Passaic Formation
Encyclopedia
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
.
, siltstone
and mudstone
with a few green and brown shale interbeds; red and dark-gray interbedded argillite
s near the base. In New Jersey, there are conglomerate
and sandstone
beds within the formation.
and alluvial fan
deposits resulting from the rifting of Pangea. The red color is often evidence that the sediments were deposited in arid conditions. Interfingered with the Passaic, the Lockatong Formation
are lake sediments, which were deposited during wetter climatic cycles during the late Triassic. These sediments came from the northwest and contain clasts from Appalachian formations.
period to the early Jurassic
, being deposited between 225 to 190 (±5) million years ago. It rests unconformably
a top many different formations of the Appalachian Piedmont
. It interfingers with the Lockatong Formation and also rests conformably atop the Stockton Formation
. There are numerous diabase
intrusions into the Passaic with local contact metamorphic
rocks.
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
, New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
, and New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
. It was previously known as the Brunswick Formation since it was first described in the vicinity of New Brunswick, New Jersey
New Brunswick, New Jersey
New Brunswick is a city in Middlesex County, New Jersey, USA. It is the county seat and the home of Rutgers University. The city is located on the Northeast Corridor rail line, southwest of Manhattan, on the southern bank of the Raritan River. At the 2010 United States Census, the population of...
. It is now named for the city of Passaic, New Jersey
Passaic, New Jersey
Passaic is a city in Passaic County, New Jersey, United States. As of the 2010 United States Census, the city had a total population of 69,781, maintaining its status as the 15th largest municipality in New Jersey with an increase of 1,920 residents from the 2000 Census population of 67,861...
, which is near where its type section was described by paleontologist Paul E. Olsen
Paul E. Olsen
Paul E. Olsen is an American paleontologist and author and co-author of a large number of technical papers. Growing up as a teenager in Livingston, New Jersey, he was instrumental in Riker Hill Fossil Site being named a National Natural Landmark as a teenager by sending President Richard Nixon a...
.
Description
The Passaic is defined as a reddish-brown shaleShale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
and mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
with a few green and brown shale interbeds; red and dark-gray interbedded argillite
Argillite
An argillite is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts of silt-sized particles. The argillites grade into shale when the fissile layering typical of shale is...
s near the base. In New Jersey, there are conglomerate
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
and sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
beds within the formation.
Depositional Environment
The Passaic is mostly playaSink (geography)
A geographic sink is a depression within an endorheic basin where water collects with no visible outlet. Instead of discharging, the collected water is lost due to evaporation and/or penetration...
and alluvial fan
Alluvial fan
An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial...
deposits resulting from the rifting of Pangea. The red color is often evidence that the sediments were deposited in arid conditions. Interfingered with the Passaic, the Lockatong Formation
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:...
are lake sediments, which were deposited during wetter climatic cycles during the late Triassic. These sediments came from the northwest and contain clasts from Appalachian formations.
Age
Relative age dating of the Passaic places it in the Late TriassicTriassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
period to the early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
, being deposited between 225 to 190 (±5) million years ago. It rests unconformably
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
a top many different formations of the Appalachian Piedmont
Piedmont (United States)
The Piedmont is a plateau region located in the eastern United States between the Atlantic Coastal Plain and the main Appalachian Mountains, stretching from New Jersey in the north to central Alabama in the south. The Piedmont province is a physiographic province of the larger Appalachian division...
. It interfingers with the Lockatong Formation and also rests conformably atop the Stockton Formation
Stockton Formation
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...
. There are numerous diabase
Diabase
Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. In North American usage, the term diabase refers to the fresh rock, whilst elsewhere the term dolerite is used for the fresh rock and diabase refers to altered material...
intrusions into the Passaic with local contact metamorphic
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
rocks.
See also
- Geology of PennsylvaniaGeology of PennsylvaniaThe Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and play an important role in shaping everyday life in the state...
- Geology of New JerseyGeology of New JerseyThe Geology of New Jersey consists of four distinct physiographic provinces. They are: the Atlantic Coastal Plain Province, the Piedmont Province, the Highlands Province, and the Ridge and Valley Province.-Coastal Plain:...