Stratigraphic Analysis of Cretaceous Strata Flanking the Southern Nechako Basin: Constraining Basin Architecture and Reservoir Potential (NTS 92N, 92O, 93B)
- Peter Mustard, Simon Fraser University

Accurate assessment of the petroleum potential of the Nechako Basin hinges on a comprehensive understanding of the basin architecture developed within Cretaceous strata, which represent the most prospective targets in the subsurface. Regional geology, showing major Cretaceous units of the Nechako, Methow and Tyaughton basins (modified from a BC Ministry of Energy, Mines and Petroleum Resources, 2002; used with permission). Figure published in Summary of Activities 2007, Geoscience BC Report 2008-1. Modeling the subsurface facies distribution of these Cretaceous strata requires detailed stratigraphic analysis of coeval, laterally adjacent strata exposed along the basin margins.

This three-year project will provide a detailed analysis of the Cretaceous stratigraphy of the northern Methow Basin, including the Lower Cretaceous Jackass Mountain Group (JMG), which is probably the best candidate for a major reservoir system in the subsurface of the Nechako Basin. Additional examination of other early Cretaceous sedimentary units of the south central Nechako Basin, commonly termed Skeena Group or "Skeena Assemblage" will help resolve the confusion in terminology for these early Cretaceous units, which may largely represent northern continuations of Methow Basin deposystems.

The JMG and associated strata include thick (100's m), laterally extensive (10's km) marine sandstone successions that overlie and interfinger with marine mudstones. Previous studies of the JMG and bounding successions have been primarily "first order" stratigraphic assessments commonly associated with government regional mapping projects. This study will significantly expand and supersede earlier studies and emphasize more detailed stratigraphic analysis. Photo courtesy of J.R. Goodin

This investigation will provide comprehensive sedimentologic and stratigraphic analysis of Cretaceous strata in the southern part and along the southern margin of the Nechako Basin, including detailed petrologic analysis (with porosity/permeability estimates), provenance studies (detrital mica and zircon, Nd analysis of fine-grained units, geochemistry of conglomerate clasts), biostratigraphic studies and assessment of hydrocarbon reservoir rock potential. Integration of these data sets will be the basis for a comprehensive model of basin evolution during Early Cretaceous time, which should in turn allow prediction of regional changes in facies associations into the subsurface of the Nechako Basin.

Posters and Presentations
2009: Cretaceous evolution of the Methow-Tyaughton Basin, British Columbia: A sedimentologic, geochemical, and isotopic analysis
- Mineral Exploration Roundup Poster (pdf, 3.23MB)

2008: New studies of the Lower Cretaceous sedimentary strata on the southern margin of Nechako Basin - progress and preliminary observations
- Mineral Exploration Roundup Poster (pdf, 21.0MB)

2008: Stratigraphy, Sedimentology and Hydrocarbon Reservoir Potential of the Lower Cretaceous Jackass Mountain Group, Southern Nechako Basin, Camelsfoot Range, BC - Preliminary Observations
- Mineral Exploration Roundup Poster (pdf, 38.7MB)

2008: Stratigraphy, Sedimentology and Hydrocarbon Reservoir Potential of the Lower Cretaceous Jackass Mountain Group, Chilko Lake Area, British Columbia
- Mineral Exploration Roundup Poster (pdf, 3.60MB)

2007: Stratigraphic Analysis of Cretaceous Strata Flanking the Southern Nechako Basin: Constraining basin Architecture and Reservoir Potential
- Mineral Exploration Roundup Poster (pdf, 33.7MB)

Technical Articles
2011: "The Jackass Mountain Group of south-central British Columbia: depositional setting and evolution of an Early Cretaceous deltaic complex"
- Canadian Journal of Earth Sciences, Volume 48(6) p.930-951

2011: "Paleoenvironmental and chronological constraints on the Mount Tatlow succession, British Columbia: first recognition of radiolarian and foraminiferal faunas in the Intermontane Cretaceous back-arc basins of western Canada"
- Canadian Journal of Earth Sciences, Volume 48(6) p.952-972

2009: "Regional facies patterns in the northern Jackass Mountain Group, northern Methow Basin, southwestern British Columbia"
- Summary of Activities 2008, Paper 2009-1 p.183-192 (pdf, 5.80MB)

2008: "New studies of the Lower Cretaceous Jackass Mountain Group on the southern margin of the Nechako Basin, south-central British Columbia: progress and preliminary observations"
- Summary of Activities 2007, Paper 2008-1 p.135-144 (pdf, 9.42MB)

2007: "Stratigraphic Analysis of Cretaceous Strata Flanking the Southern Nechako Basin (Parts of NTS 092M, O; 093B), British Columbia: Constraining Basin Architecture and Reservoir Potential"
- Geological Fieldwork 2006, Paper 2007-1 p.377-380 (pdf, 6.32MB)

Final Deliverables
M.Sc. Thesis - J. Russell Goodin
Sedimentology and stratigraphy of the Lower Cretaceous Jackass Mountain group, Camelsfoot Range, British Columbia - Simon Fraser University, 2008 - Available digitally through Simon Fraser University (pdf, 20.8MB)

Abstract: The Cretaceous Jackass Mountain Group (JMG), within the Camelsfoot Range of south-central B.C., is a >2 km thick succession of marine and nonmarine volcanic-rich, feldspathic litharenite and lithic arkose sandstone, lesser mudstone, and minor conglomerate, ranging early Aptian to Cenomanian/Turonian age. The JMG was deposited in the Jura-Cretaceous Methow-Tyaughton Basin, a piggyback basin that formed atop the accreting Bridge River, Cadwallader, and Shulaps terranes, between west coast North America and impending Insular Belt terranes. It is likely that most JMG sediment was derived from first cycle weathering of nearby source rocks dominated by a mix of moderately weathered volcanic and plutonic complexes. Three facies associations were identified that essentially represents two-thousand metres of sand-rich submarine fan turbidites, delta front or prodelta deposits, and nonmarine sedimentation. Combined, the facies associations represent an overall regression in the Methow-Tyaughton Basin as accreting terranes eventually closed the basin and amalgamated it onto the continent.

M.Sc. Thesis - Catherine MacLaurin
Sedimentology, stratigraphy, and provenance of the Lower Cretaceous Jackass Mountain Group, Chilko Lake area, British Columbia, Canada - Simon Fraser University, 2008 - Available digitally through Simon Fraser University (pdf, 75.6 MB)

Abstract: The Cretaceous Jackass Mountain Group (JMG) near Chilko Lake in south central British Columbia is an approximately 2 km-thick, shallow-marine succession composed of immature, volcanic-rich sandstone, with subordinate mudstone and conglomerate. Deposition of the JMG occurred within the Methow Basin along the western margin of North America, over the accreted Cadwallader, Bridge River and Methow Terranes. Four facies associations represent sedimentation during Albian to Cenomanian time, and are characterized by nearshore and deltaic deposits that accumulated in close proximity to an active volcanic arc system and older uplifted volcanoplutonic arc rocks. Correlation between disparate Cretaceous sedimentary packages was tested by petrographic, geochemical, and detrital zircon analyses. These analyses indicate that the Chilko Lake and the Camelsfoot Range JMG, now offset across the Yalakom Fault, are correlative; however, a direct correlation to the Taylor Creek Group of the Tyaughton Basin remains tenuous.

 



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