The southern Coast Mountains, British Columbia: New interpretations from geological, seismic reflection, and gravity data

2013 ◽  
Vol 50 (10) ◽  
pp. 1033-1050 ◽  
Author(s):  
Amanda M.M. Bustin ◽  
Ron M. Clowes ◽  
James W.H. Monger ◽  
J. Murray Journeay
Keyword(s):  
British Columbia ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Gravity Data ◽  
Normal Faults ◽  
Southern Coast ◽  
Seismic Profiles ◽  
Coast Mountains ◽  
Clastic Rocks ◽  
Coast Plutonic Complex

The southern Coast Mountains of British Columbia are characterized by voluminous plutonic and gneissic rocks of mainly Middle Jurassic to Eocene age (the Coast Plutonic Complex), as well as metamorphic rocks, folds, and thrust and reverse faults that mostly diverge eastward and westward from an axis within the present mountains, and by more localized Eocene and younger normal faults. In the southeastern Coast Mountains, mid-Cretaceous and younger plutons intrude Bridge River, Cadwallader, and Methow terranes and overlap Middle Jurassic through Early Cretaceous marine clastic rocks of the Tyaughton–Methow basin. The combination of geological data with new or reanalyzed geophysical data originating from Lithoprobe and related studies enables revised structural interpretations to be made to 20 km depth. Five seismic profiles show very cut-up and chaotic reflectivity that probably represents slices and segments of different deformed and rearranged rock assemblages. Surface geology, seismic interpretations, physical properties, and gravity data are combined in two profiles across the Coast Mountains to generate two new 2-D density models that are interpreted in terms of the geological units. The western part of the southern Coast Mountains consists primarily of Jurassic to mid-Cretaceous plutons to depths of 20 km with slices of Wrangellia (in the west) and Early Cretaceous volcanic and sedimentary rocks (Gambier group) in the upper 10 km. The eastern part, east of the Owl Creek fault, consists of slices of Cadwallader and Bridge River terranes and Tyaughton–Methow basin strata with limited slices of plutonic rocks at depths less than 10 km. Below that, Eocene and Late Cretaceous plutons dominate for another 10 km.

Stratigraphy and tectonic setting of the upper part of the Cadwallader terrane, southwestern British Columbia

1990 ◽  
Vol 27 (5) ◽  
pp. 702-711 ◽  
Author(s):  
Paul J. Umhoefer
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Tectonic Setting ◽  
Source Region ◽  
Upper Triassic ◽  
Magmatic Arc ◽  
Clastic Rocks ◽  
Coast Plutonic Complex ◽  
A Minor ◽  
Depositional Setting

The Upper Triassic to Middle Jurassic Cadwallader terrane lies on the northeastern edge of the Coast Plutonic Complex in southwestern British Columbia. Previous work on the Cadwallader Group, the basal unit of the terrane, suggested it was an Upper Triassic (Carnian to middle Norian) volcanic arc and related clastic rocks. Volcanism ceased in early Norian time. A detailed study of the upper part of the Cadwallader terrane (Tyaughton Group and overlying Last Creek formation) shows that it is a sedimentary sequence deposited on the fringe of the inactive Cadwallader magmatic arc. The Upper Triassic (middle to upper Norian) Tyaughton Group consists of nonmarine to shallow-marine clastic rocks and limestones that show sudden changes in depositional setting. The Lower to Middle Jurassic Last Creek formation, a transgressive sequence of clastic rocks, disconformably overlies the Tyaughton Group. The clastic rocks in the two units were derived from a mixed volcanic and plutonic source region that also included a minor metamorphic component and local lower Norian limestones. The stratigraphy of the upper part of the Cadwallader terrane records long-term thermal subsidence of the basin caused by cooling of the magmatic arc after volcanism ceased in the early Norian. The detailed stratigraphy of the upper Cadwallader terrane supports correlation of the Cadwallader with the Stikine terrane, along which it is currently structurally juxtaposed.

