Absaroka sequence

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The Absaroka sequence was a cratonic sequence that extended from the end of the Mississippian through the Permian periods. It is the unconformity between this sequence and the preceding Kaskaskia that divides the Carboniferous into the Mississippian and Pennsylvanian periods in North America.

Like the Kaskaskia sequence, Absaroka sedimentary deposits were dominated by detrital or siliclastic rocks. The first sediments were deposited near the continental margins, particularly near the Ouachita and Appalachian highlands. Characteristic of the strata from this time are cyclothems: alternating marine and non-marine strata indicative of changes in sea-level, probably due to cyclic glaciation in the Southern Hemisphere.

In North America, the waters of the Absaroka sequence regressed westward as the highlands to the east steadily eroded. Restricted oceanic circulation in the west led to extensive evaporite formation. By the end of the period, the regression was complete, and the marine strata were superseded by extensive red bed deposition.

[edit] Reference

  • Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont: West Publishing Company, 1997. ISBN 0-314-09577-2(pp. 544-9)


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