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Laramide (Late Cretaceous-Early Tertiary) Orogeny in the Southern Rocky Mountains

1975; Geological Society of America; Linguagem: Inglês

10.1130/mem144-p1

0072-1069

Ogden Tweto,

Geology and Paleoclimatology Research

At the beginning of Laramide orogeny, a blanket of undisturbed Cretaceous and minor older Mesozoic sedimentary rocks 1,500 to 3,000 m thick covered the Southern Rocky Mountain province, and the last of a series of Cretaceous seas was starting to withdraw northeastward across the region. Beneath the blanket was an older and inhomogeneous terrane that in some places consisted of the eroded stumps of late Paleozoic mountain ranges made up of Precambrian rocks, and in other places of piles of sedimentary rocks thousands of meters thick on the sites of late Paleozoic basins. At the onset of Laramide orogeny in Late Cretaceous time, most of the buried mountain ranges were re-elevated, and adjoining Laramide basins, in part inherited from the late Paleozoic basins, began to subside and receive orogenic sediments. In addition, two anticlines of mountain-range proportions—the Sawatch and Uinta—rose from the sites of late Paleozoic basins.