•  
  •  
 

Abstract

The Lower Mississippian Boone Formation is a chert-bearing, fossiliferous limestone typically 100-115m. thick forming the Springfield Plateau across the tri-state region of northwestern Arkansas, southwestern Missouri, and northeastern Oklahoma. The Boone represents the maximum flooding, highstand, and regressive intervals of a single, third order transgressive-regressive carbonate cycle bounded by regional unconformities. Two types of chert occur in this formation, and provide the basis for subdivision of the Boone into informal lower and upper members in northern Arkansas. The lower Boone represents early Osagean maximum flooding conditions and consists of calcisiltites with interbedded dark, nodular chert. This chert exhibits compaction phenomena and shrinkage fractures, indicating a penecontemporaneous origin from reorganization of silica immediately below the sediment water interface prior to lithification of the carbonate sediments (Manger et al. 1988a). The upper Boone represents late Osagean highstand and regression and consists primarily of carbonate grainstones and packstones (Shelby 1986). This interval contains white, later diagenetic chert, interpreted as a groundwater phenomenon in which silica has replaced lithified carbonate along its bedding planes, replicating the fabric of the limestone (Manger and Shelby 2000). This later diagenetic chert replacement favors the finer grained intervals and replicates the fabric of the limestone being replaced. Previous studies have shown that the penecontemporaneous chert typically comprises 40-50% of the lower Boone interval, while the later diagenetic chert contribution to the upper Boone ranges from 30-95% (Liner 1979). Understanding chert development is unsettled, and has been the subject of debate, primarily involving the source of the silica producing the chert, and the mode of formation of the chert-bearing intervals. Geochemical analyses suggest a volcanic rather than biogenic source for the silica in the Boone Formation.

Download

Share

COinS