Geologic Map of the O'Neill 1 x 2 Quadrangle, Nebraska, with Configuration Maps of Surfaces of Formations (GMC-34) Diffendal, Jr. R.F., Voorhies, M.R., Voorhies, E.J., LaGarry, H.E., Timperley, C.L., Perkins, M.E. (1:250,000; 2008), size 25" x 36". Description: This map is necessarily generalized. It is based primarily on data from 7.5 surficial geologic quadrangle maps of the map area prepared by the authors principally from 1991 to 2000, from Voorhies (unpub. data, 1974), as well as data from test-hole drilling done across the quadrangle by the Conservation and Survey Division, University of Nebraska, and its cooperators over many years since the 1930s. The O'Neill 1 x 2 quadrangle in north-central Nebraska is part of the High Plains section of the Great Plains Physiographic province. The map area is mostly a constructional plain that has been dissected principally since the Pliocene by the rivers and streams that drain the area. Most of the area south of the Niobrara River on the west and south of the Elkhorn River from its headwaters eastward to near the east side of the quadrangle is part of the Nebraska Sand Hills Ecoregion. Colored map with 29 page brochure and CD-Rom available.