See more from this Division: Topical Sessions
See more from this Session: Recent Advances in the Understanding of Adirondack and Southern Grenville Province Tectonics II: In Honor of James McLelland
Abstract:
The external massifs also mark the boundary between the Neoproterozoic-Early Paleozoic shelf sequence to the west and slope-rise sequence to the east. Locally, basal clastics that record the rift-drift transition unconformably overlie basement rocks in the massifs. The massifs probably formed as rifted blocks above low-angle normal faults, and the normal faults were later reactivated as thrusts during Paleozoic collisions. More outboard rifted blocks formed ribbon continents separated from Laurentia by narrow seaways.
The Berkshire massif was emplaced during the Silurian Salinic or Devonian Acadian orogeny as a rigid intracrustal wedge. The leading edge of the massif-wedge is commonly an overturned fold, and it closely followed the boundary between the Taconic thrust sheets and the carbonate shelf rocks. Wedging was favored by the mechanical contrast between the rigid basement gneisses and clastic rocks of the massif compared to mica-rich schists of the Taconic and the carbonate rocks of the shelf sequence.
See more from this Division: Topical Sessions
See more from this Session: Recent Advances in the Understanding of Adirondack and Southern Grenville Province Tectonics II: In Honor of James McLelland