Nebraska Badlands

by

Zhilin Li, Yuanyuan Zhou, and Gayla R. Corley
Dr. James S. Aber, Instructor

Table of Contents
Introduction Site Description
Methodology Geomorphology
Conclusions Photo Gallery
References



Figure 1 Overview of the Nebraska Badlands. Note the three levels of erosion in the background and the stream channel in the foreground.
Photo by J.S. Aber and ES 546 class students, 2015.


Introduction

Toadstool Geologic Park is located in the Nebraska’s Badlands in the Western Nebraska Oglala National Grasslands (www.NebraskaTravels.com). Water and wind over millions of years created the unusual rock formations found in the Park. The geologic formations were created by the sandstone rocks and the clay stems by erosion. The park was explored by hiking the trails and climbing the hill sides looking at the terrain.

There are many channel complexes in the Chadron Formation. The hills are steep and difficult to climb. A view from the top of the hill is different from the foot of the hills. Vertebrate fossils are found on the top of the hill, but they cannot be collected in the National Grasslands.

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Site Description

The United States is divided into ecoregions, Figure 2. The largest are three ecosystem domains: 1) the dry domain, 2) the humid temperate domain, and 3) the humid tropical domain (USDA). Each of these three domains is further divided into divisions and provinces. The Nebraska Badlands are located in the dry domain. In the dry domain the annual precipitation does not exceed the evaporative lose. Normally permanent streams do not originate in dry climate zones. Semi-arid climates are found in approximately one fourth of the world’s land surface (Bailey, 1980).


Figure 2 Ecoregions of the United States with study site marked by an asterix. Adapted from USDA Forest Service.

The division where the badlands is located is the Temperate Steppe Division (Bailey,1980). It is characterized as a semiarid continental climate and one month of the year’s average temperature is below 0° C (32° F). Summers are warm to hot and the winters cold and dry. Vegetation is sparse and short grass prairie with the grasses growing in clumps. There are some shrubs and occasionally a few trees. The soil is exposed due to the sparse ground cover of vegetation. Buffalo grass (Buchloë dactyloides) is common in steppe lands. Forbs commonly found include sunflowers (Helianthus annuus L) and locoweed (Astragalus and Oxytropis spp.).

The Temperate Steppe Division of the dry domain ecosystem is further divided into provinces. The Nebraska Badlands is located is the Great Plains-Palouse Dry Steppe Province (Bailey, 1980). Characteristics of this province are rolling plains and tablelands. The area also has buttes, sharp relief, canyons, eroded ravines and meandering ephemeral streams. It is characterized by short grasses, occasional trees, and scrub brush.

The Nebraska Badlands lie in a valley created by the White River and is approximately 160 km (100 miles) long and 80 km (50 miles) wide and the depth of the fill of the valley before erosion was 150 m (500 feet) (Beasley, 2015). Prior to erosion the valley contained approximately 1.9736*10^3 cubic kilometers (4.735*10^3 cubic miles) of deposited materials. This figure was obtained multiplying the length of the valley times the width of the valley times depth of the deposited materials. Depositional materials were transported from the Rocky Mountain Region by water. Badlands soils were predominately eroded from the Pierre Shale and extend into the South Dakota Badlands.

Through direct observation it was noted the badlands soil is light gray and the siltstone and sandstones are the same color. The sandstone tops the hills and is resistant to erosion. One unique feature noted is the toadstool shaped rocks at the Toadstool Park. They were created where sandstone rested on top of a siltstone column formed when water and wind eroded the soils from around the sandstone cap. The wind and water continued to erode under the cap stone until the column is decreased in size and the sandstone cap becomes too heavy for the column to support and it collapses.

Badland is the soil type of the slopes and hills, (Soil Survey Staff). Here the slopes are from 3 to 50 percent and consists primarily of siltstone or silty and clay shales. These barren soils with steep slopes make up approximately 75 percent of the badlands. Erosion is extreme since water runoff is rapid and scant plant cover is in place to slow down the process. Some grass and weeds grow in the low lying areas and ravines, but it is sparse and not suitable for grazing livestock. Wildlife finds some protection in these areas and human use the area for recreation.

