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Geological History

Published:
January 01, 1974

The geological history of the Arisaig region begins with the poorly dated strata of the Browns Mountain Group. Based on fragmentary inarticulate brachiopods, the Browns Mountain has been tentatively dated as Lower Ordovician. The Browns Mountain beds were tightly folded and intruded by a variety of granitic rocks prior to Silurian time. At School Brook Cove, Cape George (Boucot and others, 1959) fossiliferous Middle or Upper Ordovician quartzites occur, which are also intruded by granitic rocks. Unfortunately, the relations of the fossiliferous rocks at School Brook Cove to the adjacent Browns Mountain Group are not established.

BEARS BROOK VOLCANIC GROUP

Dunn Point Formation

The Bears Brook Volcanic Group was formed under predominantly terrestrial conditions, probably during the Upper Ordovician. Subaerial conditions are proved by the complete lateritic soil profiles and the welded tuffs, and it seems likely that the lavas and sediments were emplaced on a basement consisting of the Browns Mountain Group intruded by monzonite stocks. During Dunn Point Formation time, andesites were extruded and flowed southward from a hinterland to the north in a series of sheets and tongues to build up a tableland. The lateritic soil profiles developed on individual andesite flows give information on the time intervals between flows and on the climate of the period. Thickness of laterite profiles is a function of the time interval between flows, and the absence of a laterite on a flow indicates rapid extrusion of successive flows. The climatic factors indicated by the lateritic soils may be summarized as . . .

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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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