A deep structural profile across the Appalachians of southern Quebec

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Abstract
A 150-km-Iong seismic line was shot from a point on the St. Lawrence River 50 km southwest of Quebec City, southeastward to the U.S. border in 1979. The line crosses the autochthonous domain, the foreland thrust belt, and the alloch-thonous domain of the Humber Zone; it also crosses the Dunnage Zone and overlying rocks of the Connecticut Valley-Gaspé synclinorium. Reflectors on the derived seismic profile have been correlated with surface geology and the logs of four deep wells, and in turn used to construct a deep structural profile across the Appalachians of southern Quebec. The principal conclusions drawn from the profile are: (A) Grenville basement occurs at depth under the Humber Zone, and along with cover rocks, it has been cut by southeast-dipping syndepositional normal faults in the authochthonous domain, the foreland thrust belt, and the northwestern part of the allochthonous domain. Several of the fault blocks were tilted northward. (B) Nappe emplacement took place during Middle Ordovician time. (C) Later Acadian(?) thrust faults in the Notre Dame anticlinorium may have utilized progressively deeper levels of detachment and at depth may involve Grenville basement. (D) Rocks of the Connecticut Valley-Gaspé synclinorium have been thrust over the Dunnage Zone, and along the seismic line they contain no granite plutons at depth.

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