Boonton Formation
Encyclopedia
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
.
, which is mostly playa
and alluvial fan
deposits resulting from the rifting of Pangea. However, unlike the Passaic Formation, which is primarily red in color due to arid conditions at the time of deposition, the Boonton Formation contains a much more significant portion of non-red layers, indicative of lakes present during wetter periods.
A chief difference between the Boonton Formation and all other formations of the Newark Basin is that the lower part of the formation lacks a cyclic deposition pattern. Typically, the sedimentary formations of the Newark Basin feature recurring periods of wet and dry deposition, resulting in a series of alternating red and gray-black beds. However, the lower beds of the Boonton Formation show a wide variety of color and texture arranged in no particular order.
, the coelacanth
Diplurus longicaudatus
, and others, such as Redfieldius and Ptycholepis
, can be found in the uppermost parts of the formation. In other layers, indeterminate fossil ornithischian tracks have been noted (Anomoepus
is reported), along with additional reptile and dinosaur prints, such as those of Batrachopus, and the theropod Grallator
. Fossil conifer remains, as well as other plant related fossils such as root structures and pollen, are also found in the formation.
stage and Sinemurian
stage of the Jurassic.
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...
, formerly divided between the Boonton and Whitehall beds of the defunct Brunswick Formation. It is named for the town of Boonton, New Jersey
Boonton, New Jersey
Boonton is a town in Morris County, New Jersey that was chartered in 1867. As of the 2010 United States Census, the town population was 8,347. The town was originally called "Boone-Towne" in 1761 in honor of the Colonial Governor Thomas Boone....
, 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 Boonton Formation is composed of reddish-brown to reddish-purple fine grained sandstone, as well as red, gray, purple, and black siltstone and mudstone. Siltstone and mudstone layers can be calcareous and feature dolomitic concretions. A well known fossil fish bed is known to exist in a carbonate rich siltstone near the top of the formation. Additionally, cross-bedded conglomerate layers interfinger with beds of the formation, usually bearing clasts of gneiss and granite.Depositional Environment
The Boonton Formation can be characterized as the uppermost continuation of the Passaic FormationPassaic 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...
, which is mostly playa
Dry lake
Dry lakes are ephemeral lakebeds, or a remnant of an endorheic lake. Such flats consist of fine-grained sediments infused with alkali salts. Dry lakes are also referred to as alkali flats, sabkhas, playas or mud flats...
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. However, unlike the Passaic Formation, which is primarily red in color due to arid conditions at the time of deposition, the Boonton Formation contains a much more significant portion of non-red layers, indicative of lakes present during wetter periods.
A chief difference between the Boonton Formation and all other formations of the Newark Basin is that the lower part of the formation lacks a cyclic deposition pattern. Typically, the sedimentary formations of the Newark Basin feature recurring periods of wet and dry deposition, resulting in a series of alternating red and gray-black beds. However, the lower beds of the Boonton Formation show a wide variety of color and texture arranged in no particular order.
Fossils
Fish fossils, including the ray-finned Semiontus elegansSemionotus
Semionotus is an extinct genus of ray-finned fish found throughout Northern Pangaea during the late Triassic, becoming extinct at the start of the Jurassic.-External links:...
, the coelacanth
Coelacanth
Coelacanths are members of an order of fish that includes the oldest living lineage of Sarcopterygii known to date....
Diplurus longicaudatus
Diplurus
Diplurus is a genus of prehistoric coelacanth fish which lived during the Triassic period....
, and others, such as Redfieldius and Ptycholepis
Ptycholepis
Ptycholepis is an extinct genus of prehistoric bony fish having the head and opercular bones ornamented with ridges of ganoin, minute teeth, and thick scales . -See also:...
, can be found in the uppermost parts of the formation. In other layers, indeterminate fossil ornithischian tracks have been noted (Anomoepus
Anomoepus
Anomoepus gracillimus is the name assigned to fossil footprints first reported from Early Jurassic beds of the Connecticut River Valley, Massachusetts, USA in 1802....
is reported), along with additional reptile and dinosaur prints, such as those of Batrachopus, and the theropod Grallator
Grallator
Grallator is an ichnogenus which covers a common type of small, three-toed print made by a variety of bipedal theropod dinosaurs. Grallator-type footprints have been found in formations dating from the late Triassic through to the early Cretaceous periods...
. Fossil conifer remains, as well as other plant related fossils such as root structures and pollen, are also found in the formation.
Age
The Boonton Formation rests conformably above the Hook Mountain Basalt, placing its deposition sometime between approximately 197 and 190 million years ago during the late HettangianHettangian
The Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
stage and Sinemurian
Sinemurian
In the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
stage of the Jurassic.
See also
- 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:...
- List of dinosaur-bearing rock formations
- List of stratigraphic units with ornithischian tracks
- Indeterminate ornithischian tracks
- List of stratigraphic units with ornithischian tracks