EARLE, INTERBEDDED IRON ORE DEPOSITS 151 



EXTENT OF DEPOSITS DOWN THE DIP 



Some artesian flows are found to extend for more than a hundred miles 

 from the outcrop, and flows tapped scores of miles from the intake are 

 not uncommon. If we admit that artesian conditions are responsible for 

 the existence of these ore deposits, then we must recognize that the limit 

 of artesian layers alone will determine the distance along the dip to 

 which these deposits can be expected to extend. As one fairly good ex- 

 ample, the case noted by Newland (234, p. 51) might be cited: 



"The recent exploration with tlie diamond drill has shown that there is no 

 notable change of character on the dip for distances of five or six miles from 

 the outcrop. Deep borings made some years since at Syracuse and Chittenango 

 found hematite below 600 feet, showing it to be of normal composition." 



WIDE DISTRIBUTION OF DEPOSITS 



Conditions that caused the formation of artesian runways, and later con- 

 ditions that brought about periods of heavy rainfall and rapid weathering 

 sufficient to produce the iron-bearing solutions that penetrated and filled 

 with iron ore these artesian runways or reservoirs, were so widespread 

 and extensive that no merely local results could follow, but rather the 

 development of a series of artesian slopes such as we find along the whole 

 Silurian shoreline, well filled with ferruginous material. 



OCCURRENCE OF OOLITIC AND FOSSIL ORES 



Whether the porous layers were limestone or sandstone would not affect 

 the question of genesis in any way, under this theory. Sandstone strata 

 might produce oolitic hematite, while fossiliferous limestone might pro- 

 duce the characteristic fossil ore, and still both types were dependent 

 upon similar artesian runways and penetrating iron-bearing solutions. 



VARIATIONS IN CHEMICAL COMPOSITION 



As these Clinton ores extend nearly two thousand miles along the out- 

 crops, and as the old land areas varied in composition, in some places 

 containing acid rocks and in others basic with different mineral con- 

 stituents, a difference in chemical composition of the ores might be ex- 

 pected. The fact, also, that the porous layers differed to some extent, 

 some possibly having a primary silica cement, others a calcareous cement, 

 and still others having no cement whatever, these and other minor varia- 

 tions in the original deposits would lead one to expect just such variations 

 in composition as we find in ore beds to-day. It would, therefore, still 



