22 



SCIENCE. 



[X. S. Vol. XVIII. Xo. 444. 



contacts he points out a very significant fact, 

 viz., " While the Vicksburg rocks show at all 

 long exposures a distinct southward dip of 

 some three to five degrees, the position of the 

 Grand Gulf rocks can rarely be shown to 

 be otherwise than nearly or quite horizontal, 

 on the average; although in many cases faults 

 or subsidences have caused them to dip some- 

 times quite steeply, in almost any direction."* 



And generally in the Gulf states, the land- 

 ward margin of the Grand Gulf almost in- 

 variably rests upon the Vicksburg limestone, 

 and many sections have been published show- 

 ing this contact. On the principle that, in 

 the absence of evidence to the contrary, a 

 formation follows next in chronological order, 

 that formation upon which it directly rests, 

 the Grand Gulf (or part of it) has usually 

 been placed in the geological column, next 

 above the Vicksburg limestone, i. e., in the 

 Miocene (or, as some now prefer to call it, 

 Oligocene). 



The application of this principle in Ala- 

 bama would cause us to place the Grand Gulf 

 at a number of horizons where we are per- 

 fectly certain that it does not belong, for 

 while in most cases it rests upon the Vicks- 

 burg limestone, yet we have recently seen it 

 in direct contact with the Upper Claihorne 

 and upon the Loiver Claiborne or Buhrstone, 

 on the one hand, and upon the Chattahoochee 

 Miocene, and directly upon., as well as far 

 above, the Pascagould (Miocene or Pliocene). 



So far as we know, no one has ever placed 

 the Grand Gulf between the lower and upper 

 Claiborne, or between the latter and the 

 Vicksburg. Too many sections have been 

 described showing the contact of these forma- 

 tions without any intercalated Grand Gulf, 

 to permit any such assumption. 



But the relations of the Grand Gulf to the 

 Vicksburg and post-Vicksburg Tertiary for- 

 mations have, perhaps, not heretofore been 

 fully set forth. Conclusive evidence as to 



* Many subsequent observations in Mississippi 

 and Alabama confirm this, and show besides that 

 the Grand Gulf beds, having been deposited upon 

 an eroded surface of the Tertiaries, exhibit great 

 variations in both the dip and the thickness. 



these relations is aii'orded, we think, at the 

 following localities : 



1. Chattahooche and Appalachicola River. — 

 If any part of the Grand Gulf occupies the 

 position assigned by Professor Dall to his 

 ' typical Grand Gulf,' i. e., between the Vicks- 

 burg and the Chattahoochee limetones (or- 

 appi'oximately at that horizon), there should 

 be somewhere on the gulf coastal plain a 

 section which would exhibit these beds in that 

 relation to each other. So far as we are 

 aware, no such section has ever yet come- 

 under notice. 



Certainly we should expect to find such an 

 exposure in that most complete and unbroken 

 section of the later marine Tertiaries afforded 

 by the Chattahoochee and Appalachicola. 

 Rivers. This series of the Neozoic rocks, 

 discovered by Langdon in 1887, has been 

 studied by a number of eminent geologists, 

 including Professors Pumpelly and Gilbert 

 Harris, and Messrs. Dall and Stanley-Brown, 

 some of whom have published descriptions. 



The most complete and carefully prepared 

 account of this section is that which appears 

 in Volume 5 of the Bulletin of the Geological 

 Society of America, ' Cenozoic Geology along 

 the Appalachicola River,' by Messrs. Dall and 

 Stanley-Brown. 



I'roin this article we make the following 

 quotations : " At a place on the left bank of 

 Flint River a few miles above the Florida 

 boundary line, known as Willey's Landing, 

 Professor Pumpelly states that the contact be- 

 tween the Vicksburg and undisturbed Chatta- 

 hoochee Miocene may be observed." 



" Beginning at the base of the column. Pro- 

 fessor Pumpelly has shown that the Chatta- 

 hoochee series rests on an erosion surface of 

 the Vicksburg or Orbitoidal limestone which 

 forms the culmination of the Eocene. We 

 have confirmed this by an examination of the 

 fossils submitted by Professor Pumpelly." 



In the ' 18th Annual Report ' of the Director 

 of the U. S. Geological Survey, page 330, Pro- 

 fessor Dall says : ' There is no marked break 

 in the stratigraphy between the Upper and 

 Lower beds so far as yet observed.' The 

 lower beds here referred to are the Vicksburg 



