482 J. H. GARDNER STRATIGRAPHIC DISTURBANX'E IN OHIO VALLEY 



merely a section of the structure discussed in this paper. In the paper 

 by Dillcr above cited, Crandall is quoted partially as follows: 



"The most strikiug modifications of the general dip by transverse flexure is 

 found along a belt which extends from the Big Sandj' River, south of Louisa. 

 in liuwrence County, to a point opposite to and but a few miles east of the 

 dikes. The dip along this belt is to the northward from a ridge of conglom- 

 erate rock which elsewhere falls below the drainage along the border of the 

 coal field. It is along this slope that the oil and gas developments of Lawrence 

 and Martin counties are formd. The px'ominent geological basin centering at 

 Willard is formed by the junction of the northward dip with the general 

 southeast dip, increased by local depression. Willard is about six miles in a 

 direct line northeast of the dike. The dike is found near the juncture of two 

 lines of flexure : one parallel with the axis of uplift of the Coal Measures and 

 the other a transverse or secondary undulation of considerable local promi- 

 nence. Whether or not these conditions throw light on the occurrence of the 

 igneous rock far from any region of great disturbance, they form an interest- 

 ing, if not necessary, background to any general view of the dike and its sur- 

 roundings." 



Although not prominent on the surface and having only a very slight 

 topographic expression, this long line of folding and faulting is deep 

 seated in its character. There was evidently a yielding of the plastic 

 under-mass at the time of origin, so that the semi-fluid material far be- 

 neath the sedimentary series was folded in conformity with the overlying 

 structure. At points of sj)ecial Aveakuess, where faulting was prominent, 

 the pressure against the igneous mass was sufficient to force dikes entirely 

 across the sedimentary rocks to the surface. But at other points the 

 intrusive material penetrated only to such distances into the overlying 

 rocks as the pressure, viscosity, and resistance would permit. Where the 

 dikes found their way to the surface between walls of limestone, as in the 

 Kentucky-Illinois fluorspar district, ideal conditions existed for the for-' 

 mation of mineral veins. In the sandstone and shale rocks of the Coal 

 Measures in eastern Kentucky and in Penns3dvania no veins are found, 

 and in at least one of the two districts the intrusion did not reach the 

 surface. So it seems reasonable to suppose that on the central Kentucky 

 and Nashville domes of the Cincinnati geanticline dikes may have ]:)ene- 

 trated into the Cambrian and basal Ordovician systems, the pressure be- 

 hind the intrusions being relieved before the igneous rock reached the 

 surface, but crevices were formed on upward to the surface, which became 

 sealed by mineral veins of barite, calcite, and fluorite from ascending 

 vapors and solutions. 



On the accompanying map the names are shown of the difterent sec- 

 tions of the line of disturbance here discussed, which indicate something 



