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Raphael Wust, PhD, PGeo, Trican Geological Solutions, presented to Canada’s Energy Geoscientists’ B.A.S.S. Division Trican’s recent work on Montney core analyses and depositional models, and how new evidence amounts to surprising results.
In sedimentary research, whether it is a carbonate or a siliciclastic unit, the ultimate goal is to identify paleodepositional environments, sediment composition and levels of sediment compaction and diagenetic history. The Lower Triassic Montney Formation of the Western Canadian Sedimentary Basin (WCSB) is generally interpreted as a sequence of interbedded siliciclastic sandstones, siltstones and shales deposited in a shallow, clastic ramp setting that deepens to the West and is fed by turbiditic feeder channels. Although modifications of this “general” depositional setting have been proposed, they all infer a siliciclastic source and depositional environment. Sediment transport and deposition occurred along the northwestern margin of the Supercontinent Pangea and only towards the eastern margins, geographically localized coquina units recognized within the middle member are interpreted as inner shelf restricted deposits or parts of turbidite tributaries.
Over the last two years, evidence from British Columbian and Albertan cores analyzed by Trican Geological Solutions shows that the “classic” Montney depositional model needs to be revised. New research of the Middle and Lower Montney shows that the lithology represents former carbonate deposits (bioclastic carbonates to carbonate muds, i.e. packed biomicrite to micrite) that were strongly altered during burial and multiple diagenetic phases. The shallow shelf bottom waters were well-oxygenated and benthic and planktonic shells were abundant (although of low species diversity) which were transported and deposited by occasional strong bottom water currents. The shallow carbonate shelf (20-100 m) extended tens of km away from the eastern shoreline and active fault systems resulted in complex sediment accommodation space across the basin.
This presentation discusses new evidence of the Middle and Lower Montney Members of BC and AB and how the wavy or laminated deposits formed and what processes may have influenced the lithological texture. A new depositional and diagenetic model of a Montney carbonate-dominated shelf margin is also presented. This new model may have significant exploration implications as industry continues to search for new targets within the Montney Formation.
For more information, please contact Trican Geological Solutions.
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