Newark Supergroup | |
---|---|
Stratigraphic range: Triassic - Jurassic | |
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 |
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.
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]
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 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]
The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a period of about 120 million years.
The Passaic Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It was previously known as the Brunswick Formation since it was first described in the vicinity of New Brunswick, New Jersey. It is now named for the city of Passaic, New Jersey, which is near where its type section was described by paleontologist Paul E. Olsen.
New Jersey is a very geologically and geographically diverse region in the United States' Middle Atlantic region, offering variety from the Appalachian Mountains and the Highlands in the state's northwest, to the Atlantic Coastal Plain region that encompasses both the Pine Barrens and the Jersey Shore. The state's geological features have impacted the course of settlement, development, commerce and industry over the past four centuries.
The Forest Sandstone is a geological formation in southern Africa, dating to roughly between 200 and 190 million years ago and covering the Hettangian to Sinemurian stages of the Jurassic Period in the Mesozoic Era. As its name suggests, it consists mainly of sandstone.
The Pekin Formation is a Late Triassic (Carnian) geological formation in North Carolina. The Pekin Formation is specific to the Sanford Sub-Basin of the Deep River Basin of North Carolina, although it may be equivalent to the Stockton Formation of Pennsylvania, New Jersey, and New York. The Pekin Formation was deposited in a rift basin along the Atlantic margin of North America during the breakup of the supercontinent Pangaea during the Late Triassic. The most common rocks in the Pekin Formation are red to brown sandstones, representing a terrestrial fluvial (riverine) and floodplain environment in a hot, humid climate. It has yielded both abundant plant and animal fossils, including some of the oldest potential dinosaur footprints in the world and the large predatory crocodylomorph Carnufex carolinensis.
The Triassic Stockton Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It is named after Stockton, New Jersey, where it was first described. It is laterally equivalent to the New Oxford Formation in the Gettysburg Basin of Pennsylvania and Maryland.
The Triassic Lockatong Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It is named after the Lockatong Creek in Hunterdon County, New Jersey.
The Towaco Formation is a mapped bedrock unit in New Jersey. It is named for the unincorporated village of Towaco, which is near the place its type section was described by paleontologist Paul E. Olsen.
The Feltville Formation is a mapped bedrock unit primarily in New Jersey, with one known outlier in Pennsylvania and another one in New York. It is named for the Deserted Village of Feltville in Watchung Reservation, New Jersey, which is near where its type section was described by paleontologist Paul E. Olsen.
The Boonton Formation is a mapped bedrock unit in New Jersey, formerly divided between the Boonton and Whitehall beds of the defunct Brunswick Formation. It is named for the town of Boonton, New Jersey, which is near where its type section was described by paleontologist Paul E. Olsen.
The Stormberg Group is one of the four geological groups that comprises the Karoo Supergroup in South Africa. It is the uppermost geological group representing the final phase of preserved sedimentation of the Karoo Basin. The Stormberg Group rocks are considered to range between Lower Triassic (Olenekian) to Lower Jurassic (Pliensbachian) in age. These estimates are based on means of geological dating including stratigraphic position, lithostratigraphic and biostratigraphic correlations, and palynological analyses.
The Taylorsville Basin is an early Mesozoic rift basin that either outcrops, or is present beneath younger deposits, in Virginia and Maryland. It is part of the chain of rift basins along the eastern part of North America that formed during the break-up of the Pangaea supercontinent. It is filled by a fluvial and lacustrine sedimentary sequence of the Newark Supergroup.
The Doswell Formation is a geologic unit of Upper Triassic age, part of the Newark Supergroup. The Doswell Formation was originally named to refer to a geological sequence which forms the lower part of the sedimentary fill of the Taylorsville Basin in Virginia and Maryland. This sequence was deposited by lakes and rivers in the developing rift basin. However, a 2016 study determined that several geological layers in Pennsylvania as well as the neighboring Richmond Basin of Virginia also qualified as components of the Doswell Formation.
Tanytrachelos is an extinct genus of tanystropheid archosauromorph reptile from the Late Triassic of the eastern United States. It contains a single species, Tanytrachelos ahynis, which is known from several hundred fossil specimens preserved in the Solite Quarry in Cascade, Virginia. Abundant fossils of Tanytrachelos are found in a series of lakebed sediments that were deposited over the course of about 350 thousand years in a lake which existed approximately 230 million years ago. Some fossils are very well-preserved and include the remains of soft tissues. Tanytrachelos is the most likely trackmaker of the ichnogenus Gwyneddichnium.
The Midland Formation is a Mesozoic geological formation in the Culpeper Basin of Virginia. It is a sedimentary unit which formed in a short period of time between the first two basalt flows in the basin: the Hickory Grove and Mount Zion Church basalts. The most common rocks in the formation are dark reddish interbedded sandstones and siltstones, representative of fluvial (stream) environments. Rare but fossiliferous calcareous shale and limestone also occurs, representing recurring lacustrine (lake) conditions. The Midland Formation is considered equivalent to the Shuttle Meadow Formation of the Hartford Basin, the Feltville Formation of the Newark Basin, and the Bendersville Formation of the Gettysburg Basin.
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.
The Meriden Group is a geologic group, part of the Newark Supergroup, in Connecticut. It preserves fossils dating back to the Jurassic period.
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.