Lockatong Formation
Encyclopedia
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
.
, silty argillite
, and laminated mudstone
. In New Jersey, the cyclic nature of the formation is noted with hornfels
near diabase
and basalt
flows.
or litoral sediments. The interfingering nature of the sediments with the surrounding Stockton Formation
and Passaic Formation
suggests that these litoral environments shifted as climate or as the dynamic terrane of the area developed. The deposition of calcitic sediments is indicative of a climate with high evaporation rates.
period, being deposited between 237 to 207 (±5) million years ago. It rests unconformably
below many different formations of the Atlantic Coastal Plain
. It interfingers with both the Stockton Formation and Passaic Formation
. There are numerous diabase intrusions and basalt into the Stockton with local contact metamorphic
rocks.
Triassic
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...
Lockatong Formation is a mapped bedrock unit in Pennsylvania
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 is named after the Lockatong Creek
Lockatong Creek
Lockatong Creek is a tributary of the Delaware River in Hunterdon County, New Jersey in the United States.-References:*Gertler, Edward. Garden State Canoeing, Seneca Press, 2002. ISBN 0-9605908-8-9-External links:*...
in Hunterdon County, New Jersey
Hunterdon County, New Jersey
Hunterdon County is a county located in the western section of the U.S. state of New Jersey. As of the 2010 United States Census, the population was 128,349. It is part of the New York Metropolitan Area. Its county seat is Flemington....
.
Description
The Lockatong is defined as a light to dark gray, greenish-gray, and black very fine grained sandstoneSandstone
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,...
, silty 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...
, and laminated 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...
. In New Jersey, the cyclic nature of the formation is noted with hornfels
Hornfels
Hornfels is the group designation for a series of contact metamorphic rocks that have been baked and indurated by the heat of intrusive igneous masses and have been rendered...
near 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...
and basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
flows.
Depositional environment
The Lockatong is often described as lakeLake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
or litoral sediments. The interfingering nature of the sediments with the surrounding 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...
and Passaic Formation
Passaic Formation
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...
suggests that these litoral environments shifted as climate or as the dynamic terrane of the area developed. The deposition of calcitic sediments is indicative of a climate with high evaporation rates.
Age
Relative age dating of the Lockatong places it in the Upper 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, being deposited between 237 to 207 (±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...
below many different formations of the Atlantic Coastal Plain
Atlantic Coastal Plain
The Atlantic coastal plain has both low elevation and low relief, but it is also a relatively flat landform extending from the New York Bight southward to a Georgia/Florida section of the Eastern Continental Divide, which demarcates the plain from the ACF River Basin in the Gulf Coastal Plain to...
. It interfingers with both the Stockton Formation and Passaic Formation
Passaic Formation
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...
. There are numerous diabase intrusions and basalt into the Stockton 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.