Mineral Resources On-Line Spatial Data
Mineral Resources > Online Spatial Data > Geology > by state > Nebraska Geology
Geologic units in Knox county, Nebraska
- White River Group (Phanerozoic | Cenozoic | Tertiary | Oligocene) at surface, covers 0.4 % of this area
Clay, some claystone, silt and siltstone. Predominantly greenish gray and volcaniclastic. Other occurrences are greenish gray to white and bentonitic. Local channel sandstone at base. Aprox thickness 195 ft.
- Ogallala Group or Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers 44 % of this area
Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate, sandstone, and siltstone.
- Alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area
Clay to boulder-size clasts with locally abundant organic material. Thickness up to 75 ft (23m).
- Niobrara Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 6 % of this area
Argillaceous chalk, limestone and shale. Chalk is medium gray to white, interbedded with thin layers of chalky shale; contains many fossil clams, oysters, and formanifera. Limestone is light gray to medium gray and yellowish gray, interbedded with medium-gray chalky shale; also contains fossil clams, oysters, and formanifera. Bedding plans commonly marked by thin layers of gypsum and locally a thin bed of red flint occurs at top of unit. Approx. max thickness 570 ft.
- Dam (None) at surface, covers < 0.1 % of this area
- Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 49 % of this area
Mostly medium to dark-gray, brownish-gray, and black, fissle clay shale. Locally grades to thin beds of calcareous, silty shale or claystone, marl, shaly sandstone, and sandy shale. Locally contains thin seams of gypsum and sparse selenite crystals. Approx. max thickness 1970 ft.
- Till, Stagnation Moraine (Phanerozoic | Cenozoic | Quaternary | Pleistocene [Upper Wisconsin]) at surface, covers < 0.1 % of this area
Heterogeneous, clay with silt to boulder-size clasts of glacial orgin. A geomorphic feature that is characterized by hummocky terrain with abundant sloughs resulting from stagnation of ice sheets. Composite thickness of all Upper Wisconsin till may be up to 300 ft (91 m).