Mabch 30, 1906.] 



SCIENCE. 



487 



signed to the Grand Gulf is between the 

 Vicksburg and the Chattahoochee lime- 

 stones; or between the members of the 

 Chattahoochee River series; or else as be- 

 ing equivalent to the whole of the above 

 series. 



We ought, if this assignment be correct, 

 to find it somewhere or other underlying 

 some of the Post- Vicksburg Tertiary rocks. 

 It has never yet, so far as the records show, 

 been seen in these relations. 



That it does not come in between the 

 Vicksburg and Chattahoochee is amply 

 proven by the observations of Professors 

 Pumpelly, Foerste, MeCallie, Burns, Dall 

 and others who have described the contact 

 of these formations in southwestern Georgia 

 and in Florida, with no sign of anything 

 that could possibly be referred to the 

 Grand Gulf coming in between them. 



Characteristic Grand Gulf beds were 

 observed by Mr. S. W. MeCallie and my- 

 self in 1904, on Withlacoochee River in 

 Lowndes County, Ga., near the Florida 

 line, overlying limestones holding Miocene 

 corals referred to the Chattahoochee hori- 

 zon, this limestone in its turn resting on 

 the Vicksburg; and I can personally bear 

 witness to the fact that the Grand Gulf 

 overlies the Miocene limestone at old 

 Chattahoochee Landing, and along the road 

 from Chattahoochee town to River Junc- 

 tion. From Chattahoochee Landing down 

 to Alum Bluff, the succession of Marine 

 Tertiarj^ beds along the river is unbroken; 

 in the words of Professor Dall, 'While the 

 series is not complete in any single section, 

 taken collectively there is no gap outstand- 

 ing between the beds, and, humanly speak- 

 ing, no room for misapprehension as to 

 their position and age."* Certainly no 

 Grand Gulf beds form any part of this 

 Chattahoochee River section, which ranges 

 from upper Oligocene, according to the 

 latest decision of Professor Dall, up to the 



'Bulletin Geol. Soc. Amer., Vol. 5, p. 162. 



Chesapeake Miocene of the Alum Bluff ex- 

 posure; but they do overlie in turn each 

 member of this series. 



But we have also seen above that east- 

 ■Hard of Escambia County, Ala., the Grand 

 Gulf beds are to be found overlying strata 

 older than the Vicksburg, e. g., the Clai- 

 borne, the Buhrstone, the Lignitic, the 

 Clayton and even the Ripley of the Cre- 

 taceous. It has not occurred to any one 

 to assign to the Grand Gulf an age older 

 than that first referred to, because of its 

 resting directly upon any of these sub- 

 Vicksburg formations. 



By way of parenthesis I might here say 

 that this transgression of the Grand Gulf 

 over the older formations in the eastern 

 part of Alabama, fiinds a kind of parallel 

 on the St. Stephens limestone. We have 

 recently identified isolated patches of this 

 limestone so far out of its usual position 

 as to be directly in contact with the Nana- 

 falia beds of the Lignitic and upon the 

 very verge of the Clayton. This is the 

 case, for instance, at Rutledge and Luverne 

 in Crenshaw County and at Brundidge in 

 Pike County, Ala. Between these out- 

 lying patches and the regular outcrop of 

 the St. Stephens is the usual succession of 

 the outcrops of the other Lig-nitic and Clai- 

 borne beds, with none of the Vicksburg 

 remnants, as yet detected, overlying them. 



We may sum up the evidence above pre- 

 sented, in the two following statements: 

 (1) No one has yet seen or recorded the 

 Grand Gulf actually in place beneath any 

 Tertiary formation. Eocene, Oligocene, 

 Miocene or Pliocene. (2) On the other 

 hand, it has been observed overlying, and 

 in direct contact with, every one of these 

 Tertiaries, to say nothing of the Ripley of 

 the Cretaceous. 



It has been inferred that it passes below 

 all the Tertiaries above the Vicksburg, sim- 

 ply because of the usual position of its 

 northern boundary, ignoring what Hilgard 



