168 Sioux City Academy of Science and Letters. 
that a seam of lignite at that horizon should be 
fairly constant over the whole strip of the country 
fringing the escarpment, but it should thin out toward 
the west. It is represented at Sargent’s Bluffs, on the 
Iowa side of the river, 11 miles north-northeast of this 
point. 
Further well drilling will shed more light on this 
question, and it is likely now that some interest has been 
aroused in the matter that such data will be preserved 
by the drillers more carefully in the future. 
Age.—-Bain® considers that the bed of lignite less 
than a foot thick, outcropping from the bluffs near the 
mouth of Ayowa Creek, and near the Ponca landing, is 
near the base of the Benton. Professor Todd has stated 
to the writer that the lignite throughout this locality is 
generally called Dakota. It would appear from the 
stratigraphic position, at least, of this bed that it is in 
the Benton near its transition to the Dakota. A few 
miles to the southeast in sec. 14, T. 29 N., R. 7 E., no such 
bed of lignite situated in the same relation to the Green- 
horn limestone is known to outcrop. Prospecting in secs. 
22 and 238 has disclosed the presence of lignite at that 
horizon and its absence at others. This bed is evidently 
fragmentary, and in the opinion of the writer it disap- 
pears altogether to the southeast with the thinning out 
of the Graneros shale. 
In the shaft in sec. 14, T. 29 N., R. 7 E., lignite was 
found at a depth of 60 feet, or more than 175 feet below 
the Greenhorn limestone. Obviously this is not at the 
same horizon as the Ponca lignite. The drillings and 
shaft in secs. 22 and 23 have disclosed the constancy of 
this bed, which, from its relative position, and the char- 
acter of the clays, sandstones, and shales accompanying 
it, is to be referred to the Dakota. Farther southeast, in 
the vicinity of Homer, and on the Winnebago Indian Res- 
ervation, the main lignite bed is above the level of the 
flood plain. Here only the character of the accompany- 
ing strata, not its position relative to the Greenhorn beds 
which are not far above it in the bluffs, proclaims it to be 
Dakotan. If the Graneros shale has thinned out in this 
vicinity as suggested by Bain for the south part of Wood- 
aBain, H. F., Geology of Woodbury County: Iowa Geol. Survey, Vol. 
5, L8S5, p, 297. 
