The Aptian-Albian ironstone of the Rapid Creek formation, Little Fish Creek, NWT: implications for Cretaceous Ocean Anoxic Events and critical mineral deposits

The Aptian-Albian Rapid Creek formation is a phosphatic ironstone located in the northern Yukon and Northwest Territories in the Richardson Mountains. Ironstones are Phanerozoic, Fe-rich, marine chemical sedimentary rocks. Metalliferous sediment accumulation occurred in a region of the Sevier foreland basin called the Blow Trough, a north-south oriented structural depression 50 km wide that connected the Western Interior Seaway to the nascent Arctic Ocean. The focus of this thesis is on the sedimentology and sequence stratigraphy of the Rapid Creek formation along Little Fish Creek, Northwest Territories. The Rapid Creek formation thins from ~1000 m thick at the type section in the Yukon Territory to ~200 m in thickness in the study area. Here, three stacked coarsening-upward cycles are interpreted as parasequences, each recording shallowing through storm wave base. Parasequences are defined by flooding surfaces overlain by laminated, organic-rich mudstone that grades upwards into concretionary, microbial, and hummocky cross-stratified ironstone dominated by siderite and apatite. The thickness of these ironstone tops increases in each parasequence, suggesting increased progradation during early highstand conditions. As in many Paleozoic ironstones, Fe is interpreted to have been supplied via upwelling, which stimulated high surface ocean productivity by tapping nutrient-rich, ferruginous bottom waters. Restricted circulation in the nascent Arctic Ocean and weathering mafic rocks of the High Arctic Large Igneous Province (HALIP) under a greenhouse climate may have been important for producing anoxic seawater enriched in Fe and Mn to the Blow Trough. Such an interpretation implies that the Aptian-Albian Oceanic Anoxic Event (OAE) 1b may have been regional rather than global in extent. Other OAE may also have been more localized than previously thought, controlled by local tectonic, oceanographic, and sedimentologic conditions. Reinterpretation of ironstones like the Rapid Creek formation provides a foundation for developing new exploration models tuned for discovering critical mineral (Fe, Mn, P) deposits in Canada.

Department dc:contributor.department

Geological Sciences and Geological Engineering

Year dc:date.issued

2026

Author dc:creator

• Tessier, Eric Mitchell-Lloyd

Advisor dc:contributor.supervisor

• Peir, Pufahl

• Ironstone
• Upwelling
• Oceanic Anoxic events
• Mesozoic Ironstone
• Mn, P Ironstone

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/36055

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/36055