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Taconic “Room Problem,” North Adams Gap, and Time of Formation of Basement-Related Nappes in Southwestern New England: Discussion of Papers by Harwood, Norton, and Ratcliffe and Zartman

E-An Zen
E-An Zen
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January 01, 1976

Author's note. This discussion was prepared in 1970 for a specific symposium. Publication of the papers has been delayed, and some of the points discussed in this note are now obsolete. In the context of the publication, however, it seems better not to try to modify it. Surprisingly, some of the possibilities seem to retain current value. February 1975

New data on the stratigraphic and structural relations of the Dalton Formation, the Hoosac Formation, and the Precambrian gneiss units support the idea that the Paleozoic cover across the North Adams gap in northwestern Massachusetts and southern Vermont was emplaced later than the peeling off of the lower Cambrian to Middle Ordovician rocks that constitute the continuous Giddings Brook slice of the Taconic allochthon, thus admitting the restoration of the allochthonous rocks to this zone. Emplacement of the Taconic allochthon was a protracted event that probably lasted into Late Ordovician or even Early Silurian time; it could have overlapped or even been simultaneous with the development of early thrusting and recumbent folding of the Precambrian gneisses on the west front of the Berkshire massif. The movement on the Precambrian rocks was probably directly responsible for the development of the Monument Mountain thrust slices; could it also be the cause of movement of the high Taconic slices? The relative importance of Taconic and Acadian orogenies in this part of the Appalachian orogen may need new assessment.

Having spent most of my mapping efforts in the Appalachian belt in and around the Taconic...

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GSA Memoirs

Contributions to the Stratigraphy of New England

Lincoln R. Page
Lincoln R. Page
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Geological Society of America
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January 01, 1976




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