Other soil types associated with the Badland soils are the Orella silty clay loam and the Orella-Badland complex (Soil Survey Staff, 1973). The soils on the uplands are the Orella silty clay loam and these areas have 3 to 30 percent slopes. These soils have limitations due to poor grass cover, shallow rooting zone, rapid water runoff and alkalinity. Most streams in the Badlands area are ephemeral and only contain water doing rainy periods of time. It is not suitable for cultivation and is used as rangeland for cattle. Orella-Badland complex soils gave slopes of 3 to 50 percent and erosion is rapid as it is located on upland ridge tops and hillsides. The Orella soils support grasses suitable for rangeland while the Badland soils have little or no vegetation.

The pedogenic processes in these three types of soils are calcification and in poorly drained sites salinization. Precipitated calcium carbonate is in excessive amounts and the soil is highly alkaline. The soil type is typically Mollisols and has only small amounts of humus since vegetation cover is limited.

Climate has been a large part of the forming of the Nebraska Badlands as it contributed to the deposition of materials filling the White River valley. This occurred during the late Cretaceous Period (67 to 75 million years ago) through the Late Eocene (34 to 37 million years ago) and Oligocene Epochs (26 to 34 million years ago). There was a deposition of 150 m (500 feet) of material during these time periods.

Erosion continues today in the Nebraska Badlands and the actions of wind and water contribute the largest influence. In the winter freezing and thawing help break up the siltstones and sandstones increasing the erosion by water in the spring. The rain shadow of the Rocky Mountains is the factor causing the arid conditions of the Nebraska Badlands. Table 1 contains present day statistics of the weather in Dawes County (USA.com).

Table 1. Average Annual Dawes County Weather
TemperaturePrecipitationSnowfall Humidity
HighLowAverage AverageAverageAverage
16.3 C---61.4 F1.2 C---34.1 F 8.8 C---47.8 F446.3 mm---17.57 inches1103 mm---43.42 inches81.60%

The Nebraska Badlands also known as the White River Badlands are famous worldwide for fossil deposits. Volcanic ash in the soil is a silicate and it replaced the bony material of the animals causing them to be well preserved. The fossils are diverse and the faunal list is large.

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Methodology

Information was gathered from the Nebraska travels website and a literature search of writings of early geologists and recent literature were reviewed. The area was explored by direct observation hiking the trails and climbing the hill sides looking at the terrain. Photographs were taken at the top and the foot of the hills by personal camera. Aerial photographs were taken of the area using the kite and a S 70 camera with a KAP rig. The area was also explored by directly observation by hiking the trails and climbing the hillsides looking at the terrain.

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Geomorphology

The stratigraphy starts with the oldest of the highly fossiliferous rock units, Oligocene age Chadron and Brule Formations, and then the Miocene age rocks of the Arikaree Group, Figure 3.


Figure 3 Composite chart of the stratigraphy of Toadstool Geologic Park area superimposed over a photo taken near the campground (Scultz and Stout, 1955).

Coarse-grained sand was carried from the Rocky Mountains and the Black Hills, and deposited in the river valley. Silt from the west and north was deposited in the flood plain of the river. Over time, this silt became siltstone and the sand became sandstone capping the hilltop of the Nebraska Badland. These changes occur over hundreds of thousands of years as the river changed course and left alternating layers of sandstone and siltstone. The evidence of paleorive is in the presence of sandstone and the siltstone beds deposited on the flood plain, Figure 1.

As flora and fauna died, they were buried in the accumulated volcanic ash and silt. They were fossilized and the silica minerals from the ash filled the pore spaces and strengthen the bone, so weathering does not destroy the fossil as easily.

About 10 million years ago, this region was uplifted and the climate became drier (Beasley 2015). Since then, the process of all layers that had been built up over millions of years, about 150 meters (500 ft) of sediment has been eroded away and this process continues today. The softer siltstone is less resistant to the forces of erosion than the hard sandstone. A protective cap of sandstone over a stem of siltstone below created the formation known as toadstools. The siltstone stem erodes more quickly than the sandstone and the weight of the sandstone cap collapses the toadstool.

