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What does the Newark Group reveal about the timing of Appalachian mountain building?

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Triassic paleogeography — Triassic Period Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Triassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

The Newark Group does not provide information regarding the active timing of Appalachian mountain building; rather, it serves as a post-orogenic indicator. The Newark Group consists of unmetamorphosed sedimentary rocks deposited in fault-bounded basins during the Late Triassic and Early Jurassic.12

Because these sediments remain unmetamorphosed, they demonstrate that their deposition occurred after the primary phase of the Appalachian orogeny, which concluded during the late Paleozoic era. Instead of recording mountain-building events, the Newark Group reveals the subsequent period of crustal extension and rifting that occurred along the Appalachian belt. During this time, the erosion of the already-formed Appalachian Mountains provided the thick clastic sequences that filled these grabens.2