Near-surface and crustal-scale images of the Nechako basin, British Columbia, Canada, from magnetotelluric investigations1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Geological Survey of Canada, GSC Contribution No.: 20100129.

2011 ◽  
Vol 48 (6) ◽  
pp. 987-999 ◽  
Author(s):  
Jessica Spratt ◽  
Jim Craven
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Hydrocarbon Exploration ◽  
Near Surface ◽  
Low Resistivity ◽  
South Central ◽  
Pine Beetle ◽  
Exploration Risk ◽  
Microseismic Activity ◽  
Seismic Reflectors

Two-dimensional (2-D) models of audio and broadband magnetotelluric (MT) data collected throughout the southern Nechako basin in south–central British Columbia, Canada, provide electrical resistivity images of the Cretaceous to Oligocene volcanic and sedimentary packages and underlying crustal-scale features. Analysis of distortion effects and structural dimensionality indicate that the MT responses are primarily one-dimensional (1-D) at periods less than 0.1 s. Departures from a 1-D response occur with maximum phase differences occurring between 0.1 and 10 s. The upper crustal resistivity models reveal a low resistivity layer at near surface depths, interpreted as Chilcotin basalts, that blankets portions of the region to depths less than 50 m, but locally thicken up to 200 m. Cretaceous sedimentary units (those showing the highest potential for hydrocarbons) are characterized by moderately low resistivities that are laterally variable. More uniform, lower resistivities appear to be associated with the Eocene volcaniclastic groups, suggesting that the MT method can distinguish between these units and may be useful in targeting areas that are more prospective for hydrocarbon exploration. In general midcrustal resistivity values are high, consistent with values of typical volcanic terranes; however, a low-resistivity zone is identified at 8–10 km depth that correlates closely with the location of seismic reflectors as well as recent microseismic activity. This low-resistivity zone is interpreted as a midcrustal reservoir of magma, the top of which marks the upper limit of fluids migrating from lower crust depths. Additionally, several crustal-scale faults are imaged.

Lithostratigraphic and tectonic framework of Jurassic and Cretaceous Intermontane sedimentary basins of south-central British Columbia1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

2011 ◽  
Vol 48 (6) ◽  
pp. 870-896 ◽  
Author(s):  
Janet Riddell
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Sedimentary Basins ◽  
Hydrocarbon Exploration ◽  
South Central ◽  
Technological Advances ◽  
Exploration Risk ◽  
History Of ◽  
Geophysical Imaging ◽  
Glacial Cover

The south-central Intermontane belt of British Columbia has a complex architecture comprising late Paleozoic to Mesozoic volcanic and plutonic arc magmatic suites, marine and nonmarine clastic basins, high-grade metamorphic complexes, and accretionary rocks. Jurassic and Cretaceous clastic basins within this framework contain stratigraphy with hydrocarbon potential. The geology is complicated by Cretaceous to Eocene deformation, dismemberment, and dislocation. The Eocene to Neogene history of the southern Intermontane belt is dominated by non-arc volcanism, followed by Pleistocene to Recent glaciation. The volcanic and glacial cover makes this a difficult region to explore for resources. Much recent work has involved re-evaluating the challenges that the overlying volcanic cover has historically presented to geophysical imaging of the sedimentary rocks in this region in light of technological advances in geophysical data collection and analysis. This paper summarizes the lithological and stratigraphic framework of the region, with emphasis on description of the sedimentary units that have been the targets of hydrocarbon exploration.

