Griswold.] 478 [March 6, 
the iii;i|), the noccssjuy extension e:istw:u(l uikU'I- the Mississippi 
enibayinent of tlie folded l*ahieozoic rocks of Arkansas must have 
been an effective harrier to soutliward-flowino- drainage for some 
time aftei' the com})letion of the fohlinu;. It is true tliat the folds 
do not connect in an axial lino with those of the Ap[)alachians, 
but as tlie dips of the strata arc steej) where last seen before 
covered by the Cretaceous and later sediments, the system of 
folds must extend far before dying out ; indeed, the disturbances 
noted by llilgard^ in the Lower Carboniferous rocks of northeast 
Mississippi may indicate the extreme end of the system. Con- 
tinuing from northeast Mississippi the rocks of northern Alabama 
l)elong to the base of the Lower Carboniferous with the Silurian 
exposed in patches ; thus the line of uplift is continued, and it is 
not until northeastern Alabama is reached that a depression in 
the old line of disturbance is indicated by the occurrence of the 
Carboniferous series. In northeast Alabama, then, was the most 
l)robable outlet for southward-flowing drainage if' such existed in 
pre-Cretaceous times, but as the Cumberland River, regarded by 
Hayes and Campl)ell as antecedent in origin, now crosses this 
axis of depression farther to the north we may believe that no 
great river formerly held a southward course along it. 
tf then the lower Mississippi did not exist at the close of 
Palaeozoic time, when and how was its course gained? We may 
learn this by following the geographical history farther. The 
Cretaceous peneplain in Arkansas dips gently eastward and in 
Alabama westward beneath the sediments of the Mississippi 
embayment, and presumably the peneplain surface is continuous. 
But if there is here a buried peneplain there was formerly an 
old land mass subject to subaerial denudation, and this denu- 
dation continued from the close of Palaeozoic time into the Creta- 
ceous ; thus the land of the present region of the lower Missis- 
sippi was presumably above water during this time and would 
have remained a barrier to an escape of drainage from the north. 
1 Agriculture and geology of Mississippi, 18G0. On page 47 he states : " It is more 
difficult to ascertain the order of superposition of the several strata, because in 
dilferent localities they appear partly horizontal, partly at various inclinations to 
the horizon, in opposite directions." As he records no tliiis but to the north and 
south, ciist and west axes of deformation are indicated, thus corresponding with the 
Ai"kan§as system. 
