By Christopher Liner and Shelby Gill / Photos by Chieko Hara
Christopher Liner watched a business student crouch down to inspect the samples, one hand on limestone from De Queen and another on a cylindrical core sample from Little Rock — his vision for the GeoLab cemented.
“His arms are spanning the Cretaceous-Tertiary Boundary,” beamed Liner, the Maurice F. Storm Endowed Chair in Geosciences. “Those rocks are 150 miles apart. Here, you can touch both, and you’re standing, in a sense, at the time when the asteroid hit ending the age of the dinosaurs.”
GeoLab, created by Liner, Mac McGilvery, adjunct professor in geosciences, Carl Smith, professor of landscape architecture, and alumna Jenny Burbidge (B.L.A.’10), is a new outdoor installation in Gearhart Hall’s lower-tier courtyard that features 26 geological samples from across Arkansas.
Of quartz, we mined Liner’s knowledge of the rocks to hear the stories behind the stones. Pull out your intellectual pickaxe to see if you can unearth the rugged history of each sample.
1. Which sample was walked across by dinosaurs during periods of low tide?
2. Which sample was collected from the Arkansas State Capitol?
3. Which sample was meant to be a capstone on a U of A campus gate?
4. Which sample relates to bluff dwellings used to shelter indigenous people?
5. Which sample is sold as a surgical instrument edge that is sharper than steel?
6. How many GeoLab samples were formed when humans lived on Earth?
Bonus Questions:
7. Which rock in the GeoLab is not from Arkansas?
8. Which sample is purposely pointed toward Dean Coon’s office?
1. Which sample was walked across by dinosaurs during periods of low tide?
Sample 06: Cretaceous De Queen Limestone (100-125 Myr) / Gypsum, a key component in wallboard, is sourced from De Queen, Arkansas, home to one of the country’s largest manufacturers. In 2010, while extracting gypsum, dynamite was used to break through limestone, revealing dinosaur footprints on the shattered rocks. Although our GeoLab doesn’t possess a sample with a footprint, our De Queen Limestone boasts fossilized shells and burrow tracks from creepy, crawly things.
2. Which sample was collected from the Arkansas State Capitol?
Sample 03: Paleocene Midway Limestone (56-66 Myr) / Sample 03 is a cylindrical core that was extracted from the Arkansas State Capitol site more than four decades ago using a highway department boring machine. This limestone sample holds a significant place in geological history. It dates shortly after the Cretaceous-Tertiary boundary, a period marked by an asteroid impact that led to the extinction of dinosaurs.
3. Which sample was meant to be a capstone on a U of A campus gate?
Sample 12: Mississippian Batesville Sandstone (323-330 Myr) / Originally commissioned by the U of A as a replacement capstone for a wall column, the campus rejected the sandstone pyramid due to a flaw on its surface. The GeoLab then adopted the sample on account of its prominent colored bands, which demonstrate the Liesegang phenomenon caused by mineralized fluid moving through the rock.
4. Which sample relates to bluff dwellings used to shelter indigenous people?
Samples 17 & 18: Mississippian St. Joe Limestone (346-358 Myr) / Limestone and chert, found in the St. Joe Formation, which spans northern Arkansas, southern Missouri and northeastern Oklahoma, formed caves and overhangs that sheltered indigenous people of Arkansas from the elements at least 10,000 years ago. Sample 17 is a weathered example, while sample 18, from the same location, shows fresh, unweathered rock faces.
5. Which sample is sold as a surgical instrument edge that is sharper than steel?
Samples 15 & 16: Mississippian Arkansas Novaculite (346-358 Myr) / Novaculite contains very fine quartz grains, allowing it to sharpen knife edges or be honed to a surgical edge. Indigenous people, such as the Quapaw, Osage, Caddo, Tunica, Chickasaw and Natchez tribes, utilized novaculite for use in creating spears, arrow points, knife blades, drills, scraping tools and axe heads. Both GeoLab samples illustrate the color variation within novaculite.
6. How many GeoLab samples were formed when humans lived on Earth?
Sample 01: Holocene Travertine (12,000 yr) / Only 1, and it is Sample 1. The next youngest, Sample 2 Tertiary Bauxite, is 34-60 Myr old, long before the first humans appeared on Earth about 2.8 Myr ago. This unusually large and pure specimen of travertine was collected by the Arkansas Geological Survey near Hot Springs and is on permanent loan to GeoLab (along with samples 3 and 24).
Bonus Questions:
7. Which rock in the GeoLab is not from Arkansas?
Igneous Metavolcanic Rock (1.8 Bya) / The gravel blanketing the floor of the GeoLab is an igneous metavolcanic rock from a quarry near Stratford, Wisconsin, and it was chosen to match the gravel under the Curvahedra sculpture in the upper landing of Gearhart Courtyard. It is also the oldest rock in the GeoLab at 1.8 Byr. Since no igneous rock is exposed in Arkansas this gravel represents the igneous rock underneath the entire North American continent.
8. Which sample is purposely pointed toward Dean Coon’s office?
Sample 22: Ordovician Powell Dolomite (458-470 Myr) / Affectionately referred to as “the Wedge,” Sample 22 is sandy Dolostone that features a ripple lamination in relief on its surface attributed to tidal currents. Purposely pointed by Liner at Dean Coon’s office, the Wedge’s orientation nods to her collaboration on the space and support of the GeoLab project.
