Denver Basin

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The Denver Basin is a subterranean geologic formation located in east-central Colorado in the United States. It underlies the Denver-Aurora Metropolitan Area on the eastern side of the Rocky Mountains.

The basin consists of a large syncline of stratified Mesozoic sedimentary rock layers, running north to south along the east side of the Front Range from the vicinity of Pueblo northward to Wyoming. The sag is deepest near Denver, where it reaches a depth of approximately 13,000 (3900 m) ft below the current surface. According to current geologic theory, the basin starting forming as early as 300 million years ago, during the Colorado Orogeny that created the Ancestral Rockies. It was most likely further deepened in Tertiary time, between 65 and 45 million years ago, during the Laramide orogeny that created the modern Colorado Rockies. In particular, the uplifting of the Rockies in the Front Range caused the crust near Denver to buckle downward on the eastern side, deepening the basin. The basin later became filled with erosional sediment from the Rockies. The Front Range peaks rise approximately 22,000 ft (6600 m) from the floor of the basin under Denver.

The deep part of the basin near Denver became filled with Tertiary sandstone and conglomerate, a layer now called the Denver Formation. In the regions to the north and south of Denver, however, increased stream erosion wore away the uppermost layers of sandstone, revealing the parts of the underlying Cretaceous Pierre Shale to form wide valleys along the South Platte and Arkansas rivers known as the Colorado Piedmont.

The unexposed shale within the basin itself forms a petroleum province with several large fields, including the Wattenberg Field northwest of Denver.

[edit] References

• Roadside Geology of Colorado, Halka Chronic, Mountain Press Publishing Company, Missoula, Montana (1980).