184 RECORD OF DEEP- WELL DRILLING FOR 1905. 
So far as the evidence warrants, the various logs show the geologic 
age of the beds and formations penetrated. In the choice of forma- 
tion names the usage of the Survey is followed. Some local or State 
names will no doubt be missed, owing to the substitution of place 
names for the older descriptive names, which, however apt for the for- 
mation at the place where first bestowed, may be absolutely mislead- 
ing if applied to beds of the same age not far distant. The above 
table shows the stratigraphic divisions (formations, groups, series, and 
systems) used in classifying the sedimentary rocks in certain parts ot 
the United States. 
The term formation, as here used, means any rock or succession of 
rocks having such extent and such peculiarities that it can be distin- 
guished over a considerable tract of country and treated as a unit in 
mapping. Thus a formation may be a persistent bed but a foot or 
two thick, or it may be a succession of beds 10,000 feet thick. With 
the progress of investigation the number of formation names has 
become great. The list is continually increasing, though some names 
are replaced by others as accumulating evidence shows that certain 
names are entitled to preference. Also, since a limestone bed in one 
locality may have been deposited at the same time as a sandstone bed. 
in another and since the succession of changes of deposition may have 
differed widely, a formation in one locality may represent half a dozen 
in another. Hence a table of formation and group names (several 
formations make a group) for the whole county would be long and 
complicated. 
ALABAMA. 
L3. Well near Hazelgreen, Madison County. 
[Well begun and completed in 1905. Authority, II. B. Conover, driller. Geologic correlations by 
E. O. Ulrich] 
The red clay at and near surface has resulted from the decay of the underlying limestonfl 
(the Tullahoma), which is of Mississippian age. The underlying shales and limestones, in 
downward order, are Chattanooga shale (Devonian), Helderberg limestone and shale 
(Silurian), Fernvale limestone and shale (Ordovician), Leipers limestone and shale (Ordo- 
vician), "Trenton" limestone (Ordovician). These formations were determined by care- 
ful study of the fossils found in their outcrops. The well drillings show few marked differ- 
ences below the Chattanooga shale, the only striking formation being the Fernvale red 
limestone and shale. 
Record of well on D. A. Moseley farm, in the SW. \ NW. \, sec. 19, T. 1, R. 1. 
Tullahoma: Feet. 
Red clay 0-20 
Clay and rock 20- 67 
Hard gray flinty limestone 67- 93' 
Chattanooga: 
Hard black shale 93-103 