Glacier fluctuations during the past millennium in Garibaldi Provincial Park, southern Coast Mountains, British Columbia

2007 ◽  
Vol 44 (9) ◽  
pp. 1215-1233 ◽  
Author(s):  
Johannes Koch ◽  
John J Clague ◽  
Gerald D Osborn
Keyword(s):  
British Columbia ◽  
Little Ice Age ◽  
Ice Age ◽  
Southern Coast ◽  
Coast Mountains ◽  
The Past ◽  
Glacier Fluctuations ◽  
Garibaldi Provincial Park ◽  
Provincial Park ◽  
Past Millennium

The Little Ice Age glacier history in Garibaldi Provincial Park (southern Coast Mountains, British Columbia) was reconstructed using geomorphic mapping, radiocarbon ages on fossil wood in glacier forefields, dendrochronology, and lichenometry. The Little Ice Age began in the 11th century. Glaciers reached their first maximum of the past millennium in the 12th century. They were only slightly more extensive than today in the 13th century, but advanced at least twice in the 14th and 15th centuries to near their maximum Little Ice Age positions. Glaciers probably fluctuated around these advanced positions from the 15th century to the beginning of the 18th century. They achieved their greatest extent between A.D. 1690 and 1720. Moraines were deposited at positions beyond present-day ice limits throughout the 19th and early 20th centuries. Glacier fluctuations appear to be synchronous throughout Garibaldi Park. This chronology agrees well with similar records from other mountain ranges and with reconstructed Northern Hemisphere temperature series, indicating global forcing of glacier fluctuations in the past millennium. It also corresponds with sunspot minima, indicating that solar irradiance plays an important role in late Holocene climate change.

A debris flow triggered by the breaching of a moraine-dammed lake, Klattasine Creek, British Columbia

1985 ◽  
Vol 22 (10) ◽  
pp. 1492-1502 ◽  
Author(s):  
John J. Clague ◽  
S. G. Evans ◽  
Iain G. Blown
Keyword(s):  
British Columbia ◽  
Debris Flow ◽  
Debris Flows ◽  
Southern Coast ◽  
Coast Mountains ◽  
Debris Avalanches ◽  
Unconsolidated Sediment ◽  
Sudden Release ◽  
Dammed Lake ◽  
Unusual Origin

A very large debris flow of unusual origin occurred in the basin of Klattasine Creek (southern Coast Mountains, British Columbia) between June 1971 and September 1973. The flow was triggered by the sudden release of up to 1.7 × 106 m3 of water from a moraine-dammed lake at the head of a tributary of Klattasine Creek. Water escaping from the lake mobilized large quantities of unconsolidated sediment in the valley below and thus produced a debris flow that travelled in one or, more likely, several surges 8 km downvalley on an average gradient of 10° to the mouth of the stream. Here, the flow deposited a sheet of coarse bouldery debris up to about 20 m thick, which temporarily blocked Homathko River. Slumps, slides, and debris avalanches occurred on the walls of the valley both during and in years following the debris flow. Several secondary debris flows of relatively small size have swept down Klattasine Creek in the 12–14 years since Klattasine Lake drained.

Multi-proxy record of Holocene glacial history of the Spearhead and Fitzsimmons ranges, southern Coast Mountains, British Columbia

2007 ◽  
Vol 26 (3-4) ◽  
pp. 479-493 ◽  
Author(s):  
Gerald Osborn ◽  
Brian Menounos ◽  
Johannes Koch ◽  
John J. Clague ◽  
Vanessa Vallis
Keyword(s):  
British Columbia ◽  
Southern Coast ◽  
Glacial History ◽  
Proxy Record ◽  
Coast Mountains ◽  
History Of

Interdecadal patterns of total sediment yield from a montane catchment, southern Coast Mountains, British Columbia, Canada

Geomorphology ◽  
2010 ◽  
Vol 118 (1-2) ◽  
pp. 207-212 ◽  
Author(s):  
Erik Schiefer ◽  
Marwan A. Hassan ◽  
Brian Menounos ◽  
Channa P. Pelpola ◽  
Olav Slaymaker
Keyword(s):  
British Columbia ◽  
Sediment Yield ◽  
Southern Coast ◽  
Coast Mountains ◽  
Total Sediment

Early Holocene climate at Castle Peak, southern Coast Mountains, British Columbia, Canada

1992 ◽  
Vol 95 (1-2) ◽  
pp. 153-167 ◽  
Author(s):  
John J. Clague ◽  
R.W. Mathewes ◽  
W.M. Buhay ◽  
T.W.D. Edwards
Keyword(s):  
British Columbia ◽  
Early Holocene ◽  
Southern Coast ◽  
Holocene Climate ◽  
Coast Mountains

scholarly journals Pollen evidence of Late Holocene treeline fluctuation from the southern Coast Mountains, British Columbia

