October 7, 2010

Agate Fossil Beds National Monument, Nebraska

Located in a very remote part of western Nebraska is the Agate Fossil Beds National Monument. How remote? Well, about 25 miles north is the only town in Souix County, Nebraska named Harrison with a total population of about 300 people. The next town from Agate is about 40 miles to the south on the outskirts of Scottsbluff.

As such, this is remote, unarable, grassland dominated by HUGE cattle ranches and not much else. There is virtually no surface water, except for the Niobrara River which begins in this region, as it taps the enormous Oglalla Aquifer, and runs hundreds of miles to the Missouri River.

Back in the late 1800's a rancher named James Cook discovered some bones sticking out of a hill on his ranch next to the Niobrara River. He contacted the University of Nebraska and excavations began. What they discovered was an 19 million year old waterhole containing the skeletons of hundreds of animals.

At this time, this region of North America was a large seasonal savannah similar to East Africa today. The evidence points to a major drought that resulted in waterholes drying up and the nearby vegetation being eaten or dying and leaving these animals starving. They migrated to the waterhole for water, but had nothing to eat and ended up dying by the dozens in the mud. These scenes are seen in Africa today.

The animals found out here include ancient camel-like animals, giant pig/wildebeest-like scavengers, a huge animal called a "" that is unlike anything alive today, and carnivorous "bear-dogs" which are also extinct.

Ancient Rhinos were found here

Preserved footprints in this mud wallow that filled in with sediment from ancient rhinos
In another area of Agate Fossil Beds, are 22 million-year old "Devil's Corkscrews" which were the burrows of an ancient land beaver that lived in colonies similar to prairie dogs today. At first, scientists thought these were ancient root systems, until they discovered skeletons inside. These burrows eventually filled in with sand.

Devil's Corkscrews by these ancient burrows

The body of these prairie dog-like beavers in the burrows

These lines are fossilized roots and insect and small animal burrows
There are also fossilized root-systems and small animal burrows that tell the story of the soil and ecosystem of the region. These fossilized soils indicate the region was mostly a grassland or shrubland that was very dry and seasonal in nature. Not unlike Nebraska today, only hotter and more subtropical.

The flat plain was the original level of the Great Plains. These fossils were exposed as erosion worked its way down into the older sediments.

The two hills to the left are the quarries of those ancient waterholes. They are called University and Carnegie Hills. The middle area, where the cuts are, are the fossil sites. We hiked 2.7 miles roundtrip to check them out.

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