--> ABSTRACT: Possible Flexural Mechanisms for Origins of Extensive, Ooid-Rich, Carbonate Environments, Middle and Early Late Mississippian, East-Central United States, by Frank R. Ettensohn; #91023 (1989)

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Possible Flexural Mechanisms for Origins of Extensive, Ooid-Rich, Carbonate Environments, Middle and Early Late Mississippian, East-Central United States

Frank R. Ettensohn

During the earliest Mississippian, much of east-central United States was a deep-water black-shale basin formed due to subsidence accompanying Acadian tectonism; by the middle Mississippian, this basin had been transformed into a very shallow epeiric sea characterized by ooid-rich carbonates. This transformation probably occurred in two parts due to flexural mechanisms accompanying the end of the Acadian orogeny and the beginning of the Ouachita orogeny.

In the eastern part of the basin, with the end of active Acadian deformational loading, lithospheric relaxation caused uplift and eastward migration of the Acadian peripheral bulge from near the Cincinnati arch into the Appalachian basin. By the middle Meramecian, this uplift and a concomitant infilling of the basin with post-orogenic clastics created an extensive shallow-water platform conducive to ooid deposition well into the Appalachian basin.

In western parts of the cratonic black-shale basin, from the western flanks of the Cincinnati arch to the eastern flanks of the Transcontinental arch, any infilling with postorogenic Acadian clastics was minor. However, by the Kinderhook-Osage transition, apparent collision and subduction leading to the Ouachita orogeny had begun, and with the inception of collision, the entire foreland as far north as the Illinois basin was upwarped by the cratonward (north and northeast) migration of the accompany peripheral bulge. As a result, by the early Meramecian, shallow-water conditions favorable for oolitic-carbonate deposition prevailed throughout the area.

Ooid deposition persisted locally on this large cratonic platform until the middle Chesterian when clastics, derived from rebounding terrains in the north and east and from rising Ouachita mountains to the south, began inundating the area.

AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.