The Passaic Formation is a mapped bedrock unit in

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

, and

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

. It was previously known as the Brunswick Formation since it was first described in the vicinity of

New Brunswick, New Jersey New Brunswick is a city (New Jersey), city in and the county seat of Middlesex County, New Jersey, Middlesex County, in the U.S. state of New Jersey.Passaic, New Jersey Passaic ( or ) is a City (New Jersey), city in Passaic County, New Jersey, Passaic County, in the U.S. state of New Jersey. As of the 2020 United States census, the city was List of municipalities in New Jersey, the state's 16th-most-populous ...

, which is near where its type section was described by paleontologist Paul E. Olsen.

Description

The Passaic is defined as a reddish-brown

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

and

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

with a few green and brown shale interbeds; red and dark-gray interbedded

argillite Argillite () is a fine-grained sedimentary rock composed predominantly of Friability, indurated clay particles. Argillaceous rocks are basically lithified muds and Pelagic sediment, oozes. They contain variable amounts of silt-sized particles. T ...

s near the base. In New Jersey, there are conglomerate and

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

beds within the formation.

Depositional environment

The Passaic is mostly shallow lakes, playa, and alluvial fan deposits resulting from the rifting of

Pangea Pangaea or Pangea ( ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia (continent), Siberia during the Carboniferous period ...

. The red color is often evidence that the sediments were deposited in arid conditions.Faill, R.T., (2004). The Birdsboro Basin. ''Pennsylvania Geology'' V. 34 n. 4. The Passaic Formation overlies the

Lockatong Formation 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. Description The Lockatong is defined as a light to dark gray, greenish-g ...

deep lake sediment cycles, which were deposited during wetter climatic cycles during the Late Triassic. These sediments came from the northwest and contain clasts from Appalachian formations.

Fossils

*'' Clepsysaurus'' *''

Hypsognathus fenneri ''Hypsognathus'' (from , 'height' and , 'jaw') is an extinct genus of procolophonid parareptile from the Late Triassic of New Jersey, Connecticut, and Nova Scotia. ''Hypsognathus'' resembled a moderately sized lizard, with a length of , alth ...

Age

The Passaic is Late Triassic with an astronomically calibrated age of 219 to 201.7 million years ago (Ma) and is about 13,000 ft (~4 km) thick in the basin depocenter. It conformably overlies the

(darker, generally gray shales and mudrocks) and is overlain by the first Watching(Orange Mountain Formation) basalt. The Triassic/Jurassic boundary and correlated by pollen is located in the uppermost part of the formation, ~ 2 precessional cycles (~10–12 m) below the Orange Mountain Basalt. There are numerous

diabase Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-gra ...

intrusions into the Passaic with local

contact metamorphic Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chem ...

rocks.Berg, T.M., et al., (1983). Stratigraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.

Description

Depositional environment

Fossils

Age

References

See also