2002 ◽  
Vol 51 (1) ◽  
pp. 81-92 ◽  
Author(s):  
Martin Evans
Keyword(s):  
British Columbia ◽  
Organic Matter Content ◽  
Matter Content ◽  
Southern Coast ◽  
Coast Mountains ◽  
Alpine Glacier ◽  
The Core ◽  
Surface Samples ◽  
Summer Temperatures ◽  
Glacier Advance

Abstract Palynological records of Holocene climate change in the southern Coast Mountains identify the Neoglacial period, subsequent to 6 600 BP, as cooler and wetter than the preceding Hypsithermal. However, geomorphic evidence of alpine glacier advance suggests that there were three distinct cooler/wetter periods during the Neoglacial. By careful selection of a sensitive alpine site this study has enabled the recognition of two of these stages in a palynological record of Neoglacial climate. Pollen spectra, conifer needle macrofossils, organic matter content, and magnetic susceptibility were assessed for a continuous sequence of sediment from Blowdown Lake, which has a basal date older than 4 000 BP. Comparison of the Picea/Pinus pollen ratios from the core with modern surface samples suggests that treeline was at least 100 m above its present elevation until 3 400 BP, indicating that summer temperatures were at least 0.7 ° C above the present. Treeline declined to near present levels by around 2 400 BP. Two subsequent periods of lower treeline were identified which appear to correlate approximately with the Tiedemann and Late Neoglacial periods of glacier advance in southwestern British Columbia. Differences between Picea/Pinus and Abies/Pinus ratios from the core are consistent with the autecology of the species. This suggests that the sensitivity of the pollen ratio approach to reconstructing treeline is dependent on the ratios selected.

Geology of the Cadwallader Group and the Intermontane–Insular superterrane boundary, southwestern British Columbia

1987 ◽  
Vol 24 (11) ◽  
pp. 2279-2291 ◽  
Author(s):  
Margaret E. Rusmore
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Tectonic Evolution ◽  
Middle Triassic ◽  
Upper Triassic ◽  
Tectonic Block ◽  
Volcanic Arc ◽  
Arc Volcanism ◽  
Clastic Rocks ◽  
Tectonic Settings

Several lower Mesozoic, fault-bounded units separate the Intermontane and Insular superterranes in southwestern British Columbia. Detailed study of one of these Mesozoic units, the Cadwallader Group, helps clarify the boundary between the superterranes and establish the tectonic evolution of southwestern British Columbia. The Cadwallader Group is the oldest unit in an Upper Triassic through Middle Jurassic volcanic and sedimentary tectono-stratigraphic terrane. Two formations, the Pioneer and the Hurley, compose the Cadwallader Group; the previously recognized Noel Formation is no longer considered valid. The Pioneer Formation contains pillow basalt, flows, and basalt breccia. Siltstone, sandstone, conglomerate, and minor amounts of limestone megabreccia and basalt belonging to the Hurley Formation conformably overlie the Pioneer. The Hurley spans latest Carnian or earliest Norian to middle Norian time. Two episodes of deformation affected the Cadwallader, and a thrust fault separates the group from slightly younger clastic rocks of the Tyaughton Group. Similarities in clastic rocks indicate the Tyaughton was deposited on the Cadwallader; together the units form the Cadwallader terrane. Basalts and clastic rocks in the terrane record deposition in or near a Carnian to earliest Norian volcanic arc. Volcanism waned later in the Norian, but presence of the arc is preserved in the clastic rocks.Oceanic rocks of the Middle Triassic to Middle Jurassic Bridge River terrane became juxtaposed with the Cadwallader terrane in Middle Jurassic time, after which the terranes functioned as a single tectonic block. Contrasting volcanic histories suggest that the Cadwallader terrane was not accreted to the Intermontane superterrane until Middle Jurassic or Early Cretaceous time, although the similar tectonic settings of Stikinia and the Cadwallader terrane allow a common earlier history. The Cadwallader terrane is not part of either the Alexander terrane or Wrangellia, and so the inboard margin of the Insular superterrane must lie west of the Cadwallader terrane.

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