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Years Ago |
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C E N O Z O I C |
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Holocene | 10,000 | Current | 10,000 | Glacial drift, alluvial deposits, loess, dune sand, volcanic ash |
| Pleistocene | 1,600,000 | 10,000 | 1,590,000 | |||
| Tertiary | Pliocene | 5,300,000 | 1,600,000 | 3,700,000 | Alluvial deposits, limestone, volcanic ash, bentonite, diatomaceous marl, opaline sandstone. | |
| Miocene | 23,700,000 | 5,300,000 | 18,400,000 | |||
| Oligocene | 36,600,000 | 23,700,000 | 12,900,000 | |||
| Eocene | 57,800,000 | 36,600,000 | 21,200,000 | |||
| Paleocene | 66,400,000 | 57,800,000 | 8,600,000 | |||
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M E S O Z O I C |
Cretaceous | 144,000,000 | 66,400,000 | 77,600,000 | Limestone, chalk, shale, clay, sandstone, conglomerate, outcropping igneous rock | |
| Jurassic | 208,000,000 | 144,000,000 | 64,000,000 | Sandstone, shale (mostly subsurface). Siltstone, chert and gypsum | ||
| Triassic | 245,000,000 | 208,000,000 | 37,000,000 | |||
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P A L E O Z O I C |
Permian | 286,000,000 | 245,000,000 | 41,000,000 | Limestone, shale, evaporites, sandstone, chert, siltstone, dolomite, red beds | |
| Pennsylvanian | 320,000,000 | 286,000,000 | 34,000,000 | Shale, limestone, sandstone, coal, chert and conglomerate | ||
| Mississippian | 360,000,000 | 320,000,000 | 40,000,000 | Limestone, shale, dolomite, chert, oolites, sandstone, siltstone | ||
| Devonian | 408,000,000 | 360,000,000 | 48,000,000 | Subsurface only. Limestone, shale, sandstone | ||
| Silurian | 438,000,000 | 408,000,000 | 30,000,000 | Subsurface only. Limestone | ||
| Ordovician | 505,000,000 | 438,000,000 | 67,000,000 | Subsurface only. Dolomite, sandstone | ||
| Cambrian | 570,000,000 | 505,000,000 | 65,000,000 | Subsurface only. Dolomite, sandstone, limestone, shale | ||
| PreCambrian | 4,500,000,000 | 570,000,000 | 3,930,000,000 | Subsurface only, Igneous and metamorphic rocks | ||