No. 1621. LATE NIAGARAN STRATA—PATE AND BASSLER. 41% 
POST-DIXON FORMATIONS. 
Along the western flank of the Cincinnati axis the Silurian rocks 
following the Waldron shale are known as the Louisville limestone. 
In West Tennessee the same interval is occupied by several limestone 
and shale formations which have been named by Foerste, in ascend- 
ing order, the Lego limestone, Dixon bed, Brownsport bed, and Gant 
bed. The Brownsport and Gant beds are the special subjects of this 
paper. 
‘ The term Brownsport was loosely defined. In fact, the name could 
hardly be considered as defined at all, since practically the only de- 
scription of these strata given by the author of the name is to the 
effect that the name Brownsport bed is applied to the richly fossil- 
iferous section overlying the Dixon red clay and containing the fauna 
studied by Roemer during his visit to Decatur County, Tennessee. 
In this sense the name would have reference mainly to the crinoid, 
brachiopod, and coral beds, so conspicuously shown in the section at 
Brownsport Furnace. Apparently the name was instituted only for 
convenience of reference, and not as a formational name. In the 
same article (p. 576) rocks now known to be equivalent to the brachi- 
opod: beds of the Brownsport Furnace section are named the Gant 
bed. The recognition of either or both of these names as formations 
is thus made questionable, and we were in doubt whether (1) to ap- 
ply the name Brownsport as a group term to the post-Dixon Niag- 
aran strata as exposed at Brownsport Furnace, (2) to extend the term 
so as to include all the Niagaran rocks following the Dixon, or (3) to 
restrict and redefine the formation entirely. After a consideration 
of all the sections, the first course seemed the wisest. 
In the post-Dixon Niagaran interval four well-marked divisions 
can, we believe, be recognized. The lowest is a series of rather 
widely distributed, very fossiliferous white clays and thin-bedded 
limestones furnishing most of the crinoids afforded by the glades; 
argillaceous limestones and shales, quite similar lithologically to the 
Dixon but of more local distribution, succeed these white strata, and 
are overlaid in turn by blue shales bearing great numbers of brachio- 
pods; just above the brachiopod beds are blue shales and cherty lime- 
stones in which the great coral fauna so well developed at Louisville, 
Kentucky, is likewise abundantly represented. In exposures of these 
strata in Tennessee the corals are sometimes so numerous that the 
ground is entirely hidden by the specimens. These three formations 
constitute the Brownsport group as here recognized. Finally, the 
Niagaran of West Tennessee is closed by a massive white, coarsely 
crystalline limestone, 70 or more feet thick, which seems to be of con- 
siderable extent, especially in the northern half of the area. 
e 
