Skehan and Rast (1990) suggested that the Bulgarmarsh terrane may have been thrust northwestward over the Pennsylvanian Narragansett Basin along the Beaverhead shear zone during the Alleghenian orogeny
. However, based on its fossil assemblages, Landing (1996) correlated the Conanicut Group with lower to upper Cambrian stratigraphie units characteristic of Avalonia and discounted the existence of a separate Bulgarmarsh terrane.
Precambrian and Paleozoic collisions are recorded by a granulitic gneiss of Grenvillian age (Cordani et al., 2005, Cardona et al., 2006) and by a Paleozoic gneiss that is related either to the Taconic orogeny or the Alleghenian orogeny
(Cardona et al., 2006; Zuluaga et al., 2009).
3), which was thus expanding oceanwards with time (van Staal et al., 1998; Waldron and van Staal, 2001 and references therein), whereas the Alleghenian orogeny
was due to continent collision during final closure of the Rheic Ocean.
During the Pennsylvanian Period (320-286 Ma), the collision of North America and Africa resulted in the Alleghenian Orogeny
and final assemblage of Pangaea.