219] E. W. Berry 21 



accompanying sketch map, is roughly lunate in outline with 

 the southeastern horn terminating near Montgomery, Ala- 

 bama, and the other extending as an attenuated band across 

 western Tennessee. As will be seen, the greatest width of 

 outcrop coincides with the maximum thickness of sediments 

 in a belt about 125 miles in length which is at right angles 

 to the axis of the Appalachian land mass. To the northward 

 the deposits become thinner, are prevailingly gravels and are 

 shown by the fossil plants to be somewhat younger than the 

 main body of the deposits. 



In the interpretation of the Tuscaloosa deposits with their 

 gravels and compound oblique cross-bedded sands, their occa- 

 sional traces of glauconite and their abundance of driftwood, 

 one cannot fail to be impressed with their delta-like character. 

 We are now fairly familiar with the main features of delta 

 deposits in different parts of the world 3 and Grabau 4 and 

 Barrell 5 have recently contributed considerable toward the 

 interpretation of Paleozoic delta deposits. Eeturning for a 

 moment to the physiographic history of the Tuscaloosa region 

 we find that there are no sediments later than Pottsville age 

 until the deposition of the Tuscaloosa in the earlier Upper 

 Cretaceous. This long interval resulted in the nearly com- 

 plete baselevel known as the Cumberland peneplain. There 

 must have been some regional uplift or warping at the begin- 

 ning of Tuscaloosa time to account for the sudden augmenta- 

 tion in river action and the inauguration of the large delta 

 or series of deltas along the southwestern margin of the land 

 mass. There is no evidence in the sediments that an Appa- 

 lachian river flower southwestward through the Coosa valley. 

 This would also have brought the bulk of the sediments far- 

 ther eastward than where they now occur. While I regard 

 Johnson's evidence (op. cit.) as conclusive for the course of 



3 Credner, H., " Die Delten," Petermann Geog. Mitth., Erganzungs- 

 heft 56, pp. 1-74, pi. 3, 1878. 



4 Grabau, A. W., Early Paleozoic Delta Deposits of North Amer- 

 ica," Bull. Geol. Soc. Am., vol. 24, pp. 399-528, 113. 



B Barrell, J., idem., vol. 23, pp. 377-446, 1912. 



