Basin Analysis Studies in the Bowser Basin, Northern British Columbia (NTS 93L, 103P, 104A, 104B, 104G, 104H)
- John Waldron, University of Alberta

The Bowser Basin underlies approximately 50,000 km2 of north-central British Columbia and is considered a frontier hydrocarbon basin. Bowser Basin strata of the Middle Jurassic to mid-Cretaceous Bowser Lake Group overlie volcanic and clastic rocks of the Early to early Middle Jurassic Upper Hazelton Group (Spatsizi Formation). Bowser strata were deposited in a wide range of clastic sedimentary environments, from deep distal marine through slope, shelf, deltaic, fluvial, and lacustrine. Bowser Basin Project AreaThey contain minor carbonates which could potentially be source rocks, and a huge volume of dark grey mudstone, siltstone and shale which are potential source rocks. In addition, fine grained sediments of the Spatsizi formation contain elevated total organic carbon (TOC) and are excellent potential source rocks. The Bowser lake group was deformed by folds and thrust faults to result in the Skeena Fold Belt.

This project will involve field and laboratory investigations by the principle proponent and a graduate student. Fieldwork will investigate selected, stratigraphically intact successions through the basal parts of the Bowser succession. Follow-up laboratory work will include petrographic and geochemical investigations of samples from sedimentary successions. Macrofossils will be collected to refine the stratigraphy, and microfossils, particularly Radiolaria, will be dated with the assistance of appropriate specialists. In addition, to further constrain the subsidence rate of the basin, a program of U-Pb dating of volcaniclastic zircons will be undertaken with the assistance of the staff of the Radiogenic Isotope Facility at the University of Alberta.

The project will aim at preparing sedimentation-rate curves for the basin fill, appropriate to several regions within the basin, which will then be combined with water-depth estimates to produce subsidence curves for the basin. This effort will be facilitated by the good paleontological control and rapid sedimentation rates already documented for the basin. In addition, large portions of the basin fill were deposited in shallow marine or coastal/deltaic environments, allowing us to obtain good constraints on water depth. These curves will help to distinguish between competing models for the origin of the basin (foreland basin, strike-slip basin, rift basin) which have important consequences for petroleum prospectivity.

Posters and Presentations
2009: Jurassic sedimentation Patterns and Reservoir Distribution in a Siliciclastic Tectonically-Active Slope Environment, Northwestern British Columbia (NTS 104B/01)
- Mineral Exploration Roundup Poster (pdf, 3.22MB)

2008: Ridge Section revisited: New insights for the evolution of the Bowser Basin, Northwestern British Columbia
- Mineral Exploration Roundup Poster (pdf, 2.92MB)

Technical Articles
2009: "Sedimentation patterns and reservoir distribution in a siliciclastic, tectonically active slope environment, Bowser Basin, northwestern British Columbia"
- Summary of Activities 2008, Report 2009-1 p.193-200 (pdf, 9.64MB)

2008: "Ashman Ridge section revisited: new insights for the evolution of the Bowser Basin, northwestern British Columbia"
- Summary of Activities 2007, Report 2008-1 p.121-128 (pdf, 5.49MB)
Final Deliverables
Ph.D. Thesis - J-F. Gagnon
Stratigraphic and tectonic evolution of the Jurassic Hazelton trough---Bowser basin, northwest British Columbia, Canada - University of Alberta, 2010 - Available digitally through the University of Alberta (pdf, 57 MB)

Abstract: The Hazelton trough--Bowser basin is a large sedimentary basin that developed on volcanic arc rocks of the Stikine terrane in northern British Columbia, Canada. Its fill mostly consists of the Lower to Middle Jurassic Hazelton Group and the Middle Jurassic to Lower Cretaceous Bowser Lake Group. Regional correlations indicate that the Hazelton Group can be divided in two distinct lithostratigraphic intervals separated in most places by an unconformity. The lower Hazelton Group (LHG) is dominated by arc-related volcanic rocks, whereas the upper Hazelton Group (UHG) contains mainly fine-grained clastic rocks and lesser bimodal rift-related volcanic rocks. Lowermost coarse-grained strata of the UHG, including the bioturbated and fossiliferous units of the Smithers Formation and the Spatisizi River Formation, record a transgressive trend consistent with thermal subsidence and relative sea-level rise. Transgression of the Stikine arc culminated with the establishment of deep-water conditions in the Late Toarcian-Early Aalenian, and deposition of the Quock Formation. Interbedded siliceous mudstone and rusty-weathered tuff of the Quock Formation are correlated throughout most of the basin, except in the Iskut River area on the northwestern margin of the basin, where contemporaneous strata of the Iskut River Formation are dominated by rift-related volcanic rocks and conglomerates. Inception of rifting in the Iskut River area constitutes an independent extensional event on Stikinia, and could be related to reorganization of tectonic plates during a protracted period of terrane accretion in the Middle Jurassic. Obduction of the Cache Creek terrane over Stikinia in early Middle Jurassic provided a new source of sediment, which led to accumulation of the Bowser Lake Group. The second pulse of subsidence observed at Todagin Mountain can be explained by sediment loading of the accommodation previously generated during extension of the Hazelton trough in Early Jurassic time.

 


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