FOSSIL COMMUNITIES OF THE BORDEN (MISSISSIPPIAN) DELTA IN INDIANA AND NORTHERN KENTUCKY

Abstract

dominated by crinoids and bryozoans. The carbonate bank was dominated by large brachiopods (Spirifer, Imbrexia) and camerate (Alloprosallocrinus) and disparid (Halysiocrinus) crinoids. The distributary channel was occupied by a variety of small, short-stemmed advanced inadunates (Abrotocrinus), and the interdistributary mudstones by a great variety of fenestrate (Fenestella) and cystoporate (Cheilotrypa) bryozoans, as well as crinoids and brachiopods. The delta slope community was generally not tiered and consisted primarily of large brachiopods (Orthotetes, Syringothyris) that could remain fixed in position on unstable slopes. The prodeltaic community included a variety of bryozoans (Rhombopora, Cystodictya) and crinoids (Halysiocrinus, Synbathocrinus) as well as gastropods and pelecypods (Bembexia, Phestia, Ctenodonta). The slope community originated by migration down from the platform by some species and up from the prodelta by others. Species diversity at individual sites on the delta platform range from 47 to 155, on the slope from 2 to 23, and on the prodelta from 35 to 103.