Distribution of the Chilcotin Group, Taseko Lakes and Bonaparte Lake map areas, British Columbia

Dohaney, Jacqueline; Andrews, Graham; Russell, James K.; Anderson, R G

doi:10.4095/261655

Cited by 3 publications

(9 citation statements)

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“…The economic mineral inventory around this geological unit is significant; however, its presence has led to a mineral exploration deficit compared with its surrounding terrain (Mihalynuk 2007). The thickness and distribution of the group are very poorly known, as much of it is covered by glacial till and marsh Russell 2007, 2008;Dohaney et al 2010).…”

Section: Chilcotin Group Basaltsmentioning

confidence: 99%

“…The 17-1 Ma basalts of the Chilcotin Group are mapped as a 36 500 km 2 cover in central British Columbia (Dohaney et al 2010). The economic mineral inventory around this geological unit is significant; however, its presence has led to a mineral exploration deficit compared with its surrounding terrain (Mihalynuk 2007).…”

Section: Chilcotin Group Basaltsmentioning

confidence: 99%

“…Geophysics is particularly important in this region which has little outcrop. A particular focus for this study is the Miocene Chilcotin Group basalts (Bevier 1983;Mathews 1989), which cover much of the Nechako-Chilcotin plateau and form a serious barrier to mineral exploration Russell 2007, 2008;Mihalynuk 2007;Dohaney et al 2010;Thomas et al 2011). This region is surrounded by mineral showings that raise expectations of mineralization beneath the basaltic cover.…”

Section: British Columbia Geological Frameworkmentioning

confidence: 99%

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The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts^,

Enkin

2014

Can. J. Earth Sci.

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Rock physical properties provide the link between geophysical surveys and their geological interpretation. The British Columbia rock physical properties database, compiled by the Geological Survey of Canada, now comprises 3876 values of density, 930 values of electric resistivity, 12 356 values of magnetic susceptibility, and 2576 values of magnetic remanence and Koenigsberger ratio. The measurements are linked to sample locations, lithologies, and geological formation or unit. Maps, histograms, and biplots are used to demonstrate useful links between lithology and physical properties, and serve as a background for future rock physical properties studies. As expected, density and resistivity are controlled mostly by porosity and mineralogy. Magnetic susceptibility has a bimodal distribution (maxima at 4 × 10 −4 and 2 × 10 −2 SI) controlled by magnetite concentration. Magnetic remanence is shown to be more important than usually considered in magnetic survey analysis, with Koenigsberger ratios greater than unity in 42% of the samples. A case study of the Chilcotin Group basalts is highlighted, as they form a significant barrier to mineral exploration in central British Columbia. These rocks are magnetically distinct from other basalts in British Columbia, distinguished by magnetic susceptibilities having a range of values concentrated around 3 × 10 −3 SI and falling in the valley between the two susceptibility modes. These basalts are also characterized by very high Koenigsberger ratios (96% above unity), probably caused by a preponderance of fine-grained single-domain magnetite. The database provides a wealth of petrophysical properties that can help constrain analysis of several types of geophysical surveys and, in particular, modelling of anomalies in the quest to determine the three-dimensional distribution of rock units. Résumé :Les propriétés physiques des roches constituent le lien entre les levés géophysiques et leur interprétation géologique. La base de données de propriétés physiques des roches de la Colombie-Britannique, compilée par la Commission géologique du Canada, comprend maintenant 3876 valeurs de densité, 930 valeurs de résistivité électrique, 12 356 valeurs de susceptibilité magnétique et 2576 valeurs de rémanence magnétique et de rapport de Koenigsberger. Les mesures sont reliées aux sites d'échantillonnage, aux lithologies et aux formations ou unités géologiques. Des cartes, des histogrammes et des diagrammes de double projection sont utilisés pour démontrer des liens utiles entre la lithologie et les propriétés physiques; ils servent aussi en tant que cadre de référence pour de futures études des propriétés physiques des roches. Tel qu'attendu, la densité et la résistivité sont contrôlées principalement par la porosité et la minéralogie. La susceptibilité magnétique a une distribution bimodale (maximums à 4 × 10 −4 and 2 × 10 −2 SM) contrôlée par la concentration en magnétite. La réma-nence magnétique est démontrée être plus importante que normalement considérée dans les analyses de levés ma...

