LATE CRETACEOUS EXHUMATION OF UNDERPLATED METASEDIMENTARY ROCKS IN THE NORTH AMERICAN CORDILLERA

2019 ◽  
Author(s):  
William A. Matthews ◽  
◽  
Marie-Pier Boivin ◽  
Kirsten Sauer ◽  
Daniel S. Coutts
1990 ◽  
Vol 27 (5) ◽  
pp. 712-726 ◽  
Author(s):  
Robert J. Scammell ◽  
Richard L. Brown

The Monashee Terrane of southeastern British Columbia is composed of Lower Proterozoic basement gneisses unconformably overlain by cover gneisses. The latter constitute a thick (> 2000 m) and laterally extensive (> 150 km) upper-amphibolite-grade succession of metasedimentary rocks, locally intercalated with minor intrusive and extrusive units. This succession is interpreted as reflecting initial broad, amagmatic subsidence and sedimentation on a cratonic platform (basement gneisses), most likely of North American affinity. Throughout most of the terrane, syndepositional magmatism is first marked by a laterally extensive (> 100 km) stratiform pyroclastic carbonatite, which is part of intermittent (long-lived?) alkaline magmatism. One alkaline body was intruded at ca. 740 ± 36 Ma (U–Pb zircon), suggesting that it may be part of initial Windermere rifting. Post-pyroclastic-carbonatite syndepositional extensional tectonism is further evidenced at the north end of the terrane by interlayered mature and immature siliciclastic sediments, with rapid facies changes, intercalated with ultramafic and mafic sills and flows, plus minor felsic pyroclastic deposits. All of these later deposits lie above stratigraphy correlated with strata hosting a stratiform Pb–Zn deposit with an Early Cambrian galena Pb-isotope age and, therefore, may be correlative with a rift–drift transition recorded in Hamill Group strata to the east. Rift tectonism recorded in cover gneisses may reflect one or more documented rift and rift–drift events recorded in Upper Proterozoic to Lower Cambrian strata of the western North American continental terrace prism.


Geology ◽  
1983 ◽  
Vol 11 (1) ◽  
pp. 11 ◽  
Author(s):  
Maurice Mattauer ◽  
Bernard Collot ◽  
Jean Van den Driessche

2019 ◽  
Vol 146 (726) ◽  
pp. 314-326
Author(s):  
Kerstin Hartung ◽  
Theodore G. Shepherd ◽  
Brian J. Hoskins ◽  
John Methven ◽  
Gunilla Svensson

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