The Brown Siltstone member, the Whitney member, and most of the Orella member of the Brule Formation are completely eroded away. The Chadron Formation is partially exposed. The Chamberlain Pass Formation (CP) and the lower purplish white ash layer have not yet been exposed here. The Chadron Formation ranges up to 90 meters (300 feet) in thickness and it consists primarily of fine-grained, light-brown to pink clay stones. Widespread deposits of volcanic ash formed these rocks, as time goes by, most of these rocks weathered into clays.

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Conclusions

In conclusion, as flora and fauna died they were preserved as fossils. Approximately 150 m (500 feet) of sediment was deposited has been eroding away. The processes of erosion continue today. It is distinctive landscape with several different geological features and internationally recognized fossils.

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Photo Gallery


Nebraska Badlands at Toadstool Park. Photo by Zhilin Li.

Click on the small pictures for an enlarged photograph.


Photograph from Badlands
in Sioux County, 1894.
University of Nebraska—Lincoln.


Butte in White River Valley
from the 1890's, note men
standing on top. Historic
family photograph, from
G.R. Corley collection.


Twisted dead scrub brush
in gray Badlands soils. Photo
by G.R. Corley.


Looking to northwest at
Toadstool Park. Note the large
round sandstone caps
in foreground. Photo
by Zhilin Li.


Steep ravines no
ground cover.
Photo by Zhilin Li.


Scant foliage and steep
sided ravines illustrate
high erosion with little or no
soil protection. Photo
by G.R. Corley.


View of Toadstool Park
area. Red astrick is
campground. Adapted
from Google Earth.


Note sparse grass and scrub
brush in the foreground
on the Orella-Badlands
Complex soils. Photo
by G.R. Corley


Weathering clod of siltstone,
note color of siltstone
and soil. Photo by
G.R. Corley.


Chalcedony veins, photo
G.R. Corley.

Kite aerial photograph (KAP)
across landscape. Lakes in the
background and foreground
vegetation on Orella-Badland
Complex soils. Photo by
J.S. Aber and ES 546 Class.


Ephemeral stream coming
from Badlands. KAP by
J.S. Aber and ES 546 Class.


Overview illustrating the
rugginess of Badlands. KAP
by J.S. Aber and ES 546 Class.


Moist area in ephemeral
stream bed with animal
tracks, possible spring.
Photo by G.R. Corley


Fossil fragments found
on sandstone on hilltop.
Photo by Zhilin Li.


Colored bands in hills
were deposited at different
time intervals with different
mineral content. Photo by
G.R. Corley


Sandstone block resting on
the remains of a pedestal
eroded away by wind and
water. Photo by Yuanyuan
Zhou

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References

Bailey, R. G. 1980.Description of the ecoregions of the United States. USDA Forest Service. Accessed online November 2015.

Beasley, Barbara, Toadstool Geologic Park (Nebraska). US Department of the Interior. National Park Service. Accessed online November 2015.

Dawes County Weather. USA.com. Accessed online November 2015.

Geologic Formations. National Park Service. Accessed online November 2015.

Photograph Toadstool Park Sioux County Badlands, 1894. Conservation and Survey Division University of Nebraska—Lincoln. Accessed online November 2015.

Schultz, C.B., and Stout, T.M. 1955. Classification of Oligocene sediments in Nebraska. Bulletin of University of Nebraska State Museum 4:17-52

Soil Survey Staff, Soil Survey of Dawes County Nebraska, 1973, Natural Resources Conservation Service, Official Soil Series Descriptions. United States Department of Agriculture. Accessed online November 2015.

Toadstool Geologic Park. www.NebraskaTravels.com Accessec online November 2015.

USDA.Ecoregions of the United States. Forest Service. Accessed online November 2015.

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This webpage was created to meet the partial requirements of ES 546 Field Geomorphology at Emporia State University, Emporia, Kansas, and is the property of the authors. For more information contact the authors: Zhilin Li, Yuanyuan Zhou, and Gayla R. Corley.

Created November, 2015, for the Earth Science Department, at Emporia State University, Emporia, KS. Latest update December 2015.

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