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Section: Chilcotin Group Basaltsmentioning

confidence: 99%

Section: Chilcotin Group Basaltsmentioning

confidence: 99%

Section: British Columbia Geological Frameworkmentioning

confidence: 99%

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The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts^,

Enkin

2014

Can. J. Earth Sci.

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“…Neogene Chilcotin Group basalts are mapped along the Nazko River valley and to the west of the study area (Fig. 1a), but elsewhere their areal extent is inferred from preexisting compilation maps Massey et al (2005); Dohaney et al (2010). The Nazko Cone (Universal Transverse Mercator (UTM) 449.3 km E, 5864.3 km N) is a PleistoceneHolocene volcano (Souther et al 1987) part of the Anahim volcanic belt and located ϳ10 km southwest of Nazko along Line 06.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…(a) Simplified geological map for the study area and locations of seismic lines and field mapping stations. The geology shown is interpreted from field mapping and observations (Bordet 2014), or based on previous mapping (Mihalynuk et al 2008) or compilations (Massey et al 2005;Dohaney et al 2010). (b) The 2008 Geoscience BC (GBC) Nechako Basin seismic survey comprised seven seismic acquisition lines.…”

Section: Introductionmentioning

confidence: 99%

New geophysical models for subsurface velocity structure in the Nechako–Chilcotin plateau from 2.5-D waveform tomography

2014

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Seismic inversion is applied to generate physical property models (P-wave velocity and numerical attenuation) for four profiles in the Nechako-Chilcotin plateau region of south-central British Columbia, Canada. A newly developed method that combines three-dimensional (3-D) travel-time inversion and 2.5-dimensional (2.5-D) viscoacoustic full-waveform inversion was applied to generate the geophysical models from vibroseis data acquired along the preexisting crooked roads. These models are useful for the characterization of rock types in terms of their positions and thicknesses, which may be used in conjunction with geological ground truth to infer the extent of lithostratigraphic units in the subsurface. The velocity structures also may be used for future reprocessing of the seismic reflection data to derive improved images based on the better near-surface velocity models. The subsurface geology of the Nechako-Chilcotin plateau region is complex, resulting from multiple stages of tectonic compression and extension, contemporaneous with the deposition of sediments and volcanic material. Several basin structures are identified from the joint interpretation of the waveform tomography velocity models and post-stack time migration images. The combination of these results enables the extrapolation and characterization of geological structures to ϳ3 km depth, particularly within the Cenozoic volcanic units that dominate near-surface stratigraphy. Based on the seismic profiles, a fence-diagram geological interpretation that extends to ϳ3 km depth illustrates the complex structure of the Jurassic to Neogene stratigraphic sequence.Résumé : Des modèles de propriétés physiques (vitesse des ondes P et atténuation numérique) sont générés par inversion sismique le long de quatre profiles dans la région du plateau de Nechako-Chilcotin au sud-est de la Colombie Britannique. Une méthode récemment développée combine l'inversion tridimensionnelle (3-D) des temps de trajet et une inversion 2.5-dimensionnelle (2.5-D) des formes d'ondes viscoacoustiques. Cette méthode est utilisée pour générer les modèles géophysiques à partir de données sismiques acquises à partir d'une source vibroseis le long de routes curvilignes. De tels modèles sont utiles afin de caractériser la position et l'épaisseur des successions rocheuses; ainsi, combinés à des données géologiques de surfaces, ces modèles permettent de déduire l'étendue des unités lithostratigraphiques en sous-surface. Les structures imagées par les modèles de vitesse peuvent aussi être utilisées pour le retraitement de données de sismique réflexion: elles permettent d'obtenir des profils améliorés fondés sur des meilleurs modèles de vitesse en proche surface. La géologie du plateau de Nechako-Chilcotin est complexe, et résulte d'évènements tectoniques successifs de compression et extension durant le dépôt de matériel sédimen-taire et volcanique. Plusieurs bassins sont identifiés à partir de l'interprétation conjointe de modèles tomographiques et d'images de migration en temps. La combinaiso...

