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. 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 .
12-657: The Culpeper Basin is one of the Newark Supergroup 's Triassic rift basins . It lies east of the Appalachian Mountains and extends from the Madison County — Orange County line in Virginia to Frederick , Maryland . A diverse group of sedimentary rocks including siltstone , sandstone , and conglomerate within the basin were intruded by igneous rocks (primarily diabase ), which caused thermal metamorphism at
24-469: A superb example is the New Jersey Palisades sill. 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. The Appalachian Mountains had already been nearly eroded flat by the end of the period; the uplift and faulting that
36-599: The New Mexico Museum of Natural History and Science . His main areas of study are late Paleozoic , Mesozoic and early Cenozoic vertebrate fossils, stratigraphy , and continental deposits, particularly in the American Southwest. His research has taken him on field trips to northern Mexico, Costa Rica , Nicaragua , Jamaica , Kazakhstan , and Georgia , and he conducted extensive field and museum research in China in
48-528: The 1980s and 1990s. He has written more than 500 scientific contributions (about 25-percent are articles in peer-reviewed journals), three books, and has co-edited 14 books. In 2007, some publications by Lucas and associates at the New Mexico Museum of Natural History and Science came under scrutiny after allegations that information was improperly taken from the unpublished and in-press work of graduate students not on his team. Formal complaints were made to
60-494: The Boyds Sill , named after the town of Boyds . Newark Supergroup The Newark Supergroup consists largely of poorly sorted nonmarine sediments; typical rocks are breccia , conglomerate , arkose sandstone , siltstone , and shale . 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. Some of
72-632: The New Mexico Department of Cultural Affairs regarding publications on a new genus of aetosaur (a type of armored prehistoric reptile from the Triassic ), and a reinterpretation of another aetosaur's armor. In July 2008, the Ethics Committee of the Society of Vertebrate Paleontology concluded that the matter could not be resolved in favor of either side. In 2012, he co-authored a paper describing
84-589: The contact with sedimentary rock. The Culpeper Basin is nearly continuous with the Gettysburg Basin to the north and with the Barboursville Basin to the south. The Groveton Member of the Bull Run Formation is exposed there. The formation has produced disarticulated fish remains including isolated bones and scales. The large body of diabase in central Montgomery County , Maryland, is known as
96-584: 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 . Under this hypothesis, the Supergroup was deposited over the course of 50 million years. Spencer G. Lucas Spencer George Lucas is an American paleontologist and stratigrapher, and curator of paleontology at
108-535: The regional formations proposed by this study are: Basin-specific formations are given below: Minor basins crop out in South Carolina (Crowburg, Wadesboro basins), North Carolina (Ellerbe, Davie County basins), Virginia (Scottsburg, Randolph, Roanoke Creek, Briery Creek, Farmville , Flat Branch, Deep Run, Scottsville, Barboursville basins), Connecticut (Cherry Brook Outlier), Massachusetts (Northfield and Middleton basins), and Nova Scotia (Chedabucto Basin). Until
120-524: The rift basins continued from the late Triassic into the early Jurassic . 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,
132-499: The strata are detailed to the level of varves , with indications of Milankovitch cycles . In preserved lake sediments, Semionotus fossils are especially common. 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. The beds dip to the east, while the faults dip westward. The beds are intruded by numerous dikes and sills , indicative of considerable igneous activity;
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#1732852246293144-560: 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. Coarse sediments were deposited near the eastern mountain front, while progressively finer ones were deposited farther west. Evidence suggests the climate at the time was subtropical and rainy, though divided between wet and dry months. A few organic-rich deposits suggest patchy or intermittent swamps and lakes . Accumulation of Newark sediments within
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