IB. TENNESSEE VALLEY. 41 



Paleozoic rocks are overlaid by unconsolidated coastal 

 plain strata, whose boundaries are not easily defined. 

 The soils of the valley are various, but red and calcare- 

 ous clays and loams above the average in fertility pre- 

 dominate in the central portion, with more limestone out- 

 crops eastward and cherty soils westward. Sand is 

 rather scarce. 



Topography and hydrography. — Brown's Valley, which 

 the Tennessee River follows from the northeastern cor- 

 ner of the state to Guntersville, contains several low 

 longitudinal chert ridges. The country bordering the 

 river from about the eastern edge of Morgan County to 

 the western edge of Limestone is a wide base-leveled 

 undulating plain (not a flood-plain, however), in which 

 some of the roads and railroads run straight for miles. 

 Toward its eastern end there are several peaks and 

 small plateaus rising above it, capped by sandstone be- 

 longing to the next region, which protects the underly- 

 ing softer limestone from erosion and to a considerable 

 extent from solution by meteoric waters. A few of the 

 smaller peaks near Huntsville have alreadj'^ lost their 

 sandstone caps, and are therefore much farther on the 

 road to complete obliteration than those which are still 

 capped. 



In Lauderdale and Colbert Counties there are many 

 chert ridges and limestone (Tuscumbia or St. Louis 

 limestone) bluffs near the river. The Bangor limestone 

 is almost confined to the steep slopes connecting this val- 

 ley with the sandstone plateau region to be described 

 next, and it is especially noticeable in Jackson County 

 and the eastern part of Madison, where the edges of the 

 plateau have been much dissected by erosion. A promi- 

 nent feature of Morgan, Lawrence and Colbert Counties 

 is the Little Mountains, an escarpment running approxi- 

 mately east and west, with a steep northern slope rising 

 300 to 500 feet above the main valley (or 900 to 1,000 

 feet above sea-level), and a gentle southern slope. This 

 escarpment owes its presence to the Hartselle* sandstone 

 above mentioned. 



♦Misspelled "Hartsells" by the U. S. Post Office Dept. 



