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The AAPG/Datapages Combined Publications Database

Oklahoma City Geological Society

Abstract


The Shale Shaker
Vol. 63 (2013), No. 4. (January/February), Pages 254-273

Composition and Classification of Mississippian Carbonate Mounds in the Ozark Region, North America

Morgan Unrast

Abstract

Mississippian crinoidal-bryozoan carbonate mounds in the Compton and Pierson Limestones, St. Joe Group, have been called Waulsortian or Waulsortian-type. Waulsortian mounds contain features such as polymuds, radial fibrous calcite cement filled cavities and specific grain-type assemblages (Lees and Miller, 1995). However, these features are rare to absent in Ozark mounds. This study classifies the Ozark mounds and determines their depositional setting and diagenetic history.

Ozark mounds occur as knoll-form build-ups, may display minor stacking and have a strong lateral component. The Compton mounds in Missouri are interpreted to have formed in calm and moderate to deep water, whereas Pierson mounds are interpreted to have formed at shallower depths as evidenced by more abraded skeletal fragments and a lower percentage of mud. Both Ozark mounds have a similar diagenetic history. Compton mounds are bryozoan-rich, mud-dominated mounds while Pierson mounds are crinoid-rich and grain-dominated. Statistically, the two types of Ozark mounds differ in the abundance of skeletal fragments and mud. Overall, the Compton and the Pierson mounds in Benton County, Arkansas are classified as Waulsortian-type and lime mud accumulation bioherms (Wilson, 1975). The grain-rich Delaware County Pierson mounds are classified as minimally transported bioaccumulation mounds due to their bedded mound-core facies, which are transported accumulations of skeletal fragments.


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