Contrasting geology in the Pocologan River and Long Reach areas: implications for the New River belt and correlations in southern New Brunswick and Maine

Authors

  • Susan C. Johnson New Brunswick Department of Natural Resources & Energy, Geological Surveys Branch, P.O. Box 5040, Sussex, NB E4E 5L2, Canada

DOI:

https://doi.org/10.4138/1972

Abstract

The Pocologan River and Long Reach areas are situated in the New River belt, which comprises the westernmost exposures of Neoproterozoic rocks in southern New Brunswick. Previous mapping in the southwestern part of the New River belt indicated that Neoproterozoic and Cambrian rocks in the Pocologan River area are different from coeval strata in the Caledonia belt (Avalon /one sensu stracto) in the Saint John area. Recent mapping in the Long Reach area has shown that there are significant lithological changes across the Robin Hood Lake fault, which bisects the New River belt into northeastern (Long Reach) and southwestern (Pocologan River) segments. Neoproterozoic and Cambrian rocks in the Long Reach area are directly comparable to those in the Caledonia belt, demonstrating that the New River belt is composite. Recent data have also shown that Early Cambrian volcanic activity in the Pocologan River area is broadly contemporaneous with epeirogenic events related to a major sequence boundary in the Avalonian cover sequence. This suggests that the northeastern and southwestern segments of the composite New River belt may have experienced a similar tectonic event, possibly as separate but adjacent continental fragments or as geographically isolated parts of one Gondwanan terrane. The lithological similarity of late Early to (?) Middle Cambrian quartzose sedimentary strata in the Pocologan River area to Middle Cambrian rocks in the St. Croix belt in Maine also supports the suggestion that the St. Croix belt is part of this composite terrane. RÉSUMÉ Les secteurs de la riviére Pocologan et de Long Reach sont situes dans la ceinture de New River, qui englobe les affleurements les plus à I'ouest des roches du Protérozoique supéricur du Sud du Nouveau-Brunswick. Des travaux de cartographic antérieurs dans Ie sud-ouest de la ceinture de New River ont révé;lé que les roches du Protérozoique supeérieur et du Cambrien du secteur de la riviére Pocologan constituaient des exemplaires uniques de stretcs contemporaines de la ceinture de Caledonia (zone d'Avalon au sens strict) dans la région de Saint-Jean. Des travaux de cartographic recents dans le secteur de Long Reach ont révélé des changements lithologiques marqués a travers la faille du lac Robin Hood, qui subdivise la ceinture de New River en deux segments : les segments nord-est (Long Reach) et sud-ouest (riviere Pocologan). Les roches du Protérozoique supérieur et du Cambrien du secteur de Long Reach sont directement comparable? à celles de la ceinture de Caledonia, ce qui démontre que la ceinture de New River constitue unc ceinture composite. Des donées récentes ont également rétvélé que I'activitié volcanique du Cambrien inférieur dans le secteur de la riviére Pocologan a en gros été contemporaine aux phénomenes épirogéniques apparentés à une Iimite de séquence importante dans la séquence de couverture avalonnienne. Cela laisse supposer que les segments nord-est et sud-ouest de la ceinture composite de New River pourraient avoir été soumis a un phénomene tectonique analogue, possiblement en tant que fragments continentaux distincts mais adjacents ou de parties géographiquement isolées d'un terrane du Gondwana. La similarity lithologique des strates seédimentaires quartzeuses de la fin du Cambrien précoce au Cambrien moyen (?) dans le secteur de la riviére Pocologan avec les roches du Cambrien moyen de la ceinture de St. Croix au Maine appuie par ailleurs l’hypothése que la ceinture de St. Croix fail partie de ce terrane composite. Traduit par la rédaction

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Published

2001-03-01

How to Cite

Johnson, S. C. (2001). Contrasting geology in the Pocologan River and Long Reach areas: implications for the New River belt and correlations in southern New Brunswick and Maine. Atlantic Geoscience, 37(1). https://doi.org/10.4138/1972

Issue

Vol. 37 No. 1 (2001)

Section

Articles

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