New geoscientific constraints on the hydrocarbon potential of the Nechako–Chilcotin plateau of central British Columbia

2014 ◽  
Vol 51 (4) ◽  
pp. v-ix ◽  
Author(s):  
Andrew J. Calvert ◽  
Graham D.M. Andrews
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Mountain Pine Beetle ◽  
Geological Mapping ◽  
Hydrocarbon Exploration ◽  
Special Issue ◽  
Near Surface ◽  
Mountain Pine ◽  
Geophysical Surveys ◽  
Pine Beetle

Infestation by the mountain pine beetle, Dendroctonus ponderosae, decimated the forests of central British Columbia from 1999 to 2012, severely impacting the forest industry of the Nechako–Chilcotin plateau. In response, all levels of government recognized the value in developing other areas of economic activity, such as hydrocarbon and mineral exploitation, to support local economies. Exploration for resources beneath the Nechako–Chilcotin plateau has historically been constrained by Tertiary volcanic sequences and Quaternary glacial deposits that obscure the underlying geology and limit geophysical imaging. Thus, a coordinated program comprising additional geological mapping, borehole data analysis, and modern geophysical surveys of the area was initiated in 2006, with the objective of better defining the subsurface geology, solving problems of imaging through the complex near-surface, and developing improved regional geological and tectonic models. An initial set of papers arising from this fieldwork, which focused on issues relevant to mineral and hydrocarbon exploration, was published in June 2011 in a Special Issue of the Canadian Journal of Earth Sciences. This Introduction to the second “Mountain Pine Beetle” Special Issue summarizes a set of scientific papers that focus on topics more related to hydrocarbon exploration and the large-scale structure of the crust. The papers deal with the development, thickness, and present distribution of the most prospective Cretaceous sedimentary rocks, as well as characterizing the physical properties of the near-surface volcanic units.

Integrating ice-flow history, geochronology, geology, and geophysics to trace mineralized glacial erratics to their bedrock source: An example from south-central British Columbia1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Earth Sciences Sector Contribution Number: 20100079.

2011 ◽  
Vol 48 (6) ◽  
pp. 1113-1129 ◽  
Author(s):  
A. Plouffe ◽  
R.G. Anderson ◽  
W. Gruenwald ◽  
W.J. Davis ◽  
J.M. Bednarski ◽  
...  
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Bulk Material ◽  
Magnetic Data ◽  
Ice Flow ◽  
South Central ◽  
Bedrock Geology ◽  
Zircon Crystallization ◽  
Pine Beetle ◽  
Exploration Risk

This study demonstrates how ice-flow history, geochronology, geology, and geophysics may be integrated to enhance the effectiveness of boulder tracing in glaciated regions affected by multiple ice-flow events. Mineralized felsic granitoid boulders (erratics) were discovered 18 years ago on a claim block located 10 km northwest of Little Fort, in the Bonaparte Lake map area (NTS 092P), in south-central British Columbia. Although the boulders have yielded significant gold concentrations (up to 4.15 g/t), their bedrock source is not known. The till near the boulders contains up to 1382 gold grains per 15 kg of bulk material with 75% of the grains having pristine morphology, suggesting a short distance of glacial transport. A U–Pb zircon crystallization age of 198.1 ± 0.5 Ma on one mineralized boulder indicates derivation from an Early Jurassic intrusion. Using a vector addition model based on regional ice-flow patterns, the most recent and detailed bedrock geology map, and recently acquired airborne radiometrics and magnetic data, the northeast sector of the Thuya Batholith (195–205 Ma) is interpreted as the most likely bedrock source of the mineralized boulders.

The Jackass Mountain Group of south-central British Columbia: depositional setting and evolution of an Early Cretaceous deltaic complex1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Earth Science Sector (ESS) Contribution 20100280.

2011 ◽  
Vol 48 (6) ◽  
pp. 930-951 ◽  
Author(s):  
Catherine I. MacLaurin ◽  
J. Brian Mahoney ◽  
James W. Haggart ◽  
J. Russell Goodin ◽  
Peter S. Mustard
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Source Rocks ◽  
South Central ◽  
Marine Sedimentation ◽  
Pine Beetle ◽  
Exploration Risk ◽  
Tectonically Active ◽  
History Of ◽  
Depositional Setting

