ABSTRACT: Mississippian Carbonate Eolianites in Southwestern Kansas

C. Robertson Handford

Prior investigations of Mississippian St. Louis and Ste. Genevieve limestones in southwestern Kansas have suggested deposition in subtidal grain shoals. However, abundant evidence for deposition in coastal eolian-dune systems has recently been uncovered. Mississippian cross-bedded eolianites, up to 30 ft thick, consist of well-sorted and fine-grained peloid-ooid, skeletal grainstones. Crossbed sets average about 1-3 ft thick but some reach 9 ft thick. Foreset laminae, averaging 16° and rarely exceeding 20° inclination, were created by grainfall rather than grainflow processes. Thin pinstripe bedding with inversely graded grains is abundant and interpreted as subcritically climbing wind-ripple cross-stratification. Worn cortex laminae of ooids suggest that abrasi n occurred outside the marine environment; marine ooids were washed and blown from shorefaces into coastal dunes where abrasion took place by eolian transport. The brecciated top of an eolianite unit with fissures filled by geopetal sediment probably represents a pedogenically weathered surface or near-surface crust of weakly cemented eolian dune sand. The eolianites and interbedded fine-grained sandstones, of wadi-interdune origin, contain laminated micrite layers and clasts, interpreted as paleocaliche crusts and fragments. Concentrically laminated micrite surrounding tubular cavities filled with sparry calcite are similar to root structures in Holocene-Pleistocene carbonate eolianites from Yucatan and the Bahamas.

This discovery of Mississippian carbonate eolianites in southwestern Kansas and 800 mi to the east in Indiana indicates that eolian carbonates are more common in the rock record than previously assumed and that conditions favorable for their development in North America were a hallmark of the late Mississippian.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990