34 Cincinnati Society of Natwal History. 



REMARKS UPON SEDIMENTATION IN THE CINCINNATI 



GROUP. 



(Read June 4, 1889.) 



By Prof. Joseph F. James, M. S., United States Geological 

 Survey, Washington, D. C. 



I have in a former article* referred to the probable presence of 

 beaches in the rocks of the Cincinnati Group. The evidence of the 

 beaches consists in the presence of mud cracks, trails and burrows, 

 such as could only have been made upon an exposed surface, or at 

 least one covered with a slight depth of water. These evidences are 

 found at at least two horizons in the exposures at Cincinnati, one near 

 low-water in the Ohio River, and the other about three hundred 

 feet higher. There is evidence of a third beach at a still 

 greater elevation ; probably two hundred feet higher up. This 

 is exposed in several cuttings on Four-mile Creek near Oxford, 

 Ohio, about forty miles north of Cincinnati. In one of these 

 places there is a layer containing what appear to be rain-drop 

 impressions. The layer was found in 1887 by Mr. N. W. Perry, who 

 called my attention to it. The impressions are large and distinct, 

 some of them measuring a fourth of an inch in diameter. The rock 

 is a hard limestone, made up of finely comminuted material, and 

 occasionally containing the remains of brachiopods. In the same 

 layer are also found various markings referred to inorganic causes, 

 such as rill-marks, or marks made by running water. 



At another point, several miles away, but along the same stream, 

 are found well-defined ripple-marks, in some cases having considera- 

 ble extent. These, it is true, may have been, and probably were, 

 made under water, but the rain-drop impressions must have been 

 made on an exposed surface. The accompanying platef illustrates one 

 of the most characteristic specimens of rock with these impressions. 



Dr. Newberry, in an article upon " Circles of Deposition in Ameri- 

 can Sedimentary Rocks, "J and also in volume one " Geology'' of the 



*Science, Vol. V., p. 231, 1885. 



tThis will appear in a later number. — Editor. 



|Am, Asso. Ad. Sci. Proa, Vol. XXII., part 2, pp. 185-196, 1873. 



