322 Foerste — Ordoviciaii- Silurian Contact in the 



several miles apart gives unmistakeable evidence of dip. 

 Locally the dips ma} 7 be conspicuous though rarely exceeding 

 30 degrees ; however, the local nature of these dips is detected 

 easily, and usually is connected with folds and domes of rather 

 small extent. These local folds and domes are much more 

 numerous in the southern half of Kentucky and in Tennessee 

 than in the northern half of the area affected by the geanti- 

 cline, although tilted rocks are not uncommon along the western 

 branch of the axis in northern Indiana. 



The rocks involved in the folding include all of the Paleozoic 

 formations. Ordovician strata are exposed along the greater 

 part of the axis between northern Alabama and a point 26 

 miles north of Dayton, Ohio, a total distance of 400 miles. In 

 the southern half of Kentucky there is a sag along the axis in 

 consequence of which the crest of the geanticline is formed by 

 Mississippian (sub-Carboniferous) strata. North and south of 

 this sag of the axis, along the crest of the geanticline, are two 

 areas of considerable extent in which the Ordovician exposures 

 are practically continuous. Of these the southern area,* 75 miles 

 long and nearly 50 miles broad, includes all of central Tennessee. 

 The northern area,f 150 miles long and 85 miles broad, includes 

 the northern part of Kentucky and the adjacent parts of Ohio 

 and Indiana, between the towns of Lebanon, Richmond, and 

 Maysville, Kentucky, Dayton, Ohio, Richmond, and Madison, 

 Indiana. That part of the Cincinnati geanticline including the 

 southern Ordovician area is occasionally referred to as the 

 Nashville dome, while the part including the northern Ordovi- 

 cian area is sometimes called the Kentucky uplift or Cincinnati 

 dome. Farther northward in Ohio X and Indiana§ the crest 

 of the eastern and western branches of the Cincinnati geanti- 

 cline is formed by Silurian strata. 



Silurian Strata of Geanticline. 

 No trace of the Lower or Oswegan division of the Silurian, 

 including the Oneida and Medina, is exposed anywhere in the 

 area affected by the "Cincinnati geanticline. Middle Silurian 

 or Niagaran exposures, however, ranging from the Clinton to 

 the Guelph, are abundant. Cayugan or Upper Silurian 

 exposures, including rocks formerly known as Waterlime,|| are 

 known to occur in several areas but have not been studied. In 



* Geology of Tennessee, by James M. Safford, 1869, map. 



t The Richmond group along the western side of the Cincinnati anticline 

 in Indiana and Kentucky, Am. Geol., 1903, pi. 20 ; Silurian outcrops indicated 

 by dotted line. 



JOhio Geol. Snrv., vii, 1893, map. 



g Indiana Geol. Surv., 19th Kept., 1894, map ; much more accurate map 

 now in press. 



|| Silurian and Devonian limestones of western Tennessee, Journ. Geol., xi, 

 1903, pp. 701, 702. 



