Around it is spread the sedimentaries of the Mississippian, and over it the Pennsylvanian formations, for the greater part of Nebraska took another plunge into the sea. Eastern Nebraska came up from the ocean, with almost all of the North American continent at a little later date. But an estuary from the Pacific covered that part of the state west of the one hundredth meridian, and it also covered western Kansas, Oklahoma, through the varying ages, came down to a time comparatively and geologically modern.
The course massive buff and grey Dakota sands, some places five hundred feet thick, were spread over Nebraska, indicating a moving body of water with currents sufficient to carry away the silts, and also indicating that eastern Nebraska was also again under the water surface.
At the close of the carboniferous age, internal forces again disturbed the Omaha. Lincoln, Wichita range, but it never reached full proportions, owing to the weight of covering depositions. Buried under the sedimentaries of
HISTORY OF WESTERN NEBRASKA
eastern Nebraska and central Kansas, it still exists, a twin of the Ozarks, lower in altitude, and covering a much larger area.
When the more violent disturbances shook the fractured region, great slabs of granite one hundred feet thick and miles in area, were in places thrust out almost horizontally through the comparatively newer rocks and shales, and these granitic intrusions have puzzled geologists, and turned aside the tides of oil prospectors from time to time. Granite and Red Beds have been discouraging features to oil geologists : yet daring prospectors have drilled through these granite barriers into the shales below,. and others have found best qualities of petroleum in Red Bed anticlines.