The Antlers Formation is a geologic stratum of Early Cretaceous age (late Aptian to early Albian, approximately 120–112 million years ago) that extends from Arkansas through southern Oklahoma into northeastern Texas in the United States. It is a recognized and well-documented geological unit within the Trinity Group.
Lithology and Thickness
The formation is approximately 150 meters (490 feet) thick and consists primarily of silty to sandy mudstone and fine- to coarse-grained sandstone that is poorly to moderately sorted. The sediment is cemented with clay and calcium carbonate. In some locations, the sandstone may be conglomeratic or ferruginous (rich in iron oxides). The unit comprises unconsolidated to semi-consolidated quartz sands and represents fluvial, deltaic, and strandplain depositional environments.
Stratigraphy and Naming
The formation was named by geologist Robert Thomas Hill, with its type locality near Antlers, Pushmataha County, southeastern Oklahoma. It is part of the Trinity Group and lies unconformably over Paleozoic rocks. The Antlers Formation is correlated with the Trinity Group of Texas, which supports its late Aptian–early Albian age assignment.
Paleontology
The Antlers Formation is notable for its fossil content, which includes a diverse vertebrate fauna:
- Dinosaurs: The formation has yielded remains of Acrocanthosaurus atokensis, Deinonychus antirrhopus, Tenontosaurus, Sauroposeidon proteles, and Astrodon. The presence of Deinonychus and Tenontosaurus, which are also known from the Cloverly Formation, supports the age correlation.
- Mammals: Fossil remains include Astroconodon, Atokatheridium boreni, and possible multituberculate and tribosphenidan material.
- Reptiles: Includes crocodyliforms such as Bernissartia, lepidosaurs such as Atokasaurus and Ptilotodon, and turtles including Naomichelys and possible Glyptops.
- Fish: Both cartilaginous fish (e.g., Hybodus, Lissodus) and ray-finned fish (e.g., Gyronchus, possible Palaeobalistum) have been documented.
- Amphibians: Indeterminate frog and possible salamander remains, as well as the albanerpetontid Albanerpeton arthridion.
Hydrogeology
The Antlers Formation functions as an important aquifer in Oklahoma, known as the Antlers Aquifer, which is one of the largest aquifers in the state by storage volume. It supplies groundwater in several counties in southern and southeastern Oklahoma.
References
- Hill, R.T. (1894). "Geology of parts of Texas, Indian Territory and Arkansas adjacent to Red River." Bulletin of the Geological Society of America, 5: 303.
- Weishampel, D.B., et al. (2004). The Dinosauria, 2nd edition.
- U.S. Geological Survey, National Geologic Map Database (Geolex), Antlers Formation entry.
