274 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
the right fork of the Fair mount syncline, and at the crossing of Mahon- 
ing Creek corresponds with what was formerly known as the Glade 
Run anticline. We have, then, instead of the Bagdad, Greendale, and 
Glade Run anticlines one continuous fold which will probably receive 
the name of the Greendale anticline. This eastward swing of the 
anticline between Pine and Mahoning creeks had been determined by 
the gas men previous to the present survey, but it had never been 
mapped, and consequently its position is not generally known. 
The data concerning the great synclinal basin east of the Greendale 
anticline have not yet been worked up, and consequently it is impos- 
sible to say what are the details of structure in this broad basin. 
In the southern part of Armstrong and Indiana counties, errors 
have been found in the former determination of the position of the 
axes. Heretofore the Roaring Run anticline was not supposed to 
extend to the north much beyond the crossing of Crooked Creek. In 
the course of the present work this fold was found to cross Crooked 
Creek and then swing sharply to the east and to enter Indiana County 
along the South Fork of Plum Creek. 
One of the most pronounced errors in the previous determinations 
of the structure of this region occurs in Indiana County, where numer- 
ous diamond-drill holes show that there is a pronounced syncline 
through the town of Indiana, where formerly an anticline was supposed 
to exist." The first anticline west of Chestnut Ridge is one of the 
most pronounced folds of the region. It has been traced continuously 
from the AVest Virginia line to Coneinaugh River, and in previous 
reports it was extended across Indiana County, and was given the 
name of the Indiana anticline. This name has been extensively used 
by several writers, and is in current use to-day to designate the long 
anticlinal fold previously described. The present work has demon- 
strated clearly that this anticlinal fold dies out near the Conemaugh 
River, and the two synclinal basins on either side coalesce and extend 
beyond the town of Indiana along a continuation of the same line 
that the anticline follows farther south. 
The direct results obtained during the course of this survey in the 
Allegheny Valley are regarded as the most important contribution to 
the economic geology of the coal field that has appeared during the 
present decade. When rightly understood they are of the greatest 
importance to oil and gas men and of nearly equal value to coal 
operators. 
The amount of data required for such work is enormous, and con- 
sequently the work of office preparation is necessarily slow. The 
maps of the Indiana folio are now being engraved, and before many 
months they will be ready for distribution. The reports on the other 
quadrangles are not so far advanced, but will be published as soon as 
it is possible to assemble the data and engrave the maps and print 
them. 
"Richardson, G. B., The misnamed Indiana anticline: Jour. Geol., Vol. X, pp. 700-702. 
