The Mississippian-age Nada Member is a fossiliferous
shale found in the upper part of the Borden Formation in the
western-belt of outcrop in eastern Kentucky. It consists of shale with
interbeds of calcareous shale, and thin limestone and siltstone
stringers. The Nada overlies the massive Cowbell Siltstone Member of
the Borden and unconformably underlies the Renfro Member of
the Slade Formation, a predominantly limestone and dolostone unit. In
the southern part of the belt of outcrop, in Madison and Rockcastle
counties, Kentucky, the Nada is overlain by the thin interbedded
siltone and shale Wildie Member of the Borden. The Osagian-age Nada has
been cited as being equivalent to the uppermost Tournasian (Lee and
others, 2005, Work and Mason, 2009) in Europe. The Cowbell
Silstone has been interpreted as having been deposited as a subaqueous
delta known as the Borden Delta (Chaplin, 1980). The glauconite- and
phosphorite-bearing Nada is thought to have been deposited as part of a
transgressive-system tract on top of the Borden Delta platform.
Glauconitic siltstone [bar = 1cm]
Crinoidal
argillaceous limestone bed
Macrofauna
Identified macrofauna from the Nada Member include echinoderms,
mollusks, brachiopods, bryozoans, cnidarians, arthropods and
poriferans. Most abundant are bryozoans, brachiopods and echinoderms.
Dissassociated fossiliferous shales yield fines composed of about 95%
fenestrate bryozoan debris and 5% crinoid ossicles, other fossil
debris, pyrite, glauconite and phosphorite. Thin argillaceous limestone
beds contain abundant crinoid, brachiopod and fenestellid and ramose
bryozoan fossils. See the following categories for more information.
