The Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary and volcanic rocks which outcrop intermittently along the east coast of North America. They were deposited in a series of Triassic basins, the Eastern North American rift basins, approximately 220–190 million years ago.^[1][2] The basins are characterized as aborted rifts, with half-graben geometry, developing parallel to the main rift of the Atlantic Ocean which formed as North America began to separate from Africa. Exposures of the Newark Supergroup extend from South Carolina north to Nova Scotia. Related basins are also found underwater in the Bay of Fundy. The group is named for the city of Newark, New Jersey.

Quick Facts Type, Sub-units ...

Newark Supergroup
Stratigraphic range: Triassic - Jurassic
Exposed basins of the Newark Supergroup
Type	Supergroup
Sub-units	see text
Location
Region	East Coast, The Maritime Provinces
Country	United States,  Canada
Extent	Nova Scotia, New Brunswick, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Virginia, North Carolina, and South Carolina
Type section
Named for	Newark, New Jersey

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The Newark Supergroup consists largely of poorly sorted nonmarine sediments; typical rocks are breccia, conglomerate, arkose sandstone, siltstone, and shale.^[3][4] Most of the strata are red beds that feature ripple marks, mud cracks, and even rain drop prints; dinosaur footprints are common, though actual body fossils are very rare.^[4] Some of the strata are detailed to the level of varves, with indications of Milankovitch cycles.^[5] In preserved lake sediments, Semionotus fossils are especially common.^[5]

The Newark sediments are extremely thick (up to 6 kilometers); they were deposited in a series of half-grabens that were themselves faulted into block mountains.^[6] The beds dip to the east, while the faults dip westward.^[6] The beds are intruded by numerous dikes and sills, indicative of considerable igneous activity; a superb example is the New Jersey Palisades sill.^[6]

The Newark Supergroup's lithologies and structure are the classic hallmarks of a rift valley; the fault-blocking illustrates the crustal extension forces in play during the breakup of Pangea during the late Triassic Period.^[3] The Appalachian Mountains had already been nearly eroded flat by the end of the period; the uplift and faulting that was the first part of the rifting provided new sources of sediment for the vast thicknesses deposited in the Newark Supergroup; the igneous intrusions are similarly diagnostic of a rift valley.^[3][6] Coarse sediments were deposited near the eastern mountain front, while progressively finer ones were deposited farther west.^[7]

Evidence suggests the climate at the time was subtropical and rainy, though divided between wet and dry months.^[7] A few organic-rich deposits suggest patchy or intermittent swamps and lakes.^[8]

Accumulation of Newark sediments within the rift basins continued from the late Triassic into the early Jurassic.^[2][3]

The separate basins and sub-basins of the Newark Supergroup have historically been given their own geological formations by local paleontologists. However, a study by Weems, Tanner, and Lucas (2016) proposed that the formations of the Newark Supergroup should be defined on a regional scale due to their geological uniformity over eastern North America. From youngest to oldest, the regional formations proposed by this study are:^[9]

• Longmeadow Sandstone of the Portland Group (Early Jurassic semi-arid fluvial deposits)
• Mount Toby Conglomerate of the Portland Group (Early Jurassic semi-arid alluvial conglomerate)
• Boonton Formation of the Portland Group (Early Jurassic lacustrine deposits)
• Hampden Formation of the Meriden Group (Early Jurassic basalts)
• East Berlin Formation of the Meriden Group (Early Jurassic semi-arid lacustrine and alluvial deposits)
• Holyoke Formation of the Meriden Group (Early Jurassic basalts and rare sediments)
• Shuttle Meadow Formation of the Meriden Group (latest Triassic-earliest Jurassic lacustrine and freshwater limestone deposits)
• Talcott Formation of the Meriden Group (latest Triassic (Rhaetian) basalts and rare sediments)
• Passaic Formation of the Chatham Group (Norian-Rhaetian? semi-arid fluvial and deltaic deposits)
• Lockatong Formation of the Chatham Group (Norian?^[10] Humid lacustrine deposits)
• Stockton Formation of the Chatham Group (Carnian? Humid fluvial and deltaic deposits)
• Doswell Formation of the Chatham Group (Early Carnian? Humid fluvial, lacustrine, and coal deposits)
• Evangeline Formation of the Acadia Group (Ladinian? semi-arid fluvial deposits)^[11]
• Economy Formation of the Acadia Group (Anisian-Ladinian? arid fluvial deposits and aeolian sandstone)^[11]
• Chedabucto Formation of the Acadia Group (stratigraphically uncertain red beds at Chedabucto Bay)
• Honeycomb Point Formation of the Acadia Group (Late Permian? arid alluvial conglomerate and aeolian sandstone)^[12]

Basin-specific formations are given below:

Until the late 1970s, the entire Newark Supergroup was assumed to be Triassic in age. A 1977 study of fossil pollen argued that the sediments actually range from the Ladinian to the Lower Jurassic.^[13] Under this hypothesis, the Supergroup was deposited over the course of 50 million years.^[1]

• Passaic Formation
• Gettysburg Formation
• New Oxford Formation
• List of dinosaur-bearing rock formations