The Lower Cretaceous Jackass Mountain Group of southwestern British Columbia records a complex history of deltaic and proximal marine sedimentation in a tectonically active area of the Canadian Cordillera. Two Jackass Mountain Group successions, exposed in the Camelsfoot Range and Chilko Lake regions and separated by ∼125 km across the northwest–southeast-trending Yalakom fault, provide details of stratigraphy, sedimentology, petrography, and geochemistry of the group. Restoring dextral movement across the Yalakom fault indicates that these locales were adjacent to one another during deposition; data presented herein support this reconstruction. In addition, detailed sedimentological investigations reveal widespread shallow-marine and deltaic features, indicating that deposition occurred predominantly within a large, shallow-water deltaic system. This interpretation is crucial to the understanding of regional facies patterns and for predicting hydrocarbon potential in adjacent subsurface rocks. New porosity, permeability, and thermal maturity data augment information collected from Jackass Mountain Group strata in the subsurface and indicate that some units represent potential hydrocarbon source rocks.

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 Canada1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Geological Survey of Canada Contribution 20100279.

2011 ◽  
Vol 48 (6) ◽  
pp. 952-972
Author(s):  
James W. Haggart ◽  
J. Brian Mahoney ◽  
Michelle Forgette ◽  
Elizabeth S. Carter ◽  
Claudia J. Schröder-Adams ◽  
...  
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Submarine Fan ◽  
Delta Plain ◽  
Pine Beetle ◽  
Subsurface Sediments ◽  
Exploration Risk ◽  
Reducing Environment ◽  
Intermontane Basins ◽  
Back Arc

The Cretaceous succession at Mount Tatlow, British Columbia, is a cornerstone of Cordilleran stratigraphy, preserving a mostly continuous record of upper Lower Cretaceous to lower Upper Cretaceous sedimentary strata. The succession is capped by volcanic strata of the Powell Creek formation. Lithofacies assemblages within the Mount Tatlow succession reflect sedimentation in a deep-water submarine fan system at the base of the section, to overlying submarine-fan and to pro-deltaic deposition, and, finally, to delta-plain sedimentation at the top of the succession. Radiolarian and foraminifer fossils from the lower part of the Mount Tatlow section are the first recovered from the Intermontane basins of British Columbia and indicate a middle Albian to Cenomanian age, most likely Cenomanian. The presence of these fossils indicates that open-marine conditions existed locally in the basin at this time, but the strongly altered and pyritized nature of the fauna suggests that a reducing environment fostered early diagenetic pyritization processes in the subsurface sediments. Detrital zircon populations collected from the succession are in agreement with the paleontological ages.

Density and distribution of advance regeneration in mountain pine beetle killed lodgepole pine stands of the Montane Spruce zone of southern British Columbia

2008 ◽  
Vol 38 (11) ◽  
pp. 2826-2836 ◽  
Author(s):  
Gordon D. Nigh ◽  
Joseph A. Antos ◽  
Roberta Parish
Keyword(s):  
British Columbia ◽  
Spatial Distribution ◽  
Mountain Pine Beetle ◽  
Lodgepole Pine ◽  
Spatial Scales ◽  
South Central ◽  
Advance Regeneration ◽  
Mountain Pine ◽  
Pine Beetle ◽  
Pine Stands

Insect outbreaks, such as the current mountain pine beetle ( Dendroctonus ponderosae Hopkins) outbreak in lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forests in British Columbia, are major disturbances in many forests. After an insect outbreak, the advance regeneration typically forms a new canopy, which may be adequate for timber objectives in some stands. Our purpose was to quantify and then model the abundance and spatial distribution of advance regeneration (trees <10.0 m tall). We sampled understory and overstory trees in 28 lodgepole pine stands in south-central British Columbia at two spatial scales: 0.1 ha plots and 25 m2 subplots. We developed models predicting advance regeneration abundance and spatial distribution. Density of advance regeneration averaged 2689 trees/ha (range 120 to 23 000 trees/ha), most of which were <1 m tall. Although advance regeneration was clumped, 75% of the subplots contained at least one individual. Models indicated negative relationships of advance regeneration abundance to overstory basal area and density. Over half the stands had enough advance regeneration to form new stands of adequate density, indicating that use of advance regeneration is a viable option in this mountain pine beetle outbreak and probably other insect disturbances.

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