Gabbs Formation facts for kids
Quick facts for kids Gabbs FormationStratigraphic range: Norian-Hettangian ~225–199Ma |
|
|---|---|
| Type | Formation |
| Unit of | Volcano Peak Group |
| Sub-units | Nun Mine, Mount Hyatt & Muller Canyon Members |
| Underlies | Sunrise Formation |
| Overlies | Luning Formation |
| Lithology | |
| Primary | Siltstone, limestone |
| Other | Mudstone |
| Location | |
| Coordinates | 38°30′N 118°06′W / 38.5°N 118.1°W |
| Approximate paleocoordinates | 18°06′N 55°42′W / 18.1°N 55.7°W |
| Region | Nevada |
| Country |  United States |
| Type section | |
| Named for | Gabbs Valley Range |
| Named by | Muller & Ferguson |
| Year defined | 1939 |
The Gabbs Formation is a special group of rocks found in Nevada, a state in the United States. Scientists call it a geologic formation. It holds amazing clues about life from long, long ago. These clues are called fossils. The fossils found here date back to the Late Triassic and Early Jurassic periods.
This rock formation is very important because it's one of the few places in the U.S. where you can see the exact point in time when the Triassic Period ended and the Jurassic Period began. Imagine it like a special line in the rock layers that marks a huge change in Earth's history!
For a while, a spot in the Gabbs Formation at New York Canyon was considered to be a "Global Boundary Stratotype Section and Point" (GSSP). This is a fancy name for a globally agreed-upon marker in rocks. It helps scientists around the world agree on the start of a new time period. In this case, it was for the Hettangian stage, which is the very first part of the Jurassic Period. However, another location in Austria was chosen instead in 2010.
Contents
What Fossils Are Found Here?
The Gabbs Formation is a treasure chest of ancient sea creatures. It contains many different kinds of ammonites and bivalves, along with other small animals without backbones.
Ammonites: Ancient Shells
Ammonites were amazing creatures that lived in the ocean. They were a bit like modern-day squid or octopuses, but they lived inside a hard, spiral-shaped shell. These shells are often found as fossils. In 2021, scientists described several new types of ammonites from the Gabbs Formation. These include:
- Arcestes lawsi
- Paracochloceras nunminensis
- Peripleurites gabbensis
- Placites heggi
- Rhacophyllites mulleri
- R. volcanoensis
Bivalves: Clams and Oysters
Bivalves are another type of sea creature found as fossils here. These animals have two shells that are hinged together, like a clam or an oyster. They lived on the seafloor. Finding many different types of bivalves and ammonites helps scientists understand what the ancient ocean was like in Nevada millions of years ago.
What Are the Rocks Made Of?
The Gabbs Formation is mostly made of three types of rock:
- Siltstone: This rock is made from very fine particles, like silt, that settled at the bottom of ancient seas.
- Limestone: This rock often forms from the shells and skeletons of sea creatures that pile up over time.
- Mudstone: This rock is made from hardened mud.
These rocks tell us that the area where Nevada is now was once covered by a shallow, open ocean. This was a perfect home for the ammonites and bivalves whose fossils we find today.
