Office of the State Geologist

03/05/2026

STANDING ROCK

Standing Rock is a near vertical 4-foot-thick novaculite bed exposed along Board Camp Creek in Polk County, Arkansas. The Devonian to Early Mississippian Arkansas Novaculite, a very durable rock, crops out from Little Rock westward into Oklahoma and helps define the core area of the Benton Uplift in the Ouachita Mountains. Native Americans used novaculite for many tools, commonly for arrowheads and spear points, and traded from New York to New Mexico....

Standing Rock is a near vertical 4-foot-thick novaculite bed exposed along Board Camp Creek in Polk County, Arkansas. The Devonian to Early Mississippian Arkansas Novaculite, a very durable rock, c…

02/24/2026

https://now.humboldt.edu/news/how-ancient-seafloor-turned-arkansas-sharkansas-shark-fossil-hotspot

Most shark fossils are just teeth—their cartilage skeletons usually decay long before they can fossilize.

01/09/2026

Filiform Pyrite on Poker Chip Calcite

This beautiful sample was recently collected from Pulaski County and donated because of the rare crystal shapes of the minerals. This cavity, or vug, was found in an igneous d**e in the Jackfork Formation. The photos below are magnified to show the crystal shapes. Notice the shape of the white calcite crystals that resemble poker chips. These crystals grew differently because of the cooling rate of the mineral-rich solution....

This beautiful sample was recently collected from Pulaski County and donated because of the rare crystal shapes of the minerals. This cavity, or vug, was found in an igneous d**e in the Jackfork Fo…

10/22/2025

https://arkansasgeological.wordpress.com/2025/10/13/happy-mineral-day/

Happy Earth Science Week. We are celebrating each day’s theme and starting the week with: Cookeite – A lithium mineral Cookeite with iron-coated quartz crystals. Iron-coated quartz crys…

10/22/2025

https://arkansasgeological.wordpress.com/2025/10/14/hiding-in-plain-sight-using-remote-sensing-to-find-abandoned-coal-mines/

Today is Earth Observation Day of Earth Science Week! To celebrate, we’d like to share an example of how geologists at the OSG used remote sensing in a recent project. For the past couple years, th…

10/22/2025

https://arkansasgeological.wordpress.com/2025/10/15/happy-national-fossil-day-2/

Today we are highlighting Fossilized Oysters Left shell or valve, around 5 inches long Right, internal portion of shell or valve, around 3.5 inches long This fossil oyster is a type of mollusk that…

10/22/2025

https://arkansasgeological.wordpress.com/2025/10/16/happy-geoscience-for-everyone-day-2/

We’d like to use today to highlight a field trip we had the opportunity to lead at the 2025 South-Central Geological Society of America section meeting. Multiple participants were led to historic m…

10/22/2025

https://wp.me/p3IMVW-X7

The most detailed geology available for the area to the southeast is from the 1:500,000-scale Geologic Map of Arkansas (Haley et al., 1993). To the northwest, 1:24,000-scale geologic mapping done f…

07/30/2025

https://www.facebook.com/share/v/1HPQUmBBGZ/

05/28/2025

Notice anything a little unusual about this image? This exposure shows two 80-foot benches being worked in the Hatton Tuff Member of the Mississippian Stanley Shale. On the lower bench rocks are dipping to the south, while on the upper bench rocks are dipping to the north. How do we explain this phenomenon? The contrasting dips on the different benches is caused by isoclinal recumbent folding where the fold limbs are nearly parallel to each other. ...

Notice anything a little unusual about this image? This exposure shows two 80-foot benches being worked in the Hatton Tuff Member of the Mississippian Stanley Shale. On the lower bench rocks are d…