2096 ELIOT BLACKWELDER 
a gap embracing perhaps’ Algonkian-Modern. Assuming as correct 
the current view that the Piedmont at this point was submerged in 
the Ordovician’ period, but not later, we find that the time-value 
has also changed from 
tu o 
9 g > 
= : 5 Miocene- Modern to 
a ~ z dd 
«|, —, E aS Ordovician-Modern, a 
O]s = ts . 
2 2 ” ae 4 2 great and _ relatively 
a 
Bp abrupt change, but not 
s so great as that ob- 
o 
i 3 served in the hiatus. 
KL 8 5 Farther westward (D) 
|} s 
am 3 Eg submergence would 
° = . 
2 ri cause modern _ sedi- 
} vu fal . 
A “ a ments to be laid upon 
U 
‘|| 3 y g the truncated edges of 
' ‘ i 
| 3 2 i : 
t}| 3? S Z the Paleozoic strata in 
1 | ( Q 
\ | a | 2 the Appalachian Valley 
Wil | By = and Mountains. The 
I | ct | al . ° 
Kl E ) 7 discordance here is less, 
| — : 
UN Wfalistss lee | N== =e a although still great, and 
| % = a= re) fo) ) 
| Neil deca dane 5 the stratigraphic hiatus 
! 5) 
aia. has, decreasedsstom pene 
(yi) o) 5 . 
=H s = haps Ordovician. 
S! ° g 
ii = | Modem @hesreaion 
im: ae 7 
ict £8 is believed to have been 
rear e -4 S . 
‘6 & eroded ever since the 
WL 9 oO : 3 
a Bone Permian period, and 
il ¢= so the time-value is 
1 i S 
1 32) Permian Meodiemm 
i Sx 
| & ° 
| ~ .§ Now supposing the sub- 
‘| 3 8 mergence to lap over 
| 2 Alleg! 
4% upon the egheny 
ORT 
| i cE plateau (£), angular 
F | s discordance is quickly 
af. 5 © s 3 E 5 Q 2 
EE ae S § < z o> = 2 tN. H. Darton, Am. Jour. 
Tia! ° <= Oe} 9 . 
Beysess 5 SE > gb o- Sci, 3d series) Vola olen, 
proesaaeag <= | ze] 3 
' J! § = (1892), pp. 50-52. 
