Lithostratigraphy of the Nanaimo Group, Georgia Basin, southwestern British Columbia

England, T.D.J.

doi:10.4095/127484

Cited by 25 publications

(61 citation statements)

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“…The beds bearing the fossil cedar were considered Late Cretaceous in age, based on lithological, floral, and faunal correlations (Bell 1957 More recent studies have allowed a more precise age determination of the fossil bearing beds based on litho-and bio-stratigraphy (i.e., Muller and Jeletzky 1970;Ward 1978;Bickford and Kenyon 1988;Bickford et al 1990;England 1989;Haggart and Ward 1989;Rouse et al 1990). The No.…”

Section: Methodsmentioning

confidence: 99%

An early Chamaecyparis (Cupressaceae) from the Late Cretaceous of Vancouver Island, British Columbia, Canada

McIver¹

1994

Can. J. Bot.

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Fossil remains of a Chamaecyparis-like member of the Cupressaceae occur in the Upper Cretaceous Comox Formation of Vancouver Island, British Columbia. The cedar bore both flattened, opposite-branching foliage of the Cupressinocladus interruptus type, as well as alternate-branching foliage more similar to that of extant Thuja. Seed cones attached to the foliage are minute, about 3.0 mm in diameter, and consist of four cone scales with abaxial, leaflike umbos. Despite their small size, the structure of the cones and their disposition on axes resembles those of extant species of Chamaecyparis. It is apparent that the Comox cedar is closely related to extant Chamaecyparis and appears to represent an early member of the clade. These data challenge the hypothesis that Chamaecyparis evolved from a Cupressus-like ancestor with large, many-scaled seed cones and terete branches. Key words: Cupressaceae, Chamaecyparis, Late Cretaceous, fossil, seed cones, evolution.

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Section: Methodsmentioning

confidence: 99%

An early Chamaecyparis (Cupressaceae) from the Late Cretaceous of Vancouver Island, British Columbia, Canada

McIver¹

1994

Can. J. Bot.

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“…However, there is considerable debate over the details of the structure of the Georgia Basin (Mustard and Rouse, 1994;England and Bustin, 1998). Although major faults have been proposed for the Strait of Georgia area (Muller, 1977), none have been found.…”

Section: Geological Setting and Recent Geophysical Studiesmentioning

confidence: 99%

“…The overall structure of the Georgia Basin indicates moderate deformation along a series of mainly northwesttrending faults and folds (England and Bustin, 1998). Much of the Nanaimo group is characterized by shallow northeastto east-dipping beds (Mustard and Rouse, 1994), which locally may reverse their dip over northwest trending folds.…”

Section: Geological Setting and Recent Geophysical Studiesmentioning

confidence: 99%

Characterization of Active Faulting Beneath the Strait of Georgia, British Columbia

Cassidy¹,

Rogers²,

Waldhauser³

2000

Bulletin of the Seismological Society of America

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Southwestern British Columbia and northwestern Washington State are subject to megathrust earthquakes, deep intraslab events, and earthquakes in the continental crust. Of the three types of earthquakes, the most poorly understood are the crustal events. Despite a high level of seismicity, there is no obvious correlation between the historical crustal earthquakes and the mapped surface faults of the region. On 24 June 1997, a M L ‫ס‬ 4.6 earthquake occurred 3-4 km beneath the Strait of Georgia, 30 km to the west of Vancouver, British Columbia. This well-recorded earthquake was preceded by 11 days by a felt foreshock (M L ‫ס‬ 3.4) and was followed by numerous small aftershocks. This earthquake sequence occurred in one of the few regions of persistent shallow seismic activity in southwestern British Columbia, thus providing an ideal opportunity to attempt to characterize an active near-surface fault. We have computed focal mechanisms and utilized a waveform cross-correlation and joint hypocentral determination routine to obtain accurate relative hypocenters of the mainshock, foreshock, and 53 small aftershocks in an attempt to image the active fault and the extent of rupture associated with this earthquake sequence. Both Pnodal and CMT focal mechanisms show thrust faulting for the mainshock and the foreshock. The relocated hypocenters delineate a north-dipping plane at 2-4 km depth, dipping at 53Њ, in good agreement with the focal mechanism nodal plane dipping to the north at 47Њ. The rupture area is estimated to be a 1.3-km-diameter circular area, comparable to that estimated using a Brune rupture model with the estimated seismic moment of 3.17 ‫ן‬ 10 15 N m and the stress drop of 45 bars. The temporal sequence indicates a downdip migration of the seismicity along the fault plane. The results of this study provide the first unambiguous evidence for the orientation and sense of motion for active faulting in the Georgia Strait area of British Columbia.

