SHAWI NEW AREA OF CARBONIFEROUS 559 



zoic floor upon which the deposits of the embayment rest and the 

 determination of the slope of peneplain in the territory immedi- 

 ately to the north, show that the upper end of the Gulf embay- 

 ment is not terminated by an ancient sea cliff, but that the 

 peneplain buried underneath the Cretaceous rises to the north, 

 becoming gradually less distinct, and in a few miles is apparently 

 intersected by a peneplain of later date. 



The surface of the Paleozoic rocks where exposed in Massac 

 County is the hard-rock floor upon which the Cretaceous and 

 Tertiary deposits of the embayment rest, and is thus a part of 

 the ancient peneplain that has been buried for several periods 

 and has only recently been exposed and slightly cut into. The 

 altitude of this old peneplain is here 370 to 400 feet, as deter- 

 mined by aneroid measurements, and the slope is about 30 feet 

 to the mile. These determinations accord with what is known 

 of the altitude and slope of this surface as determined from 

 numerous outcrops and well records in the surrounding region. 



Gravel and some less enduring material believed to belong 

 with the embayment deposits are found in numerous places on the 

 north side of the abandoned valley of the Ohio, and it is evident 

 that the embayment deposits once extended considerably north 

 of their present northern limit. There is some indication that 

 they may once have extended north of the low range crossing 

 the southern end of the state, 40 miles or more north of the 

 river. Some hills of peculiar, slightly coherent, poorly sorted 

 sandstone in the lowlands north of the range, as for example 

 near West Franklin, near Baldwin, and elsewhere, may possibly 

 be outliers of Gulf embayment deposits far north of any beds yet 

 recognized as belonging with them. The sandstone contains 

 in places angular fragments more than \ inch in diameter, and 

 in this and other respects does not resemble sandstone of the 

 same region known to be of Pennsylvanian age. It is, if any- 

 thing, more like slightly cemented glacial outwash, but differs 

 from that material in that it seems to contain no pebbles from 

 Canada, and in other respects it is not similar to the washed 

 glacial deposits of the region. The fact that the peneplains 

 in the range of hills seem to slope southward, though at a 



