Ripley Island Area of Southern Indiana. 337 



lent to the upper part of the Clinton east of the geanticline or 

 as practically equivalent to the entire eastern section. So far 

 no great difference has been noticed in the faunas in the upper 

 and lower parts of the Clinton, east of the geanticline. 



Additional notes on the development of the Cincinnati 

 geanticline. — The pre-Meso-Devonic origin of the Cincinnati 

 geanticline is shown best in Kentucky and Tennessee. Along 

 the crest of the geanticline Devonian rocks rest on Ordovician 

 formations, but both east and west of the crest the Devonian 

 rests on successively younger beds of the Niagaran. The 

 thinning out of the Louisville bed diagonally up the western 

 flank of the geanticline from at least 60 feet at Louisville to 

 nothing at Greensburg, and a similar thinning from the eastern 

 parts of Bartholomew and Shelby counties eastward toward 

 Greensburg, suggest similar conditions farther northward, in 

 Indiana. At Greensburg,* according to Mr. J. A. Price, the 

 sandy limestone of the Devonian rests directly upon the upper 

 layers of the Laurel bed, even the Walclron bed being absent. 

 The pre-Meso-Devonic age of the geanticline is indicated also in 

 southern Ohio,f where, according to Professor Orton, neo- 

 Devonian black slates or shales rest in succession on Niagaran, 

 Cayugan, and Meso-Devonic limestones on proceeding from 

 Highland county across Poss toward Franklin and Delaware 

 counties. The presence of unconformable contacts between 

 the Niagaran and Devonian in northern Indiana, at Delphi, 

 Georgetown, and Kentland,^: has been shown by Dr. E. M. 

 Kindle. The evidence at hand, however, does not demonstrate 

 the presence of the Indiana branch of the geanticline in pre- 

 Devonic times. 



The most interesting contribution of Dr. Kindle to the pre- 

 Meso-Devonic geology of northern Indiana is the demonstration 

 of the presence of strongly quaquaversal dips affecting Silurian 

 rocks previous to the deposition of the Devonian. At some 

 localities these dips suggested the presence of small domes. 

 Quaquaversal dips, although usually of a much less pronounced 

 character, are shown by Silurian strata also in central and 

 southern Kentucky, and along the western flank of the geanti- 

 cline in Tennessee. In tact, all the evidence so far accumu- 

 lated indicates that while the Cincinnati geanticline in general 

 shows a very simple structure, locally it may show strongly 

 quaquaversal dips connected with subsidiary folds whose axes 

 may be very divergent from the main axis of the geanticline. 

 Owing to the low inclination of the rocks over the greater part 

 of the area, these subsidiary folds attract much more attention 

 than they would in a more highly inclined series of rocks. 



* Indiana Geol. Surv., 24th Kept., pp. 87-90. 

 f Ohio Geol. Surv., Eept. for 1870, pp. 285-287. 

 % This Journal, vol. xv, p. 459, 1903. 



Am. Jour. Sci.— Fourth Series, Vol. XVIII, No. 107. — November, 1904 

 23 



