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The Silurian-Mississippian time interval in northeastern North America can be subdivided into major interregional, depositional, and erosional episodes, reflecting vertical movements of the North American crustal plate. A detailed analysis of the preserved depositional record indicates the presence of 6 major unconformity-bounded sequences on the eastern craton, 3 in the transitional region of New York and Pennsylvania, and 2 on the Appalachian plate margin of the New England States and the Maritime Provinces. Good biostratigraphic and lithostratigraphic control clearly demonstrates that this decrease in the number of sequences is due to an easterly increasing change in tectonic style reflected by higher rates of subsidence, less uniform erosional fragmentation, and bette preservation.
The interregional pattern of preservation and the predominance of carbonate facies suggest broad epeirogenic movements during Silurian time. Pronounced facies changes and variations in thickness during Early and early Middle Devonian time characterize the transition from epeirogenic to orogenic movements of the Acadian orogeny. Isostatic uplift and foredeep development mark the late Middle and late Devonian. The Mississippian record indicates greatly increased subsidence on the craton and tensional block faulting, with renewed volcanism on the Appalachian plate margin.
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