Revised stratigraphy of the Cookson Group in eastern Maine and southwestern New Brunswick: an alternate view

Authors

  • Allan Ludman Department of Geology, Queens College, City University of New York, Flushing, New York 11367, USA.and Maine Geological Survey, State House Station No. 22, Augusta, Maine 04333, USA.

DOI:

https://doi.org/10.4138/1719

Abstract

Fossil evidence reported by Fyffe and Riva (1990) requires inversion of the stratigraphic succession originally proposed for the St. Croix Terrane (Ludman, 1987). Other suggested revisions, however, are not in accord with structural and sedimentologic data in eastern Maine. Comparison of structural histories indicates that the Pocomoonshine Lake and Digdeguash formations are more appropriately part of the Frederic ton Belt than of the St Croix Terrane as suggested by fyffe and Riva(1990). An alternate view of the stratigraphic and tectonic relationships between the St Croix Terrane and Fredericton Belt includes the following changes: the Pocomoonshine Lake Formation, originally assigned to the St Croix Terrane, is now considered to be the oldest unit of the Fredericton Belt, lying conformably below the Digdeguash Formation; a late Acadian thrust fault is thought to have transported the St Croix Terrane westward over the Fredericton Belt; subsequent high-angle dip-slip and strike-slip faulting have obscured original relationships—these faults now form the boundary between the two terranes in southeastern Maine. RÉSUMÉ Le témoignage apporté par les fossiles qu'ont signaled Fyffe et Riva (1991) nécessite une inversion de la séquence stratigraphique proposée à l'origine pour la Laniere de St Croix (Ludman, 1987). Cependant, les autres révisions, ayant été suggérées sont en contradiction avec les données stiucturales et séclimentologiques en provenance du Maine oriental. La comparaison des antécédents structuraux indique qu'il est plus adéquat d'incorporer les formations de Pocomoonshine Lake et de Digdeguash a la Ceinture de Fredericton qu'à la Lanière de St. Croix comme l'ont suggéré Fyffe et Riva (1991). Une conception de rechange ayant trait aux relations stratigraphiques et tectoniques entre la Laniere de St Croix et la Ceinture de Fredericton englobe les changements suivants: la Formation de Pocomoonshine Lake, rattachée à l'origine à la Lanière de St Croix, est maintenant tenue pour étant la plus vieille unité au sein de la Ceinture de Fredericton, recouverte en concordance par la Formation de Digdeguash; un chevauchement tardi-acadien est envisagé comme ayant transporté la Lanière de St Croix vers l'ouest par-dessus la Ceinture de Fredericton; le jeu subséquent de décrochements et de failles à rejet selon leur pendage, tous fortement inclines, à obscurci les rapports originaux—ces failles constituent maintenant la frontière entre ces deux lanieres dans le sud-est du Maine. [Traduit par le journal]

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Published

1991-03-01

How to Cite

Ludman, A. (1991). Revised stratigraphy of the Cookson Group in eastern Maine and southwestern New Brunswick: an alternate view. Atlantic Geoscience, 27(1). https://doi.org/10.4138/1719

Issue

Vol. 27 No. 1 (1991)

Section

Articles

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