Abstract

The Emma Lake thrust stack is a duplex structure consisting of basement-cored fold nappes with thrust-through overturned limbs developed in greenschist-facies metamorphic rocks. Geometric relationships between fold nappes and thrust surfaces indicate both regular-sequence and out-of-sequence thrusting occurred during development of the thrust stack. Microstructural analysis shows that regular-sequence thrusts developed under ductile conditions, whereas out-of-sequence thrusts developed in a brittle–ductile field.The structural geometry and metamorphic grade of the Emma Lake thrust stack indicate that it developed under ductile conditions at upper midcrustal levels. The geometry of the Emma Lake thrust stack suggests that structural styles common to higher level fold and thrust belts may be traced into deeper levels of the crust.

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