128 J. F. Fitzpatrick, Jr. 



associated with the centers proposed for cambarine, cambaroid, orco- 

 nectoid, graciloid, and mexicanoid stock emergences (Hobbs 1981, 

 1984). 



Although the exact routes followed in the past by waters now flow- 

 ing in the Tennessee River do not meet with general agreements among 

 geologists, their paths at specific times are critical to interpretations of 

 crawfish evolution. Hobbs argued (1981:52-53) that the invasion of fresh 

 waters by the cambarine stock occurred in late Cretaceous or early 

 Cenozoic times. He placed them spatially in the tidewater areas of the 

 extreme Southeast. Thus, the route(s) of major watercourses from the 

 southern Appalachians becomes very significant in interpreting the 

 invasion of North America. It is important, too, to recognize that use of 

 the word "river" here designates a basin or drainage source. Rivers 

 themselves have lives measured in thousands of years, not the millions 

 of geologic times. 



Some geologists (Hayes and Campbell 1894, Hayes 1899) believed 

 that the Appalachian segment of the Tennessee River flowed south- 

 westward through the present Coosa-Alabama basin (or the Black War- 

 rior). They envisioned a capture near Chattanooga at the close of the 

 Tertiary, which led to the present transection of the Walden Ridge. 

 Zoogeographically, this would seem to be supported. A major faunal 

 break seems to be associated with the Walden Gorge. 



Some geologists (Johnson 1905, Wright 1936) believed otherwise. 

 They insisted that the present route of the Tennessee River has existed 

 at least since the Schooley (dissection of the peneplain ending probably 

 in the Miocene). The geological evidence to support this thesis is of 

 equal strength as that supporting the one of Hayes and some subsequent 

 authors. The Tennessee remains a difficult problem. A good review is in 

 Thornbury (1965:124-126). 



Sedimentary analysis of Mississippi "Eocene" deposits by Grim 

 (1936), however, provided compelling data to indicate the delta of a 

 sizeable river in eastcentral Mississippi. The Midway alluvial deposits 

 (Paleocene) (Fig. 3) indicate that a significant river had a delta in the 

 vicinity of the Chickasaw-Clay counties area near the juncture of the 

 Porter's Creek and Clayton formations. The succeeding Wilcox deposits 

 (early Eocene) (Fig. 4) demonstrate the continuance of this river into the 

 Choctaw-Montgomery- Webster counties area. Grim (p. 208) attributed 

 both the Midway and Wilcox deposits to a "complex of ancient rocks 

 located in the present Piedmont Plateau." The Claiborne deposits (mid- 

 Eocene), in contrast, suggest that "many streams" (p. 214) rather than 

 one contributed to them. Similarly, the post-Claiborne Jackson Forma- 

 tion (late Eocene) indicates the major "Appalachian [= Tennessee] 

 River" was not a controlling depositional factor in Mississippi. 



Brown (1967) was concerned over an apparent inconsistency of the 

 major streams of southern Mississippi. Contrary to other Recent drain- 

 age patterns, they flow at a decided angle to the dip and strike of the 



