in Canada's North

Ichnological Expressions of Low Oxygen Settings: An Integrated Ichnological and Sedimentological Analysis of the Canol Formation, Northwest Territories, Canada

Soapbox Wednesday, November 21, 2018 - 13:21 to 13:27 Theatre 3


S.K. Biddle (Presenting)
University of Alberta

M.T. LaGrange Rao
University of Alberta

B. Harris
University of Alberta

K.M. Fiess
NWT Geological Survey

V. Terlaky
NWT Geological Survey

M.K. Gingras
University of Alberta

The Canol Formation, part of the Horn River Group in the Northwest Territories, primarily consists of black shales deposited during the late Givetian to early Frasnian ages of the Middle and Late Devonian epochs. The Canol Formation is considered to represent distal basin fill accumulated in an anoxic to euxinic depositional setting, owing to the shale’s organic-rich character, pyrite content, and lack of obvious biogenic reworking. The sediment transport processes resulting in the deposition of these shales have yet to be identified. This study aims to identify depositional processes and paleo-redox fluctuations within the Canol Formation via comprehensive integrated ichnological and sedimentological analyses and some integration with geochemical paleo-redox proxies.

Detailed ichnological and sedimentological petrographic analyses are carried out on thin sections taken from several cored Canol Formation intervals (MGM Shell East Mackay I-78, Husky Little Bear N-09 and H-64, and ConocoPhillips Mirror Lake N-20 and Loon Creek O-06) and outcrop localities (Mountain River, Carcajou River, Dodo Canyon, Powell Creek, and Rumbly Creek). Initial investigation has led to the identification of biogenic-sedimentary structures (i.e. ichnofossils) throughout the Canol intervals. Identified traces are grouped into a morphological classification scheme based on characteristics such as orientation, structure fill and fill organization, and burrow linings. Six morphologically separate ichnofossils have been documented. Three morphotypes are classified as vertical burrows, and include relatively small sinuous vertical traces, inclined-to-vertical unlined meniscate-backfilled traces, and fugichnia. Three morphotypes display horizontal orientations, and include tubular lined traces with organized fill, tubular unlined traces with homogenized fill, and relatively small sinuous horizontal burrows. Bioturbation intensities range from unburrowed to heavily bioturbated, with sinuous vertical traces being the most commonly documented.

Primary sedimentary structures being evaluated include, but are not limited to, evidence of small-scale features such as bedding and lamination, and diagenetic features such as pyrite abundance and habit. Integration of geochemical data collected for paleo-redox analyses, such as molybdenum enrichment to indicate euxinic deposition, will help to define a link between the sedimentological and ichnological textural features and basin-wide depositional conditions. The data collected from this study will result in the identification of small-scale physio-chemical fluctuations within the basin during deposition of the Canol shales. This will ultimately lead to a deeper understanding of the large-scale geochemical and sequence stratigraphic trends occurring throughout the formation.