98 W. P. JENNY 
into the plane of the map. A black station point means that the mag- 
netic force is directed toward the station; a hollow station point means 
that the magnetic force is directed away from the station, as indicated 
by the arrows in the legend. 
KENTUCKY 
The salient geological features of Kentucky are the Cumberland 
River arch, the Western geosyncline, the Cincinnati arch, the Lexing- 
ton dome, the Eastern geosyncline and the Pine Mountain thrust 
fault, as set forth on the inset of Figure 1. The most westerly corner 
of Kentucky is covered by Quaternary, Tertiary, and some Cretaceous. 
East of the Cumberland River arch only rocks of Pennsylvanian age 
and older are found, which are subdivided by the legend of the geo- 
logic map of Kentucky‘ as follows: 
| Conemaugh 
Pennsylvanian {Allegheny 
{Pottsville 
{Chester 
Mississippian {Meramec 
(Osage 
Devonian 
Silurian 
Ordovician fCincinnatian 
\Champlainian 
The Meramec crops out along a belt east and south of the Western 
geosyncline and is the outcropping formation along the axis of the 
Cumberland River arch west of the syncline. 
The core of the syncline consists of Conemaugh. 
The Lexington dome has its apex in the general neighborhood 
of Lexington, where the beds of the Champlainian crop out, sur- 
rounded by a vast area of Cincinnatian. 
The whole Eastern geosyncline and surroundings are covered by 
the Pottsville to within a distance of about 30 miles east of the axis 
of the Cincinnati arch. 
It is most characteristic that the Cumberland River arch and 
the Lexington dome show up as negative magnetic anomalies. From 
this we must conclude that the Chester or some beds of the Penn- 
sylvanian are of a greater magnetic permeability than the Meramec 
and further that the Cincinnatian, Silurian, Devonian, and Osage are 
of a greater magnetic permeability than the Champlainian and lower 
formations. ihe 
The areas of the two geosynclines are characterized by magnetic 
negative anomalies. 
W. R. Jillson, “(Geologic Map of Kentucky,” Kentucky Geol. Survey (1929). 
620 
