20 PLANT LIFE OF ALABAMA. 
the latter rocks, decomposed and converted én sé¢w into stratified clays, 
form the deep, warm soil of a region noted for its fertility. 
The metamorphic region extends without any interruption from the 
central belt of sands and gravels along the eastern border of the State 
nearly to its northern boundary. 
REGION OF THE COAL MEASURES. 
The largest portion of the northern part of the State is occupied by 
the Coal Measures. There are three coal fields recognized, more or 
less separated by other formations which will be presently referred to. 
The most southern of these fields is the Cahaba coal field, beginning 
above the shoals of the Cahaba River. This field is separated from 
the Warrior field by the Birmingham or Jones Valley toward the 
northwest, and from the Coosa coal field by the Cahaba Valley toward 
the southeast. The southern outlines of this region are extremely 
broken; the strata of the steep rugged hills disturbed hy many folds 
and faults are deeply furrowed by erosion. The principal part of this 
region is formed by the Warrior coalfield, a triangular area, with the 
southern corner at the shoals of the Warrior near Tuscaloosa. The 
topographical features of the western field are of much greater uni- 
formity than those of the Cahaba field. In the lower part of the 
basin proper, where soft shales overlie the lower conglomerate of the 
Coal Measures, the surface is undulating, the highest swells rising 
most frequently to low hills. Toward the north the hills pass gradu- 
ally into the table-lands formed by the heavy bedded sandstones of 
the upper conglomerate, which exhibit an almost horizontal stratifica- 
tion. These table-lands are the flattened summits of the several con- 
verging spurs of the Appalachian chain, known north of the Tennessee 
River as the Cumberland Mountains and south of the river as the 
Sand Mountains; the latter with escarpments fronting the Tennesseé 
Valley toward the north, and toward the southeast, Blounts Valley, 
which is formed by the southern extension of the Sequatchee fold. 
The table-land lying between Blounts Valley and Big Wills Valley 
in the southeast is known as the Raccoon. Mountain. The table-land 
of the range forming the eastern border of Big Wills Valley is known 
as Lookout Mountain, the steep escarpment of which fronts the Coosa 
Valley. 
This highland area of the Coal Measures presents in its general 
aspect a somewhat rolling plateau. It rises to an elevation of from 
1,000 to a little over 2,000 feet above the adjacent valleys. It slopes 
gently away from the greatest elevations in the north to the north- 
western limits of the region, where the Coal Measures disappear under 
the deposits of more recent formations; and to the south, where it 
passes gradually into the lower hills in the Warrior coal basin proper. 
