Keppie et al. (2021) presented a Devonian to Carboniferous oroclinal bending hypothesis and dextral strike-slip translation of a single arc terrane to explain the distribution of Cambrian to Ordovician volcanic rocks in the northern Appalachians. We contend that extant data are incompatible with this hypothesis for reasons documented here.

Keppie et al. (2021) interpret the Middle Ordovician volcanic rocks of the northern Miramichi terrane in New Brunswick as on-strike correlatives of the Popelogan arc situated further west that were bent into their present configuration by ca. 120° post-Silurian rotation of the northern Miramichi terrane.

The geological contrasts between the Popelogan...

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