Deflation Origin of Mississippian Carbonate Eolianites, Southwestern Kansas, U.S.A.
F.E. (Rick) Abegg, C. Robertson Handford, 2001. "Deflation Origin of Mississippian Carbonate Eolianites, Southwestern Kansas, U.S.A.", Modern and Ancient Carbonate Eolianites: Sedimentology, Sequence Stratigraphy, and Diagenesis, F. E. (Rick) Abegg, David B. Loope, Paul M. (Mitch) Harris
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Upper Mississippian carbonate eolianites in the subsurface of southwestern Kansas formed by deflation of underlying subaerially exposed carbonates and/or inland migration of coastal dunes. Subaerial exposure and deflation resulted from a relative sea-level fall, as indicated by an abrupt basinward shift of lithofacies at the base of the carbonate eoliarutes. These carbonate eolianites rest directly on subtidal carbonates, such as skeletal wackestones; beach or tidal-flat strata are absent in all observed locations. Further evidence for deflation includes broken and abraded ooids, rounded syntaxial overgrowths on echinoderms, and lithoclasts. Detrital quartz, typically 5 to 30 percent volumetrically, is interpreted as mixing of deflationary carbonates with a continental source of siliciclastics, inasmuch as siliciclastic sand is rare in most subtidal deposits.
A model for the origin of deflation-sourced carbonate eolianites involves three stages: deflation, deposition, and stabilization. The deflation surface occurs at the basal contacts of the eolian limestones, where a poorly developed calcrete is locally overlain by a conglomerate that contains clasts of the underlying subtidal lithofacies. Deposition of deflation-sourced carbonate eolianites occurred during continued regression that exposed a large area to deflation and lowered the water table to allow for a greater depth of deflation. Stabilization of carbonate eolianites occurs when grains most easily deflated had been redeposited by winds or upon base-level rise. Transgression reduces the area for deflation and cuts off sedimentary pathways, and it also raises the water table, which both limits the depth of deflation and promotes growth of vegetation.
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Carbonate eolianites had long been considered to be limited to the Quaternary, but a number of Mesozoic and Paleozoic examples have been documented in the past 15 years. Thus, an increased awareness of carbonate eolianites is required to properly interpret the rock record and to assess their spatial and temporal distribution. The papers of this volume will help geologists to: (1) recognize carbonate eolianites and understand their preservation potential—recognitional criteria for most carbonate environments are common knowledge, but this is less true for carbonate eolianites; (2) understand their sedimentologic and diagenetic variability—diagenesis of carbonate eolianites has important economic considerations. Whereas Quaternary eolian limestones are commonly porous, Paleozoic and Mesozoic examples are typically tight owing to compaction; (3) understand the Psilionichnus (marginal marine) and Scoyenia (nonmarine) Ichnofacies—carbonate eolianites are not devoid of trace fossils; (4) interpret them in a sequence stratigraphic framework—interpretations of relative sea level during eolian deposition can be difficult, as differences between transgressive, regressive, and deflationsourced eolianites are subtle. Thus, the placement of sequence boundaries within interbedded eolian and subtidal carbonate successions is not entirely straightforward.