GEOLOGY: W. H. BVCHER 
289 
A fourth factor of no less importance is brought out by consideration 
of the following facts: 
1. The formations of the Upper Ordovician consist essentially of the 
following sedimentary units, interstratified in irregular order: (a) Cal- 
careous shale, varying from highly fossiliferous to barren, (b) Dense, 
blue, argillaceous limestones, mostly barren (except in many cases the 
surfaces of the layers), (c) Fragmental limestones, varying from fine- 
grained to regular shell breccias. 
2. None of these units have a great horizontal extent, i.e. all formed 
simultaneously on different parts of the sea bottom. 
3. The shale may have any thickness, while the limestones are seldom 
over one foot thick. 
4. Single valves of brachiopods and isolated joints of Crinoids are 
common in the shales. 
5. The dense argillaceous limestones almost always show delicate 
cross-bedding. 
6. Current-rippled fragmental limestones are always overlain by 
shale. 
7. In fragmental limestones thin and dehcate shells and skeletons are 
commonly found broken, but the fossils in general show little wear. 
8. Large current-ripples are found in such formations as show a 
predominance of shale over limestones, e.g., the Eden and parts of the 
Richmond formations. They are absent, however, where limestones 
predominate, especially in the Fairview and McMillan formations. 
9. Fragmental limestones dominate in the Fairview and McMillan 
formations and show ample evidence of a stirring of the sediment, often 
of violent character, as e.g., the Rafinesquina breccias of the Belle vue 
horizon. 
From these data I conclude that the typical sediment of the Upper 
Ordovician seas in the region which now forms the Cincinnati Anticline 
was a clay with an abundant animal population, varying in density 
from place to place. The almost constant agitation of the sea bottom 
(obs. 4 and 5) furnished the fine shell powder which mixed with the 
clay, gives it its calcareous character.^^ Densely populated areas 
supplied it, especially after periods of storms, to adjoining areas of 
scarce population in sufficient quantity to form argillaceous limestones. 
This areal relation explains why argillaceous limestones are generally 
poor in fossils if not entirely barren. 
During exceptional periods of storm many feet of the muddy sedi- 
ments were thrown into suspension. In order to cloud water 20 to 
50 meters deep with sediment, as has been observed repeatedly in the 
