Newark Supergroup Explained
| Newark Supergroup |
| Type: | Supergroup |
| Age: | Triassic - Jurassic |
| Namedfor: | Newark, New Jersey |
| Region: | East Coast, The Maritime Provinces |
| Country: | , |
| Subunits: | see text |
| Extent: | Nova Scotia, New Brunswick, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Virginia, North Carolina, and South Carolina |
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.
Characteristics
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 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; a superb example is the New Jersey Palisades sill.
Depositional environment
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 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 the rift basins continued from the late Triassic into the early Jurassic.
Basins and formations
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:[3]
Basin-specific formations are given below:
Deep River Basin, Sanford/Durham/Wadesboro Sub-Basins (North Carolina)
Danville/Dan River Basin (North Carolina, Virginia)
- Stoneville Formation (equivalent to the Passaic Formation)
- Cow Branch Formation (equivalent to the Lockatong Formation)
- Dry Fork Formation (Dry Fork Member of the Stockton Formation)
- Walnut Cove Formation (Walnut Cove Member of the Stockton Formation)
- Pine Hall Formation (Pine Hall Member of the Stockton Formation)
- Otterdale sandstone (equivalent to the Stockton Formation)
- "Vinita Beds" (Vinita Member of the Doswell Formation)
- "Coal Measures" (equivalent to the Vinita Member of the Doswell Formation)
- "Barren Beds" (equivalent to the Stagg Creek Member of the Doswell Formation)
- Leedstown Formation (equivalent to the Passaic Formation)
- Port Royal Formation (equivalent to the Lockatong Formation)
- Newfound Formation (equivalent to the Stockton Formation)
- Falling Creek Formation (equivalent to the Vinita Member of the Doswell Formation)
- South Anna Formation (equivalent to the Stagg Creek Member of the Doswell Formation)
- Waterfall Formation (equivalent to the East Berlin Formation)
- Sander Basalt (equivalent to the Deerfield Basalt Member of the Holyoke Formation)
- Turkey Run Formation (Turkey Run Member of the Holyoke Formation)
- Hickory Grove Basalt (Hickory Grove Member of the Holyoke Formation)
- Midland Formation (equivalent to the Shuttle Meadow Formation)
- Mount Zion Church Basalt (equivalent to the Talcott Formation)
- Catharpin Creek Formation (Catharpin Creek Member of the Passaic Formation)
- Bull Run Formation (Groveton/Leesburg, Balls Bluff Members of the Passaic Formation)
- Manassas Formation (Manassas, Rapidan/Reston/Tuscarora Creek Members of the Passaic Formation)
Gettysburg Basin (Maryland, Pennsylvania)
- Bendersville Formation (equivalent to the Shuttle Meadow Formation)
- Aspers Basalt (equivalent to the Talcott Formation)
- Gettysburg Formation (Fairfield, Heidlersburg, Plum Rum, and Hammer Creek Members of the Passaic and Lockatong Formations)
- New Oxford Formation (equivalent to the Stockton Formation)
- Irishtown Beds (Irishtown Member of the Doswell Formation)
Newark Basin (Pennsylvania, New Jersey, New York)
Hartford Basin (Connecticut, Massachusetts)
Pomperaug Basin (Connecticut)
- South Brook Basalt (equivalent to the Hampden Formation)
- White Oaks Formation (equivalent to the East Berlin Formation)
- Orenaug Basalt (equivalent to the Holyoke Formation)
- Cass Formation (equivalent to the Shuttle Meadow Formation)
- East Hill Basalt (equivalent to the Talcott Formation)
- South Britain Arkose (equivalent to the Sugarloaf Member of the Passaic Formation)
Deerfield Basin (Massachusetts)
- Mount Toby Formation
- Turners Falls Sandstone (equivalent to the East Berlin Formation)
- Deerfield Basalt (Deerfield Basalt Member of the Holyoke Formation)
- Fall River Beds (equivalent to the Shuttle Meadow Formation)
- Sugarloaf Arkose (Sugarloaf Member of the Passaic Formation)
Fundy Basin (New Brunswick, Nova Scotia)
Minor basins
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).
Age
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.[7] Under this hypothesis, the Supergroup was deposited over the course of 50 million years.
See also
References
- Letourneau, P. M., Olsen, P. E., The Great Rift Valleys of Pangea in Eastern North America. Volume 1. 2003
- Puffer, J. H., Ragland, P. C., Eastern North America Mesozoic Magmatism, Special Paper - Geological Society of America, vol.268. 1992
Bibliography
- Book: Benton, Michael J. . Michael Benton. 1996 . The Penguin Historical Atlas of the Dinosaurs . registration . London . Penguin Books . 9780140513363 .
- Book: James . Monroe . Reed . Wicander . 1997 . The Changing Earth: Exploring Geology and Evolution . 2nd . Belmont . West Publishing Company .
- Book: Carl . Schuchert . Carl . Dunbar . 1947 . Outlines of Historical Geology . 4th . New York . John Wiley & Sons .
External links
Notes and References
- Book: Paleopalynology. Traverse, Alfred. 1988. Unwin Hyman. 0045610010. 17674795.
- Luttrell . Gwendolyn W. . Stratigraphic nomenclature of the Newark Supergroup of eastern North America . U.S. Geological Survey Bulletin . 1989 . 1572 . 1–136 . 30 June 2018.
- Weems. Robert E.. Tanner. Lawrence H.. Lucas. Spencer G.. 2016. Synthesis and revision of the lithostratigraphic groups and formations in the Upper Permian?–Lower Jurassic Newark Supergroup of eastern North America. Stratigraphy. en. 13. 2.
- Kent. Dennis V.. Olsen. Paul E.. Muttoni. Giovanni. 2017-03-01. Astrochronostratigraphic polarity time scale (APTS) for the Late Triassic and Early Jurassic from continental sediments and correlation with standard marine stages. Earth-Science Reviews. en. 166. 153–180. 10.1016/j.earscirev.2016.12.014. 2017ESRv..166..153K . 0012-8252. 2434/491902. free.
- Sues. Hans-Dieter. Olsen. Paul E.. 2015. Stratigraphic and temporal context and faunal diversity of Permian-Jurassic continental tetrapod assemblages from the Fundy rift basin, eastern Canada. Atlantic Geology. 51. 139–205. 10.4138/atlgeol.2015.006. free.
- Nadon. G. C.. Middleton. G. V.. 1985-08-01. The stratigraphy and sedimentology of the Fundy Group (Triassic) of the St. Martins area, New Brunswick. Canadian Journal of Earth Sciences. 22. 8. 1183–1203. 10.1139/e85-121. 1985CaJES..22.1183N . 0008-4077.
- Book: Palynostratigraphy and age of the Newark supergroup : a thesis in geology. Cornet, Bruce. 1977. 81476152.
