Guidebook—Geology and Paleontology of Northwestern Kansas

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Stop 1 to Stop 2

From Monument Rocks we travel south, again crossing the Smoky Hill River. Here the bed of the river is 480 feet lower than our starting point in Oakley. We then travel west back to U.S. 83, passing numerous Niobrara outcrops before we arrive at the Keystone Gallery on the west side of the highway.

color photo of people inside gallery with mosasaur fossil mounted on wall at back

Inside Keystone Gallery.

The gallery is housed in a former church, constructed in 1916 out of local chalk. Although officially named the Pilgrim Holiness Church, the church became known as the Keystone Church, and Bonner and Shelton kept this name for their gallery (Bonner, 2002).

Among the fossils on display inside the one-room gallery is a 14-foot-long fish Xiphactinus audux. Xiphactinus was the largest bony fish that ever lived, with some reaching a length of 18 feet (Bonner, 2002). Its teeth are fairly common fossils in the Cretaceous chalk. These enormous fish had voracious appetites and often ate other fish whole. In fact, some died with their dinners inside of them, as illustrated by the famous "fish within a fish" at the Sternberg Museum of Natural History in Hays, Kansas (Bonner, 2002).

Another important predator in the Cretaceous seas was the mosasaur--a large swimming reptile that sometimes reached 60 feet in length. Mosasaur fossils have been found throughout the Cretaceous chalk, and the gallery has one on display.

color drawing of mosasaur as it may have appeared in life, with long, powerful tail, 2 pairs of flippers, and a reptilian head with many teeth displayed

Mosasaurs were large, swimming reptiles whose fossils are common in Kansas Cretaceous deposits. Kansas mosasaurs ranged in size from the 14-foot Platecarpus to the giant Tylosaurus, which grew up to 60 feet long. The largest Tylosaurus ever found is displayed at the KU Natural History Museum.

The Bonner family has been collecting Cretaceous fossils from the Niobrara Chalk for several generations, since 1928. Some of the specimens they've collected over the years, including a sea turtle and a plesiosaur (a cousin of the mosasaur), are on display in the Sternberg Museum of Natural History (Bonner, 2002).

Stop 2 to Stop 3

From the Keystone gallery we travel south on U.S. 83, climbing back onto the High Plains surface that overlies the Ogallala Formation. We turn north on K-95 and follow it into the oasis-like Ladder Creek valley, descending through rugged outcrops of the Ogallala Formation that surround Lake Scott. We will proceed into Lake Scott State Park, where we will get a look at outcrops of the Ogallala Formation and visit one of the large springs that have created this oasis.

Lake Scott State Park

Listed by National Geographic's Traveler magazine as one of the country's 50 must-see state parks, Lake Scott State Park is located west of U.S. 83, between Oakley and Scott City on K-95. The park's rugged canyons and craggy bluffs stand out from the typical shortgrass prairie of the surrounding High Plains region. The 1,200-acre park with its 100-acre lake is a popular place for boating, swimming, camping, hiking, and wildlife observation.

color photo of lake from above showing surrounding bluffs

Lake Scott, Scott County.

The park officially opened on June 12, 1930, one of the first areas set aside in the Kansas parks system. It averages about 180,000 visitors a year.

In addition to the campsites, swimming beach, playground, and concession area, the park has nature trails that accommodate hikers, horseback riders, and naturalists. Wild turkey, deer, beaver, and bobcat have been found in the park. A privately owned herd of buffalo and elk can be viewed at the south end of the park. The park is also home to the Lake Scott riffle beetle, a very small insect that lives in the well-oxygenated riffles of the park's natural springs. This is the only location on earth in which this species is known to occur.

Ogallala Formation

The park is a good place to see outcrops of the Ogallala Formation, which is well known as an underground aquifer throughout the High Plains. Most of the water pumped for irrigation in the eight-state High Plains region is pumped from the Ogallala Formation.

The Ogallala Formation consists of unconsolidated gravel, sand, silt, and clay that eroded off the Rocky Mountains during late Tertiary times, just a few million years ago. At the park, the Ogallala crops out at the surface as hard, dense sandstones and conglomerates cemented with calcium carbonate, known locally as mortar beds. At the south end of the park, the Ogallala forms a long ridge called Devil's Backbone.

color photo of spring surrounded by willows and other vegetation, with tall rock outcrop in background

Big Spring at Lake Scott, with Ogallala outcrop in background.

Big Spring

Springs of any sort are relatively rare on the arid landscape of western Kansas. Several historic springs have now dried up with the lowering of the water table in the Ogallala Formation, primarily because of irrigation. However, Big Spring, one of the largest springs in the Ladder Creek valley, continues to flow at about 350 gallons per minute, a rate roughly comparable to estimates made in the 1950's, making it among the most productive springs in the western third of Kansas. Water moves through the Ogallala Formation before encountering the relatively impermeable rocks in the underlying Niobara, then comes out here. In addition to their historic importance, the springs in the Ladder Creek valley are also important ecologically, providing habitat for a species of riffle beetle that is only found in this location.

This guidebook is also available in print form as Kansas Geological Survey, Open-file Report 2002-42, from KGS Publications Sales office, 785-864-3965.

Unless noted otherwise, illustrations by Jennifer Sims, Kansas Geological Survey; photographs by John Charlton, Kansas Geological Survey. Text by Liz Brosius, Jim McCauley, Bob Sawin, and Rex Buchanan, Kansas Geological Survey.

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