Newark Supergroup

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Newark Supergroup
Stratigraphic range: Triassic - Jurassic
Outcrops of Newark Supergroup Lutrell (1989) USGS Bulletin 1572.png
Exposed basins of the Newark Supergroup
TypeSupergroup
Sub-unitssee text
Location
Region East Coast, The Maritime Provinces
CountryFlag of the United States.svg  United States, Flag of Canada (Pantone).svg  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

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.

Contents

Characteristics

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]

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. [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]

Late Triassic Balls Bluff siltstone of the Bull Run Formation in Manassas, Virginia Balls Bluff Siltstone with Diabase Intrusion (4802113326).jpg
Late Triassic Balls Bluff siltstone of the Bull Run Formation in Manassas, Virginia
Late Triassic New Oxford Conglomerate in York County, Pennsylvania UpperTriassicYorkCountyPA.jpg
Late Triassic New Oxford Conglomerate in York County, Pennsylvania
Late Triassic Gettysburg Formation in York County, Pennsylvania Gettysburg Formation outcrop.jpg
Late Triassic Gettysburg Formation in York County, Pennsylvania
Early Jurassic Preakness Basalt, New Jersey UpperFallsHMPP.jpg
Early Jurassic Preakness Basalt, New Jersey
Feltville Formation in New Jersey 2ndWatchungMountain FeltvilleFormation.jpg
Feltville Formation in New Jersey
Early Jurassic Hook Mountain Basalt in New Jersey HookMountainBasalt.jpg
Early Jurassic Hook Mountain Basalt in New Jersey
Late Triassic Blomidon Formation, Nova Scotia Minor normal faults.JPG
Late Triassic Blomidon Formation, Nova Scotia
Skull diagram of Carnufex carolinensis, a basal crocodylomorph from the Pekin Formation of North Carolina Skeletal reconstruction of Carnufex cropped.png
Skull diagram of Carnufex carolinensis , a basal crocodylomorph from the Pekin Formation of North Carolina
Tanytrachelos ahynis, a tanystropheid reptile from the Cow Branch Formation on the Virginia-North Carolina border Tanytrachelos specimen VMNH.jpg
Tanytrachelos ahynis , a tanystropheid reptile from the Cow Branch Formation on the Virginia-North Carolina border
Early Jurassic Eubrontes footprints from the East Berlin Formation at Dinosaur State Park in Rocky Hill, Connecticut Dinosaur State Park (Rocky Hill, CT) - prints.JPG
Early Jurassic Eubrontes footprints from the East Berlin Formation at Dinosaur State Park in Rocky Hill, Connecticut

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: [9]

Basin-specific formations are given below:

Deep River Basin, Sanford/Durham/Wadesboro Sub-Basins (North Carolina)

Danville/Dan River Basin (North Carolina, Virginia)

Richmond Basin (Virginia)

Taylorsville Basin (Virginia)

Culpeper Basin (Virginia, Maryland)

Gettysburg Basin (Maryland, Pennsylvania)

Newark Basin (Pennsylvania, New Jersey, New York)

Hartford Basin (Connecticut, Massachusetts)

Pomperaug Basin (Connecticut)

Deerfield Basin (Massachusetts)

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. [13] Under this hypothesis, the Supergroup was deposited over the course of 50 million years. [1]

See also

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<span class="mw-page-title-main">Passaic Formation</span>

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<span class="mw-page-title-main">Pekin Formation</span>

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<span class="mw-page-title-main">Feltville Formation</span>

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<span class="mw-page-title-main">Boonton Formation</span>

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The Cumnock Formation is a Late Triassic-age geologic formation in North Carolina. It is found in the Sanford sub-basin of the Deep River Basin, the southernmost of the large Mesozoic basins forming the Newark Supergroup. It is the middle unit of the Chatham Group, overlying the Pekin Formation and underlying the Sanford Formation. Both of these encompassing formations are primarily red sandstone. The Cumnock Formation, on the other hand, represents a sequence of darker lacustrine (lake) or paludal (swampy/marshy) sediments deposited in a tropical climate. These primarily include shales and coal, with some thin layers of coarser sediment such as siltstone and sandstone.

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<span class="mw-page-title-main">Geology of New York (state)</span> Overview of the geology of the U.S. state of New York

The geology of the State of New York is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.

The Sanford Formation is a Late Triassic (Norian)-age geologic formation in North Carolina. It is mainly found in the Sanford sub-basin of the Deep River Basin, the southernmost of the large Mesozoic basins forming the Newark Supergroup. It is the highest unit of the Chatham Group, overlying the dark lake and swamp sediments of the Cumnock Formation. The Sanford Formation is composed primarily of coarse red sediments such as conglomerates, sandstones, and mudstones. The conglomerate layers contain pebbles of schist and slate, with the occasional large boulders of granite.

The Catharpin Creek Formation is a Late Triassic geologic formation in Maryland and Virginia. It is found along the western edge of the Culpeper Basin, one of the largest sedimentary basins in the Newark Supergroup. Compared to the underlying Bull Run Formation, the Catharpin Creek Formation is dominated by much coarser sedimentary rocks such as sandstone and conglomerate. The base of the formation is reddish arkosic sandstone, which grades into drabber thin-bedded siltstone and shale in cyclical sequences.

References

  1. 1 2 Traverse, Alfred (1988). Paleopalynology. Unwin Hyman. ISBN   0045610010. OCLC   17674795.
  2. 1 2 Luttrell, Gwendolyn W. (1989). "Stratigraphic nomenclature of the Newark Supergroup of eastern North America" (PDF). U.S. Geological Survey Bulletin. 1572: 1–136. Retrieved 30 June 2018.
  3. 1 2 3 4 Monroe & Wicander (1997) , p. 602
  4. 1 2 Schuchert & Dunbar (1947) , p. 108
  5. 1 2 Benton (1996) , pp. 88–89
  6. 1 2 3 4 Monroe & Wicander (1997) , p. 605
  7. 1 2 Schuchert & Dunbar (1947) , p. 109
  8. Schuchert & Dunbar (1947) , pp. 108–109
  9. 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. 13 (2).
  10. 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. 166: 153–180. Bibcode:2017ESRv..166..153K. doi:10.1016/j.earscirev.2016.12.014. hdl: 2434/491902 . ISSN   0012-8252.
  11. 1 2 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. doi: 10.4138/atlgeol.2015.006 .
  12. 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. Bibcode:1985CaJES..22.1183N. doi:10.1139/e85-121. ISSN   0008-4077.
  13. Cornet, Bruce (1977). Palynostratigraphy and age of the Newark supergroup : a thesis in geology. OCLC   81476152.

Bibliography