Boonton Formation facts for kids
Quick facts for kids Boonton FormationStratigraphic range: Late Hettangian-Sinemurian ~197–190Ma |
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Exposure of the Boonton Formation along a road cut in Pequannock Township, New Jersey.
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| Type | Geological formation |
| Unit of | Newark Supergroup Meriden Group |
| Underlies | Potomac Formation |
| Overlies | Hook Mountain Basalt |
| Thickness | maximum of over 1,640 feet (500 m) |
| Lithology | |
| Primary | Sandstone, siltstone, mudstone |
| Other | Conglomerate, evaporite |
| Location | |
| Coordinates | 40°54′N 74°24′W / 40.9°N 74.4°W |
| Approximate paleocoordinates | 22°42′N 19°48′W / 22.7°N 19.8°W |
| Region | Newark Basin of Eastern North America Rift Basins |
| Extent | continuous for ~30 miles (48 km) in New Jersey |
| Type section | |
| Named for | Boonton, New Jersey |
| Named by | Paul E. Olsen |
| Year defined | 1980 |
The Boonton Formation is a special layer of rock found in New Jersey. Think of it like a giant history book made of stone! It tells us about what the Earth was like millions of years ago. This rock layer is named after the town of Boonton, New Jersey, where scientists first studied it closely.
Contents
What is the Boonton Formation Made Of?
The Boonton Formation is mostly made of reddish-brown or reddish-purple sandstone. It also has layers of red, gray, purple, and black siltstone and mudstone. Sometimes, these layers can contain calcium carbonate or small, hard lumps called dolomitic concretions.
Scientists have found a famous fossil fish bed in a siltstone layer near the top of the formation. This layer is rich in carbonates. You can also find layers of conglomerate mixed in. These are rocks made of smaller, rounded pebbles, often from older rocks like gneiss and granite.
How Did the Boonton Formation Form?
The Boonton Formation formed a long, long time ago when the supercontinent Pangea was breaking apart. This breaking caused huge cracks in the Earth, forming basins where sediments collected. The Boonton Formation is like the very top part of another rock layer called the Passaic Formation.
The Passaic Formation mostly formed in dry places, like playas (dry lakebeds) and alluvial fans (fan-shaped deposits of sediment). This is why it's mostly red. But the Boonton Formation is different! It has many layers that are not red. This tells us that during the time the Boonton Formation was forming, there were more lakes and wetter periods.
Most rock layers in this area show a pattern of wet and dry periods, like alternating red and gray-black layers. But the lower parts of the Boonton Formation are unique. They have many different colors and textures mixed together without a clear pattern. This suggests the environment was changing a lot!
What Fossils Can You Find?
The Boonton Formation is a treasure chest for fossils! Scientists have found many amazing things here, especially fish fossils.
Fish Fossils
Near the top of the formation, you can find fossils of ancient fish. Some examples include:
- The ray-finned fish Semionotus elegans
- The coelacanth Diplurus longicaudatus
- Other fish like Redfieldius and Ptycholepis
Dinosaur and Reptile Tracks
Besides fish, the Boonton Formation also has fossilized footprints! These tracks tell us about the animals that walked here millions of years ago.
- Scientists have found tracks from plant-eating dinosaurs called ornithischians, including a type called Anomoepus.
- You can also find footprints from other reptiles and dinosaurs, like Batrachopus and the meat-eating dinosaur Grallator.
Plant Fossils
The formation also contains fossils of ancient plants. These include:
- Remains of conifer trees.
- Other plant-related fossils like root structures.
- Tiny fossilized pollen grains.
How Old is the Boonton Formation?
The Boonton Formation sits right on top of another rock layer called the Hook Mountain Basalt. This helps scientists figure out its age. It formed between about 197 and 190 million years ago. This time period is known as the late Hettangian stage and the Sinemurian stage of the Jurassic period. That's even before the famous giant dinosaurs like Tyrannosaurus rex roamed the Earth!
