Guidebook—Geology and Paleontology of Northwestern Kansas
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Little Jerusalem, Logan County.
Stop 3 to Stop 4
From Stop 3 we will continue south along the west side of Lake Scott and pass the El Cuartelejo ruins. Turning north, we pass the dam on Ladder Creek that forms Lake Scott and then continue down the valley where the contact between the Cretaceous Niobrara Chalk and overlying Ogallala Formation is visible in the canyon walls.
After crossing Chalk Creek, we pass a cluster of chalk monuments known as the Little Pyramids. After turning west and again north, we will see a large area of chalk badlands called Little Jerusalem. This is the largest exposure of Niobrara Chalk in the state.
As we skirt the south and west edge of the Smoky Valley Ranch, we will again cross the Smoky Hill River. We will enter the ranch from the north and pass the site of an old quarry in an orange-colored outcrop of Niobrara Chalk.
Stop 4--Smoky Valley Ranch
With the acquisition of the Smoky Valley Ranch in Logan County in January 1999, Nature Conservancy, Kansas Chapter, established a 16,800-acre (more than 25 square miles) preserve. This preserve is large enough to support much of the rich diversity of animals and plants that inhabited the shortgrass prairie region. Most of the shortgrass prairie that once covered western Kansas has been cultivated over the past century.
In addition to the Smoky Valley Ranch Preserve, significant remnants of native prairie remain along the Smoky Hill River and its tributaries in Wallace, Logan, and Gove counties. Many of these prairies have been well managed as grazing pastures for decades. However, periodic dislocations in the cattle market and improved dryland crop varieties have induced increasing numbers of landowners to convert their native pastures to cropland.
The ranch is characterized by chalk bluffs overlooking the Smoky Hill River, large expanses of grassland, and rocky ravines. The breaks along the upper reaches of the Smoky Hill River represent the transition zone between the mixed grass and shortgrass prairie regions.
The oldest rocks exposed at the Smoky Valley Ranch Preserve belong to the Smoky Hill Chalk Member of the Niobrara Chalk (see stratigraphic column), the same rock that makes up Monument Rocks. The Smoky Hill Chalk Member crops out at several localities on the preserve. The largest areas, some covering tens of acres, are found along the Smoky Hill River, but the three main north-south tributaries that cross the preserve north of the river also contain some excellent chalk exposures. These badlands offer scenic views of steep bluffs, steep-walled canyons, and pinnacles carved from the soft chalk by the action of wind and water.
As mentioned earlier, chalk is a soft, porous, very fine grained limestone that forms from the seafloor accumulation of tiny marine organisms that lived near the ocean's surface. The resulting sediment--a soft limy ooze--was the perfect medium for engulfing and preserving the remains of other animals--such as fish, sharks, turtles, clams, and marine reptiles--that fell to the bottom of the sea.
The upper part of the Smoky Hill Chalk Member was quarried for building stone at several locations about 3 miles north of the preserve's ranch house. Saw marks, cut blocks, and other remnants of the quarry operation can be seen at three different sites in this area. The cap rock, a harder, more resistant layer near the top of the Smoky Hill Chalk, was the stone of choice for building. When first uncovered, the stone is soft enough to cut with a saw; after it is exposed to the air, it becomes harder. Examples of structures built from the chalk are the ranch headquarters and the abandoned house near Blue Knob, about a mile southwest of the headquarters.
Rocks in the Pierre Shale, also Cretaceous in age, overlie the Niobrara but crop out only in the northern part of the preserve (Sawin et al., 1999). The uplands are mantled by sand and gravel and windblown silt (loess) deposited during the Pleistocene Epoch, which began about 1.8 million years ago. The youngest rocks on the preserve are sand dunes in the uplands and alluvium in the Smoky Hill River valley that were deposited during the last 10,000 years, during the Holocene Epoch.
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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