436 A. F. FOERSTE LIMESTONES OF TENNESSEE AND KENTUCKY 



tion from the preceding rocks consists in the fact that at many localities 

 the}'^ become still more calcareous, owing to the presence of numerous 

 fossils, chiefly large forms o( Pldtystrophia lynx ^nd occasional specimens 

 of Hehertella occidenUdis. At other localities, however, these fossils do not 

 occur in the upper parts of these calcareous clays, or at least occur but 

 rarel}', and are difficult to find. Since these beds form the main parts 

 of the Ordovician exposures as far east as Thomas branch, often forming 

 steep cliffs, notwithstanding their clayey character, it is practically cer- 

 tain that at least the unfossiliferous parts of those calcareous clays were 

 included in the original Cumberland sandstone section. 



The richly fossihferous blue Ordovician limestones, which are often 

 present in considerable thickness in the Cumberland River valley, seem 

 to belong about 100 feet below the Fowler limestone. 



Equivalency of Cumberland sandstone and Madison, bed. — The fossils col- 

 lected in the Fowler horizon belong to the Richmond group. Several of 

 them are especially common near the top of the group. The same fos- 

 sils and closely related species have been found in the immediate vicin- 

 ity of Moreland and also at several localities west of this station, in 

 Central Kentucky. At these locaHties they occur above a series of clayey 

 limestones which are })ractically unfossiliferous. These cla3'e3^ lime- 

 stones weatlier more readil}^ than the richly fossiliferous blue limestones 

 beneath or the fossiliferous limestones above. They have been traced 

 northwestward as far as the Ohio river. In the later reports of the In- 

 diana surve}^ they are called the INIadison beds. There is no doubt that 

 in southern Indiana and northern Kentucky the Madison beds are merely 

 the upper unfossiliferous part of the Richmond group. There, as well 

 as near Moreland, a few limestones with Richmond Group fossils imme- 

 diately overlie the thicker, nearly unfossiliferous Madison Bed section. 



Possibly a part at legist of the unfossiliferous beds underlying the 

 Fowler limestone along the Cumberland river belong to the horizon of 

 the Madison bed. At any rate, the Fowler limestone itself is of Richmond 

 Grou}) age and the Richmond group is present at the crest of the anti- 

 cline where it is cut by the Cumberland river. 



If the interpretation of the rocks above given is correct, it will be seen 

 that the term Cumberland sandstone includes a much larger series of 

 rocks than the name Madison bed. The clayey rocks, with larger speci- 

 mens of Platystrophia lynx, may even belong to the Lorraine. 



EVIDENCE OF RICHMOND GROUP ON AGE OF CINCINNATI ANTICLINE 



So far as present observations indicate, the Richmond group thins 

 rapidly southward, but it remains to be proved that it is thinner along 



