7 
FORT SCOTT FORMATION AND THE BOONE CHERT 621 
so productive of oil and gas, in northeastern Oklahoma and south- 
eastern Kansas. ‘These sands are present in the lower one-third 
of the Cherokee formation and are practically confined to the 
area inclosed within the 400-foot isobathic line.t The sands higher 
in the section extend farther to the west. The lenticular nature 
of the sands in the lower part of the formation indicates an oscillat- 
ing sea, and the occurrence of the greatest limestone thickness of 
the Fort Scott formation, to the west of the deepest part of the 
Cherokee basin, indicates a shifting of the basin in that direction 
as the Cherokee time interval progressed. 
Irregularities appear in the isobathic lines, as in northern 
Chautauqua County, Kansas, for example. These irregularities 
appear to be due to the presence of troughs during the early his- 
tory of the basin. These troughs may have been caused by erosion . 
of the Boone chert before the deposition of the Cherokee shales or 
may have been formed by downwarping during the deposition. 
The trough mentioned is shown as a flat on the Boone chert contour 
map of the Kansas Geological Survey.’ 
Many smaller irregularities appear on the southwestern side 
of the basin, indicating that the surface of the Boone chert was 
considerably eroded by the time the Pennsylvanian sea encroached 
upon the land to the west. This is well shown by the isobathic 
lines in Washington and Osage counties, Oklahoma. In several 
places the presence of old river valleys may be indicated by the 
successive curving in of the isobathic lines, such as the one extend- 
ing from the north edge of T. 23 N., R. 12 E. toT. 25 N., R. 10 E., 
Osage County, Oklahoma. 
The writer is indebted to Mr. A. W. McCoy, under whose 
direction the work has been carried on, and also to Dr. L. C. 
Snider, for valuable suggestions. 
t The productive sands in the fields farther west, which have generally been cor- 
telated with the Bartlesville sand, are considered from our studies to be at other 
horizons. 
2 State Geol, Surv. of Kansas, Bulletin No. 3, p. 197. 
