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

Abstract

The Pocologan River and Long Reach areas are situated in the New River belt, which comprises the westermost 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 zone sensu stricto) 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.