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Book Chapter

Acadian Orogeny

Published:
January 01, 1974

The evidence of major changes associated with the Devonian earth movements in the northern Appalachians may be examined under the following headings: (1) change from marine to nonmarine facies; (2) unconformities; (3) granites; (4) pebbles in younger conglomerates; (5) structural differences in rocks above and below the unconformities.

1. The changes from marine to nonmarine facies in Nova Scotia and the adjacent areas of the northern Appalachians are summarized in Figure 30. These occurred in the Eastport and in the Arisaig belts well before the onset of any widespread folding. The first change to nonmarine conditions occurred toward the end of Ludlow times in the Eastport belt and in the Arisaig belt. But this was temporary; marine conditions were again widespread during the Pridoli and the early part of the lower Gedinnian. Persistent nonmarine environments only appeared in the Eastport and Arisaig belts after the early Gedinnian. The sea, however, persisted in the southeasterly Annapolis Valley belt from the Ludlow through the lower Emsian. There is thus no direct time relation between the marine to nonmarine facies changes and the onset of folding in Devonian times.

2. Unconformities are present above Early Devonian (Siegenian or later) beds in the two northwesterly belts (where nonmarine conditions had prevailed for some time prior to the folding); the Annapolis Valley belt had marine sedimentation continuing until lower Emsian time. After widespread folding throughout the northern Appalachians, the first postorogenic deposit in the region was the Upper Devonian Perry Sandstone, although still earlier (Middle . . .

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GSA Special Papers

Geology of the Arisaig Area, Antigonish County, Nova Scotia

A. J. Boucot
A. J. Boucot
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J. F. Dewey
J. F. Dewey
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D. L. Dineley
D. L. Dineley
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R. Fletcher
R. Fletcher
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W. K. Fyson
W. K. Fyson
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J. G. Griffin
J. G. Griffin
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C. F. Hickox
C. F. Hickox
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W. S. McKerrow
W. S. McKerrow
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A. M. Ziegler
A. M. Ziegler
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Geological Society of America
Volume
139
ISBN print:
9780813721392
Publication date:
January 01, 1974

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