Paleoecology and sedimentology of late Silurian biogenic structures in the Duoro and Devon Island Formations on western Devon and southwestern Ellesmere Islands, Arctic Canada.

• Main Author: Sweet, Natalie L.
• Format: Thesis
• Language: unknown
• Published: Université d'Ottawa / University of Ottawa 1995
• Subjects: Paleobotany.; Archer; Arctic; Barlow; Barlow Inlet; Canada; Colin Archer Peninsula; Devon Island; Kent Island; North Kent Island; Seal Islands
• Online Access: https://dx.doi.org/10.20381/ruor-8265; http://www.ruor.uottawa.ca/handle/10393/10385

Carbonate buildups of late-Ludlow-Pridoli age occur within an extensive Silurian reef 'belt' in the Canadian Arctic Islands. Two phases of mound development were documented. The buildups include mudmounds in the uppermost Douro Formation on western Devon Island, and skeletal mounds in the Devon Island Formation on southwestern Ellesmere, North Kent, and Seal islands and Colin Archer Peninsula on Devon Island. The mudmounds average 50m in diameter and 15m in height, and are composed predominantly of sparsely fossiliferous lime mudstone containing sponge spicules and micrite fabrics of probable microbial tabulate origin. In a few small ($\sim$3m diameter x 0.5m high) mudmounds, abundant, well-preserved lithistid sponges and distinct microbial fabrics represent an intimate association of encrusting, binding, baffling and sediment-producing constructors. Coral skeletal mounds, averaging 100m in diameter and 35m in height, have stromatactoid-rich mudstone cores and grade upwards from mudstone into fasciculate coral-floatstone and crinoidal wackestone. In contrast, in a skeletal mound core on North Kent Island, a floatstone facies characterized by fasciculate rugose and tabulate corals, and large tabular stromatoporoids, is overlain by a mudstone core facies. Although the skeletal mounds have been completely altered to a fine-grained dolomite, relict fabrics are preserved and suggest a diagenetic sequence similar to that for the mudmounds. The mudmounds grew during a period of substantial platform drowning, apparently related to tectonic movement on the Boothia Uplift. Farther north, growth of the skeletal mounds began on favourable highs of the drowned carbonate ramp, and continued as basinal siliciclastic muds accumulated. The event represented by the hardground and associated physical features can be correlated with related features in buildups farther south where the Douro ramp instead evolved into a carbonate shelf, represented by the Barlow Inlet Formation. (Abstract shortened by UMI.)