NPC Students Explore Lake Ouachita

National Park College (NPC) students in Dr. George Maxey’s Physical Geology class and Dr. Sean Hurt’s Earth Science class visited three geologic outcrops on Lake Ouachita last month. Jen Menge of Ouachita State Park helped with the guided tour.

Blakely Dam in Hot Springs National ParkThe field trip began at Blakely Dam. “Blakely Dam exhibits excellent examples of Ordovician age, folded and faulted rocks from the root of the Ouachita Mountains,” said Maxey. He explained the deformities in the rocks are examples of the forces applied in creating the Ouachita Mountains subsequent to deposition during the Ordovician period.

Students identified rock types and were challenged to reconstruct the sequence of events from sediments lying flat on the floor of the Tethyian sea to their present condition.

The trip continued along Highway 7 near the entrance of Hot Springs Village, also in the Ordovician Blakely formation. Students were tasked with locating different types of rock and sharing what technique they used to identify the specimen. Students used a Brunton compass to identify the rock type and measure the dip and direction of the beds.Zebra rock at Lake Ouachita in Hot Springs National park

The field trip continued with a geofloat tour on Lake Ouachita, where students were tasked with interpreting the geology of each outcrop. The tour included Zebra rock where students explored the formative environment of the white quartz secondary deposition in the Ordovician sandstone and discussed the paleohistory of the formation of the Ouachita Mountains, including the plate tectonic collisions between South America and North America.

They continued the tour on the north side of Lake Ouachita in Womble Shale, a recumbent fold. Students saw the intense deformation of the rocks caused by the plate tectonic collisions.Students studying a fossil through a microscope

Checkerboard Island was the final stop on the geofloat tour. Students explored the geology of the island. “Checkerboard Island consists of two formations, the Blakely Sandstone and Womble Shale. A sharp contact can be seen between the two formations,” said Maxey. While on the Island, students found fossil remains of several species of Graptolites and two species of bivalve.

The group received permission to take the impressions back to the NPC science lab to attempt to identify the species from the impressions. “The impressions exhibited the form and shape of either a brachiopoda or pelecypoda,” Maxey noted. Students examined the fossil impressions under a microscope and tested for primary carbonate residue but the impressions were too eroded for positive identification.