Print this pageA distinctive argillaceous wacke-packstone unit is present within the repetitious sequence of essentially identical sub-tidal to supratidal facies units that comprise the m- to 10s of m-thick Bangor Limestone parasequences. In northcentral Tennessee this unit is a 2.5 m-thick, very thickly bedded to "massive", burrowed to bioturbated, argillaceous wacke- and packstone. In southcentral Tennessee and northcentral Alabama it thickens to 9 meters and consists of decimeterthick, argillaceous, silty, wacke- and packstone interbedded with centimeter-thick, calcareous, silty, claystone. At its southernmost occurrence in northcentral Alabama, it is a 3.5 m-thick sequence of interbedded, decimeter-thick, skeletal grainstone tempestites and extremely fossiliferous, silty shale. It has a higher conodont content, 33-125 elements/kg, than that of the repetitious facies units, < 15 elements/kg. This content decreases from 125 elements/kg at the southernmost occurrence to 33 elements/kg at the northernmost.
The facies and conodont content of this unique Bangor unit strongly suggest that it is indeed a condensed interval with the amount of stratigraphic condensation increasing to the south. Because this unit is not present in northernmost Tennessee, this transgression terminated in southern Kentucky. It can be used to divide the Bangor Limestone into a lower transgressive systems tract, that thins to the north, and an upper highstand. The high-stand Bangor has a progradational facies relationship with the Pennington Shale of central Tennessee and northeast Alabama.
AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana