76 J. J. .stevp:xson — lower carboxiferous, Appalachian basin 



a thin sandstone at the bottom, with shales and limestones in the inter- 

 val. The limestones diminish southwardly. This valley terminates in 

 southwest Blount, nearly 100 miles farther north than the exposures in 

 Bibb county * 



Here one has reached the southern extremity of the eastern exposures ; 

 farther southward the Carboniferous is buried under the Cretaceous and. 

 later de]iosits, so that the final conditions in that direction can not be 

 ascertained. On the westerly side of the Plateau area exposures are 

 almost continuous in Alabama, the rocks forming a broad band across 

 the northwestern seven counties of the state and reaching a little way 

 over into Mississippi, the breadth of exposure being due to absence of dis- 

 turbance. The deep trenching by the Tennessee river near the northern 

 line of the state has removed the upper beds, so that north from that 

 river, in Madison, Limestone, and Lauderdale counties, one finds practi- 

 cally only the equivalents of the Fort Payne, while south from the river, 

 in Morgan, Lawrence, Franklin, and Colbert, only the equivalents of the 

 Bangor occur, underrunning the Coal Measures near the southern border 

 of the first three and the Cretaceous in the last. 



Western outcrops in Alabama. — Some deep valleys in western Jackson 

 (on the Tennessee line) reach the Bangor, which shows at from 160 to 

 200 feet from the to]i an apparently persistent sandstone, which is 

 probably the upper Hartselle, the limestone below^ it being cherty. In 

 Madison, just west from Jackson, both divisions are showMi full 3^ ; the 

 Bangor exhibits abrupt variations, being 200 feet in the northeastern 

 part of the county, but only 100 feet at a little way southeast from Hunts- 

 ville, while it is 200 feet at the Tennessee river in the southeastern corner 

 of the county, beyond which it passes under the Coal Measures. These 

 abrupt changes and the condition in western Jackson lend countenance 

 to the suggestion that the Dorans Cove sandstone of northeastern Jack- 

 son may be the upper Hartselle. The Hartselle in Madison is 150 to 

 225 feet thick, with a persistent sandstone on top and a thin flaggy sand- 

 stone at the bottom, the interval being filled mostly wdth more or less 

 cherty limestone. All of the sandstones decrease eastwardly, but the 

 upper one persists. In Morgan, south from Madison and west from 

 Blount, the Bangor is thicker, 400 to 425 feet, and portions are as cherty 

 as the Lauderdale, while the Hartselle is from 200 to 300 feet. The 

 sandstones of the latter are thin at the east, but thicken westwardly, the 

 upper bed becoming 100 feet, and the limestones are cherty everywhere- 

 The Bangor is slightly thicker in Lawrence, sometimes reaching 450 

 feet, while the Hartselle is 300 to 350 feet, the upper sandstone becom- 

 ing 150 feet and the bottom sandstone 15 feet. In Franklin, west from 



* Henry McCalley, vol. i, pp. 3U7, 309, 320, 360-367, 402, 407, 409, 410. 