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“…In 1998 the Seismic Hazard Investigation in Puget Sound (SHIPS) surveyed the southern Georgia basin, yielding new crustal scale tomography velocity models for this important structure (Ramachandran, 2001;Zelt et al, 2001). Although the geology of the San Juan Islands and Lummi Peninsula have been reported (Vance, 1975(Vance, , 1977Brandon et al, 1988;Garver, 1988a,b;Droost, 1996), as well as that of the Georgia Basin (England and Bustin, 1998), few seismic studies of the Lummi Island and other crustal faults in the southern Georgia basin have been reported (Finkbeiner, 1994;Fisher et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Wide-angle seismic recording from the 2002 Georgia Basin Geohazards Initiative, northwestern Washington and British Columbia

Brocher¹,

Pratt²,

Spence³

et al. 2003

Open-File Report

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This report describes the acquisition and processing of shallow-crustal wide-angle seismicreflection and refraction data obtained during a collaborative study in the Georgia Strait, western Washington and southwestern British Columbia. The study, the 2002 Georgia Strait Geohazards Initiative, was conducted in May 2002 by the Pacific Geoscience Centre, the U.S. Geological Survey, and the University of Victoria. The wide-angle recordings were designed to image shallow crustal faults and Cenozoic sedimentary basins crossing the International Border in southern Georgia basin and to add to existing wide-angle recordings there made during the 1998 SHIPS experiment. We recorded, at wide-angle, 800 km of shallow penetration multichannel seismic-reflection profiles acquired by the Canadian Coast Guard Ship (CCGS) Tully using an air gun with a volume of 1.967 liters (120 cu. in.). Prior to this reflection survey, we deployed 48 Refteks onshore to record the airgun signals at wide offsets. Three components of an oriented, 4.5 Hz seismometer were digitally recorded at all stations. Nearly 160,300 individual air gun shots were recorded along 180 short seismic reflection lines. In this report, we illustrate the wide-angle profiles acquired using the CCGS Tully, describe the land recording of the air gun signals, and summarize the processing of the land recorder data into common-receiver gathers. We also describe the format and content of the archival tapes containing the SEGY-formated, common-receiver gathers for the Reftek data. Data quality is variable but the experiment provided useful data from 42 of the 48 stations deployed. Three-fourths of all stations yielded useful first-arrivals to source-receiver offsets beyond 10 km: the average maximum source-receiver offset for first arrivals was 17 km. Six stations yielded no useful data and useful firstarrivals were limited to offsets less than 10 km at five stations. We separately archived our recordings of 86 local and regional earthquakes ranging in magnitude from 0.2 to 4.3 and 16 teleseisms ranging in magnitude 5.5 to 6.5. CONTENTS

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Lithostratigraphy of the Nanaimo Group, Georgia Basin, southwestern British Columbia

Cited by 25 publications

References 0 publications

An early Chamaecyparis (Cupressaceae) from the Late Cretaceous of Vancouver Island, British Columbia, Canada

An early Chamaecyparis (Cupressaceae) from the Late Cretaceous of Vancouver Island, British Columbia, Canada

Characterization of Active Faulting Beneath the Strait of Georgia, British Columbia

Wide-angle seismic recording from the 2002 Georgia Basin Geohazards Initiative, northwestern Washington and British Columbia

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