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Field Division of Education Outline of the Geology and Paleontology of Scotts Bluff National Monument and the Adjacent Region |
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GEOLOGIC TIME SCALE (Modified from Schuchert)
| Eras | Periods | Duration | Biologic and Climatic Changes | Ages | |
| Cenozoic | Pleistocene (Epoch) | Periodic glaciations. Dawn of social life and industry among men. Extinction of large mammals. | Age of Man | ||
| Pliocene (Epoch) | 5% | Cooling climate. Changing of man ape into man. | Age of Mammals | ||
| Miocene (Epoch) | 5% | Culmination of mammals and land floras. | |||
| Oligocene (Epoch) | 2% | Rise of Anthropoids. Last of archaic mammals. | |||
| Eocene (Epoch) | Spread of modernized mammals. Dawn of modern life. Rise of grasses, cereals, fruits. Expansion of archaic mammals. | ||||
| Mesozoic | Cretaceous | 4% | Last of the Ammonites. Extinction of Dinosaurs, Pterodactyls, and toothed birds. Rise of archaic mammals and birds. Spread of flowering plants and modern insects. | Age of Reptiles and Ammonites | |
| Jurassic | 2% | Rise of toothed birds and spread of Pterodactyls. Spread of primitive mammals. Culmination of ammonites. | |||
| Triassic | 1% | Rise of Dinosaurs, Pterodactyls, and primitive mammals. Spread of cycads and conifers. | |||
| Paleozoic | Permian | 2% | Periodic glaciations in southern hemisphere. Extinction of Trilobites and Paleozoic corals. Primitive insects. | Age of Amphibians | |
| Carboniferous | Pennsylvanian | 2% | Warm humid climate with extensive coal making. Dominance of spore floras. Spread of reptiles | ||
| Mississsippian | 2% | Spread of ancient sharks and culmination of crinoids. | |||
| Devonian | 2% | Rise of amphibians, marine fishes, and primitive ammonites. First spread of forests. | Age of Fishes | ||
| Silurian | 1% | Rise of air-breathing invertebrates. Spread of Paleozoic reef-corals. First known occurrence of land plants. | |||
| Ordovician | 3% | Rise of fresh-water fishes and of corals. Spread of molluscs. Culmination of trilobites. | Age of Marine Invertebrates | ||
| Cambrian | 4% | Rise of shell-bearing molluscs. Dominance of trilobites. First appearance of well-known marine faunas. | |||
| Proterozoic Era | 75% | Era of primitive marine life. An early and late glacial period. | |||
| Archeozoic Era | Era of the oldest known life. Geologic history very obscure. | Age of Larval Life | |||
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Last Modified: Tuesday, Feb 21 2006 10:00:00 am PDT |