128 
Frank Carney 
INTRODUCTION 
The exactness with which the formations of a given region may 
be mapped is conditioned upon several factors: [a) Thick mantle 
rock sometimes so covers the terranes that in the absence of youth- 
ful drainage one cannot get good sections, (b) Some areas bear 
heavy glacial drift and consequently present equal difficulties in 
measuring the formations; this condition may persist even beyond 
the territory formerly covered by ice, particularly where the drain- 
age from the ice-sheet has made a great deposit of modified drift, 
(r) The attitude of the rocks also plays a part in the outlines pro- 
duced by weathering: for example, a region that has suffered 
marked disturbance of an orographic nature will yield locally to 
agents of degradation, producing good sections for study; whereas 
in a region where the rocks are generally horizontal, and the ero- 
sion cycle was interrupted in early maturity, the conditions are 
not apt to be favorable to a precise mapping of the rocks. Since 
the products of rock-decay are shifted chiefly by stream work, it is 
apparent that the quantitative value of these several conditioning 
factors is largely a matter of physiography. 
PHYSIOGRAPHY 
Mary Ann Township, from the standpoint of physiography, j 
involves some complexities. About one-half of the township was | 
glaciated (fig. i). The prevailing relation of drainage lines to 1 ; 
the ice-front encouraged the development of outwash deposits. I 
Some of these valleys are short but carried much water when the | i 
ice was contiguous; one valley was mature and for a short distance, i 
may have sloped toward the approaching ice, in which case ponded- I 
water occupied that portion of the valley. 
In order to account for the two rock exposures which show good i 
contacts of even part of the formations out-cropping in this town- i 
ship, and to understand why there are no more, it will be necessary | ■ 
eluded as a part of this report, involving about fifty square miles in the eastern 
part of Licking County, Ohio, was undertaken at the suggestion of Prof. Charles 
S. Prosser, whose encouragement through conferences and aid in the field I wish 
now to acknowledge, as a requirement for a Minor while a graduate student in the 
Department of Geology at Ohio State University. It is a pleasure also to express 
my obligation to Mr. C. R. Stauffer, who spent two days with me in this area. 
