scholarly journals The Cariboo Duplex At the southern Boundary of the Monashee Complex, southern British Columbia

1989 ◽  
Author(s):  
V J Coleman
Keyword(s):  
British Columbia ◽  
Southern Boundary ◽  
Monashee Complex

P–T history and kinematics of the Monashee Décollement near Revelstoke, British Columbia

1989 ◽  
Vol 26 (2) ◽  
pp. 231-243 ◽  
Author(s):  
Larry S. Lane ◽  
Edward D. Ghent ◽  
Mavis Z. Stout ◽  
Richard L. Brown
Keyword(s):  
British Columbia ◽  
Shear Band ◽  
Late Cretaceous ◽  
Hanging Wall ◽  
Multiple Criteria ◽  
Early Eocene ◽  
Kinematic Indicators ◽  
Metamorphic Assemblage ◽  
Monashee Complex

Microstructural and petrofabric analyses of mylonites from the Monashee Décollement demonstrate that the hanging wall was displaced eastward over the footwall. Microstructural kinematic indicators include shear-band foliation, asymmetric strain shadows, and S–C fabrics. Quartz c axes locally exhibit asymmetric fabrics that are consistent with the microstructural evidence for sense of shear. The kinematic evidence is reliable because multiple criteria coexist within individual specimens.Metamorphic assemblages from footwall Monashee Complex pelites at the Revelstoke damsite indicate that the peak metamorphic assemblage was sillimanite–K-feldspar–biotite–almandine–quartz ± plagioclase. Biotite–garnet geothermometry and garnet–plagioclase–sillimanite–quartz geobarometry set broad constraints on metamorphic temperatures but closer constraints on pressures, near 650 °C and 630 MPa.Comparison of these data with Late Cretaceous hornblende cooling ages from the same locality indicates that the metamorphism is at least as old as Late Cretaceous. Complex microstructures relating to repeated mylonitization and annealing render difficult the correlation of metamorphic conditions with mylonitic fabrics. Early mylonitic textures predate the metamorphic equilibration and thus are pre-Late Cretaceous in age. Postmetamorphic mylonites are well preserved, but their ages are poorly constrained. The present interpretation favours a Late Cretaceous to Paleocene age relating to compressional tectonics. However, an Early Eocene age relating to extensional shearing cannot be excluded.

Paleozoic plutonism in southeastern British Columbia

1985 ◽  
Vol 22 (10) ◽  
pp. 1409-1424 ◽  
Author(s):  
Andrew V. Okulitch
Keyword(s):  
British Columbia ◽  
Clear Relationship ◽  
Granitic Gneiss ◽  
Granitoid Pluton ◽  
Quartz Monzonite ◽  
Monashee Complex ◽  
Devonian Age ◽  
Tectonic Slice ◽  
Affected Country ◽  
Made In

U–Pb dates from zircons indicate that plutonic events occurred during the Paleozoic in the Omineca Crystalline Belt in southeastern British Columbia. In the Kootenay Arc, granitoid cobbles in conglomerate of the Carboniferous Milford Group were derived from quartz monzonite and diorite plutons of probable Ordovician age. Near Little Shuswap Lake, gneissic granitoid units have yielded Cambro-Ordovician ages. At least one episode of deformation affected country rocks of unknown age before intrusion. In the Monashee Complex south of Thor–Odin Nappe in South Fosthall Creek, lineated quartz monzonite is of probable Ordovician age. Comparison of fabrics suggests that at least one episode of metamorphism and deformation occurred prior to intrusion. No clear relationship between the cobbles and these plutons can be demonstrated because major faults lie between them, but substantial revision to accepted models of Paleozoic paleogeography of this region will have to be made. In the Clachnaeudainn tectonic slice east of the Monashee Complex, granitic gneiss is of Paleozoic, possibly Siluro-Devonian, age. This pluton appears to be involved in all phases of deformation that affected its country rocks. Near Quesnel Lake, parts of a composite gneissic granitoid pluton appear to be of Devonian or earliest Carboniferous age.

Late Holocene glacial activity at Bromley Glacier, Cambria Icefield, northern British Columbia Coast Mountains, Canada

2013 ◽  
Vol 50 (6) ◽  
pp. 599-606 ◽  
Author(s):  
Kira M. Hoffman ◽  
Dan J. Smith
Keyword(s):  
British Columbia ◽  
Mass Balance ◽  
Late Holocene ◽  
Recent Progress ◽  
Central Coast ◽  
Southern Boundary ◽  
Coast Mountains ◽  
The Holocene ◽  
The Pacific ◽  
Glacial Expansion

Retreating and downwasting glaciers in the British Columbia Coast Mountains are exposing the remains of forests buried during Holocene-age glacial advances. Despite recent progress in discerning the extent of these advances in the Pacific and Kitimat ranges of the southern and central Coast Mountains, comparatively little is known about the character of these advances in the Boundary Ranges of northwestern British Columbia. This research uses dendroglaciologic and radiocarbon analyses to describe late Holocene glacial advances at Bromley Glacier in the Cambria Icefield area. Four intervals of glacial expansion were identified at ca. 2470–2410, 1850, 1450, and 830 14C years BP. Absent were wood remains associated with mid-Holocene episodes of glacier expansion recorded at nearby sites. The late Holocene deposits described at Bromley Glacier are contemporaneous with those found at other glaciers in the southern Boundary Ranges and contribute to a growing understanding of the synchronous response of glaciers in this region to mass balance fluctuations during the Holocene.

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