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Early Proterozoic Collisional Orogeny along the Northern Thelon Tectonic Zone, Northwest Territories, Canada: Evidence from the foreland
Author(s) -
Tirrul Rein,
Grotzinger John P.
Publication year - 1990
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/tc009i005p01015
Subject(s) - geology , foreland basin , orogeny , fold (higher order function) , geomorphology , tectonics , shear zone , flysch , passive margin , paleontology , décollement , seismology , rift , mechanical engineering , engineering
The subsidence history of Kilohigok Basin (1.9 Ga), N.W.T., Canada reflects the opening and closing of an ocean basin along the present Thelon Tectonic Zone. The basal sedimentary sequence represents a passive‐margin shelf that faced SE toward the orogen. Following passive‐margin subsidence, tectonic loading occurred resulting in rapid subsidence of the outer shelf margin and simultaneous uplift and erosion of the platform interior; a flexural moat formed subparallel to the Thelon Tectonic Zone. The shelf was subsequently drowned and successively buried by deep‐water flysch, shallow‐marine shelf sediments, and fluvial molasse, forming a foreland basin tapered to the NW. Direct structural evidence for the tectonic load is provided by the leading edge of a thin‐skinned thrust‐fold belt exposed in oblique cross‐section within the SE extremity of the basin. Upright folds at high structural levels can be traced downward to recumbent, tight folds and thrusts near the basement/cover contact documenting increasing shear strain with depth. Overall northwest vergence and about 50% shortening is indicated by fold‐thrust geometry and finite stretching lineations, above a brittle/ductile decollement that roots within the Thelon Tectonic Zone.