76o JESSE E. HYDE 



lamellibranchs, etc., in very great abundance often only for a few 

 square feet ; the composition and structure of such a deposit suggest 

 that this accumulation where found was accomplished through 

 current-action. 



The deposits of this facies pass into the shales of the Scioto 

 Valley shale facies to the eastward by disappearance of the sand- 

 stones. This transition takes place rather abruptly and practically 

 all of the beds disappear simultaneously except those of the Buena 

 Vista member, which persists far into the shale area. The original 

 western margin of the Vanceburg facies in Ohio has been removed 

 by erosion. 



Five members can be recognized, of which all are persistent over 

 the area of the facies, except the topmost, which has been removed 

 by erosion at points in Pike and Ross counties. Although these 

 members appear to be distinct stratigraphic units over much of 

 the area, near the margins of the facies where the sandstones are 

 disappearing certain of the boundaries obviously become of uncer- 

 tain stratigraphic significance. 



The Henley shale member is named from Henley, Scioto County. 

 In the area of maximum development of the Vanceburg t3^e of 

 sandstones, it consists of alternating gray and red shales, but the 

 red color disappears to the eastward, together with the sandstones 

 of the facies. Along the western boundary line of Scioto and Pike 

 counties this member gradually increases in thickness from 5^ 

 feet at Buena Vista and 9 feet at Vanceburg to 34^ feet at Bain- 

 bridge in Ross County. Eastward and northeastward from this 

 line of sections in the Scioto Valley shale facies the thickness 

 increases rapidly, especially to the eastward. Along the Scioto 

 River the thickness increases from 55f feet at Rushtown in Scioto 

 County to 89 feet near Summit in Ross County. Several miles 

 east of Piketon in Pike County, its thickness has increased to 

 226 feet, if the superjacent Buena Vista sandstone is correctly 

 identified. The rapid westward thinning of this basal portion of 

 the Cuyahoga is believed to indicate that the Cincinnati dome was 

 an appreciable topographic feature on the shallow sea-floor of that 

 time. There is, however, no physical evidence of erosion of the 

 underlying thin Sunbury shale prior to its accumulation. 



