Smithsonian Institution Logo Gavins Point Dam—Lewis & Clark Lake
Geology, Paleontology, Archeology, History
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In the area of the Lewis and Clark Lake, the valley of the Missouri River is cut into the Upper Cretaceous Niobrara chalk (or limestone), a geologic formation rich in fossil remains of fishes, marine reptiles, flying reptiles, and toothed birds. It was within this very area, of Lewis and Clark Lake, in fact, that the first fossil skeleton from the whole Missouri River Basin was discovered and reported.

Lewis and Clark, on their trip up the Missouri in 1804, discovered a fossil skeleton, apparently in the Niobrara chalk in the Gavins Point area. The description of this discovery by these early explorers indicates that the bones were those of a marine reptile, approximately 45 feet long. Unfortunately, the specimen was not collected, but similar specimens have been found in the area during the past fifty years and have been preserved in various museums. The geological deposits in this basin are now known throughout the world for their abundant fossils.

In 1862, F. B. Meek and F. V. Hayden of the U. S. Geological Survey of the Territories gave the name "Niobrara" to the chalky limestone and silt which is exposed along the Missouri near the mouth of the Niobrara River in the vicinity of Lewis and Clark Lake. This Niobrara formation was deposited during the geologic period known as the Cretaceous, some 100 million years ago, when the area was covered by a shallow, inland sea. During those ancient times, various marine fishes, reptiles, and invertebrate animals lived in the warm, oceanic waters here, while the dinosaurs were living on the lands to the east and west of this sea. The fossilized teeth of giant sharks and lizards are commonly found in the region today.

Somewhat later, when the sea had disappeared, quite different sorts of animals roamed the reaches of what is now the Lewis and Clark Lake. Occasionally, rhinoceros bones are found here, and these, along with certain other animals of the time, indicate that deposits of the geologic period known as Pliocene once covered the region. A few good Pliocene exposures, ranging in age from two million to six million years, are to be found near the Gavins Point Dam.

Still later deposits of the Great Ice Age or Pleistocene geologic period are well exposed in the area surrounding the lake. All four of the major glaciers of the Pleistocene period, known as the Nebraskan, Kansan, Illinoian, and Wisconsin, in that order from earliest to latest, were present in this locality. The actual glacial till—rocks, earth and trash dumped on the land as the glaciers melted—left by these tremendous continental glaciers can be observed in exposures in the region today. The fossilized remains of caribou, musk oxen, wooly mammoths, mastodonts, giant moose-like deer, and other arctic animals have been found nearby in northeastern Nebraska and southeastern South Dakota. The discovery of these fossil specimens indicates that arctic conditions prevailed in the area when these animals were alive. It may seem difficult, now, to realize this as one visits the area on a hot summer day.

There were times between the great glacial advances, however, when the climate was even warmer than it is today. During these interglacial periods, camels, horses, southern mammoths, giant bison, peccaries, and ground sloths lived along this portion of the Missouri River Valley. The bones of all of these warm-climate animals are commonly found in the interglacial deposits here. These glacial and interglacial periods represent the latest climatic and geologic period prior to the Recent, or present-day climate, and cover the period from half a million to some nine or ten thousand years ago. During the very latest stages of the Pleistocene, man himself appeared on the scene and lived in various parts of the Central Plains area in time to hunt and gain his living from some of the typical animals of the Ice Age. Within the immediate area of Lewis and Clark Lake, however, none of the remains of these Early Man, or Paleo-Indian campsites have been found.

Wild life still lives in abundance in the region today. Deer, for example, are found in great numbers in the hilly country of the "Devil's Nest" to the south of Lewis and Clark Lake. A splendid natural habitat group, showing the White-tailed Deer in the "Devil's Nest" region, is on display at the University of Nebraska State Museum in Lincoln, Nebraska. In this exhibit, actual mounted specimens of deer are shown walking over gravels which contain the bones of extinct animals of the past, such as Pleistocene camels and horses. The actual prehistoric bones are exhibited just as they appear on the hills to the south of the present lake at Gavins Point. It is truly rewarding to view this area today and realize that many of the great museums of the country have secured some of their choicest exhibit materials in this very locality.

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Last Updated: 08-Sep-2008