132 J. F. Fitzpatrick, Jr. 



interpretations of the implications of the materials that compose them, 

 and clearer understandings of the events and periods of deposition. No 

 longer is the zoogeographer able to rely on a few well-established stud- 

 ies and assume a stability of concept. As the geologic knowledge pro- 4 

 gresses, so the zoogeographic interpretations must follow. And signifi- 

 cant modification of age, stratigraphic relationships, sources of deposits, 

 and biological responses is to be expected as the essentially unfossilifer- 

 ous elastics of the Gulf Coastal alluvia are examined. 



Isphording (1981), working with drill cores from southwestern Mis- 

 sissippi and especially in the Hattiesburg Formation (Miocene), amassed 

 considerable, nearly irrefutable mineralogical data establishing the 

 existence in Miocene times of a river that entered the Gulf somewhere 

 near Hattiesburg (Fig. 6). Further, these data tie the sediments to the 

 eastern Piedmont and southern Appalachians rather than to the "local" 

 source areas (Isphording 1983). The mineralogical suites encountered 

 are incompatible with weathering from the Mississippi Embayment to 

 the north of the collecting sites or the more remote Rocky Mountains or 

 Central Interior, which had been suggested as sources of the alluvium of 

 the central Embayment by earlier writers (Storm 1945, Murray 1955, 

 MacNeil 1966). Such a river, if not the Tennessee, requires the discovery 

 of yet another river of equal magnitude draining from the same Appa- 

 lachian source area. No geological evidence exists to support such a 

 thesis. Even more data are available to support the contribution of the 

 southern Appalachians to the Embayment. Todd and Folk (1957), 

 working with sediments from Bastrop County, Texas (lower Claiborne), 

 reported that they encountered a kyanite-saurolite suite that they felt 

 could come only from the southern Appalachians, which suite they 

 called "diagnostic" (p. 2560). 



Isphording (1981) and Brown (1967) implied that the "Eocene" 

 deposits of Grim (1936) were possibly misleading in dating the demise of 

 the last Tennessee outlet directly into the Gulf. Working with geophysi- 

 cal logs and elastics, subsurface and surface, and mapped outcrop pat- 

 terns, May (1981:29) independently reached the same conclusions: 

 "Miocene outcrop patterns should be extended further landward into 

 the Embayment," in Mississippi. Analyses from drillings in northcentral 

 Mississippi led Murphey and Grissinger (1981) to believe that the mate- 

 rials under the Pleistocene loess mantle as far south as Holmes County 

 suggest an erosion surface, frequently out of phase with modern sur- 

 faces. They placed the age, from paleomagnetic data, at earlier than 

 700,000 B.P. (late Pliocene-early Pleistocene) and postulated a general 

 "Citronelle" age for these deposits. None of these hypotheses seems to 

 be incompatible with Alt's (1974) ideas that modern stream drainage 

 patterns (on the Atlantic coast) began in post-Miocene times. But Mur- 

 phey and Grissinger's (1981) conclusions indicated clearly that modern 

 drainage patterns in the upper Embayment are unreliable indicators of 

 history before the late Pleistocene. 



