244 ‘ 
Notre on FAutt SrructuRE In INprANA. By Gero. H. ASHLEY. 
It has long been a prevalent idea with Indiana geologists that this 
State is practically without faults or fault structure. Prof. E. T. Cox, for 
many years State Geologist, says in his last report:* “Not a single true 
fault, or upward or downward break and displacement of the strata has. 
yet been discovered.” Prof. John Collett, so long a student of Indiana 
geology, says in describing Badger Bros.’ mine in Sullivan County :+ “An 
interesting feature of this mine was the discovery of a vertical dike or 
wall of inclusive clay, one foot wide, running a little east of north. This 
is the only fault, though here only a separation, that I have met with in 
the coals of Indiana,” etc. 
In view of such statements by the earlier workers, repeated by some 
of the more recent workers, it was not without surprise that the writer 
found that faults not only existed in the State, but were abundant and well 
exposed. It may be that this is truer of the coal measure area than of 
the rest of the State. Certain it is that the extensive mining of the coal 
gives a better opportunity for the study of these phenomena than is 
granted elsewhere, and further, the displacement of a coal bed is more 
readily noted when seen in a bluff or other exposure than a displacement 
in most other rocks. , 
The figures accompanying this note are selected from sketches and 
photographs made while engaged in a survey of the coal area of the 
State for the Department of Geology and Natural Resources. Time did 
not suffice for a detailed study of the faults, only such notes being ob- 
tained as were made incidental to the main work. 
In a general way it may be said that the phenomena observed con- 
sist of normal faults, either single, double, wedge or step faults, sometimes. 
accompanied with little or no notable crushing, or again accompanied by 
intense and extensive crushing, to be followed by the intrusion of clay or 
other substances; reversed or overthrust faults, crushed and thickened 
strata, due to tangential pressure, oblique jointing of strata due to the 
same cause, old surface crevices filled from above. Normal faults predom- 
inate, with down-throws varying from a few inches to forty feet or more. 
In number it may be judged from their abundance wherever extensive 
*1879. 8th, 9th and 10th Ann. Rep. Geol. Surv. of Ind., p. 3. 
41871. 2d Ann. Rep. Geol. Surv. of Ind., p. 205. 