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Refining the pattern and style of Cordilleran Ice Sheet retreat: palaeogeography, evolution and implications of lateglacial ice‐dammed lake systems on the southern Fraser Plateau, British Columbia, Canada

Perkins

Brennand

2014

Boreas

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Decay of the last Cordilleran Ice Sheet (CIS) near its geographical centre has been conceptualized as being dominated by passive downwasting (stagnation), in part because of the lack of large recessional moraines. Yet, multiple lines of evidence, including reconstructions of glacio‐isostatic rebound from palaeoglacial lake shoreline deformation suggest a sloping ice surface and a more systematic pattern of ice‐margin retreat. Here we reconstructed ice‐marginal lake evolution across the subdued topography of the southern Fraser Plateau in order to elucidate the pattern and style of lateglacial CIS decay. Lake stage extent was reconstructed using primary and secondary palaeo‐water‐plane indicators: deltas, spillways, ice‐marginal channels, subaqueous fans and lake‐bottom sediments identified from aerial photograph and digital elevation model interpretation combined with field observations of geomorphology and sedimentology, and ground‐penetrating radar surveys. Ice‐contact indicators, such as ice‐marginal channels, and grounding‐line moraines were used to refine and constrain ice‐margin positions. The results show that ice‐dammed lakes were extensive (average 27 km2; max. 116 km2) and relatively shallow (average 18 m). Within basins successive lake stages appear to have evolved by expansion, decanting or drainage (glacial lake outburst flood, outburst flood or lake maintenance) from southeast to northwest, implicating a systematic northwestward retreating ice margin (rather than chaotic stagnation) back toward the Coast Mountains, similar in style and pattern to that proposed for the Fennoscandian Ice Sheet. This pattern is confirmed by cross‐cutting drainage networks between lake basins and is in agreement with numerical models of North American ice‐sheet retreat and recent hypotheses on lateglacial CIS reorganization during decay. Reconstructed lake systems are dynamic and transitory and probably had significant effects on the dynamics of ice‐marginal retreat, the importance of which is currently being recognized in the modern context of the Greenland Ice Sheet, where >35% of meltwater streams from land‐terminating portions of the ice sheet end in ice‐contact lakes.

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Distribution of the Chilcotin Group, Taseko Lakes and Bonaparte Lake map areas, British Columbia

Cited by 3 publications

References 0 publications

The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts^,

The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts^,

New geophysical models for subsurface velocity structure in the Nechako–Chilcotin plateau from 2.5-D waveform tomography

Refining the pattern and style of Cordilleran Ice Sheet retreat: palaeogeography, evolution and implications of lateglacial ice‐dammed lake systems on the southern Fraser Plateau, British Columbia, Canada

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Distribution of the Chilcotin Group, Taseko Lakes and Bonaparte Lake map areas, British Columbia

Cited by 3 publications

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The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts,

The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts,

New geophysical models for subsurface velocity structure in the Nechako–Chilcotin plateau from 2.5-D waveform tomography

Refining the pattern and style of Cordilleran Ice Sheet retreat: palaeogeography, evolution and implications of lateglacial ice‐dammed lake systems on the southern Fraser Plateau, British Columbia, Canada

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The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts^,

The Rock Physical Property Database of British Columbia, and the distinct petrophysical signature of the Chilcotin basalts^,