Origin and composition of carbonate buildups and associated facies in the Fort Payne Formation (Lower Mississippian, south-central Kentucky): An integrated sedimentologic and paleoecologic analysis

摘要

An integrated sedimentologic, paleoecologic, and taphonomic analysis is used to test competing hypotheses for the origin of the Fort Payne Formation of south-central Kentucky. Characteristics of eight distinct facies, both carbonate and siliciclastic, support the hypothesis that the Lower Mississippian Fort Payne Formation is a progradational, shallowing-upward, basin-filling sequence. Five facies are considered in detail, including the autochthonous fossitiferous green shale facies; two autochthonous carbonate facies, wackestone buildups and crinoidal packstone buildups; and two transported carbonate facies, channelform packstone facies and sheetlike packstone facies. The two types of carbonate buildups are independent features, but both developed on mounds of green fossiliferous shale. The Fort Payne wackestone buildups are interpreted to be Waulsortian buildups. The Fort Payne Waulsortian and associated facies were deposited in the lower portion of the photic zone, which is phase D, the shallowest phase, of the Lees and others (1985) Waulsortian model. The source of carbonate mud in the buildups must have been autochthonous. All autochthonous facies had distinct faunas dominated by crinoids and bryozoans. The channelform and sheetlike packstone facies are interpreted to be proximal and distal portions, respectively, of carbonate apron deposits. Both are composed principally of crinoid packstones and represent deeper water portions of the Fort Payne basin-filling sequence. The siltstone facies records background sedimentation.