134 J. F. Fitzpatrick, Jr. 



It appears, then, that there is considerable evidence to counterindi- 

 cate Smith- Vaniz's (1968:122-124) contention that the present zoogeo- 

 graphic pattern of aquatics (specifically Alabama fishes) must be inter- 

 preted on the basis of the Tennessee occupying its present course at least 

 since Cretaceous times. The only question seems to be when did the 

 connection of the upper Tennessee directly into the Gulf of Mexico 

 become replaced by the indirect Ohio River outlet. Isphording (1981) 

 claimed Miocene or early Pliocene; May (1981) argued Miocene; and 

 Brown (1967) and Murphey and Grissinger (1981) said Pliocene. Grim's 

 Eocene datings (1936) seem possibly compromised, but his stratigraphic 

 relationships remain valid. 



Equally, one must recognize that nothing in the geologic record 

 requires continuous discharge through a particular basin, and intermit- 

 tent flow remains a viable hypothesis. Indeed, Grim's interpretation of 

 Claiborne sediments seems to indicate this. A river could easily have 

 accounted for Grim's deposits, found another outlet during late Eocene, 

 and reestablished a direct Gulf outlet during Miocene times. It is gener- 

 ally recognized that Miocene is the date of a significant uplift of eastern 

 North America. Even the Citronelle Formation in southern Alabama 

 exhibits a "tilt" to reflect the magnitude of this change (Isphording, 

 pers. comm.). Isphording and Flowers (1980) reexamined the Citronelle 

 in Alabama and Mississippi and suggested that it represents the rework- 

 ing, largely as a result of this uplift, of older deposits. And regardless of 

 precise interpretations, the Miocene uplift surely had profound effects 

 on the directions and flow rates of the then-extant watercourses. Equally, 

 the uplift would have had significant impact on the nature of the gravels 

 and patterns of their deposition. 



Alt's (1974) opinions on drainages and the Miocene in general were 

 given considerable weight when Hobbs (1981) speculated about phylo- 

 geny. In reviewing the development of the Cambaridae, Hobbs over- 

 looked, possibly deliberately, an important part of Alt's thesis: an arid 

 Miocene. An arid climate would reduce flow of streams and promote 

 emergence of forms adapted to lentic situations. Contrarily, however, 

 the same climate would impede dispersal of crawfishes still adapted to 

 lotic situations. Reduced stream flow would produce a saline intrusion 

 into estuaries. Procambarus (Ortmannicus) acutus acutus (Girard) and 

 P. {Scapulicambarus) clarkii (Girard) are among the very few species 

 with any saline tolerances; thus, the dispersal of cambarines would be 

 effectively blocked in tidewater areas. The overland route would like- 

 wise be impaired, leaving only stream capture as a mechanism for invad- 

 ing new river systems. 



Fortunately, however, Alt's thesis can be seriously questioned. 

 Isphording (1970) noted that epidote, garnet, and hornblende, although 

 present only a short distance away, are absent from the Kirkwood For- 

 mation and Cohansey Sand of the Middle and Upper Miocene in New 

 Jersey. Otherwise, he found that the remaining heavy mineral species, 



