EARLE, INTERBEDDED IRON ORE DEr081T8 127 



found in places directly underlying limestones and shales. Concretions 

 in the lean ore were found to be as ferruginous as those found in the 

 richer ores; accordingly, the substitution took place before the fossil 

 fragments were consolidated into a bed by the cementing material. If 

 the ore is formed by a process of replacement, it should contain some 

 ferrous carbonate, yet this has never been found. The iron did not come 

 from above, for the Clinton ore beds are often horizontal, with no chance 

 for the action of downward-circulating waters. There is no doubt that 

 the ore was laid down in the form of an original precipitate at the same 

 general time that the inclosing sediments were deposited. It is likely 

 that there has been some enrichment of the deposits by the removal of 

 calcium carbonate. The iron is secondary only in respect to the organic 

 fragments, but primary with respect to the ore deposits as a whole. 

 Weathering has contributed to the present condition of the fonnation as 

 we find it to-day in some localities. Iron oxide and silica were deposited 

 together from solution in meteoric waters. Organic material caused the 

 retention of the iron in such waters. There is a connection between 

 silicic acid, iron and organic acids in the soils, and a deposition of iron 

 and silica together. Oolites were not originally calcareous. 



Smyth has probably been quoted more than any other writer in sup- 

 port of the sedimentary theory of origin. It is certain that the careful 

 microscopic work done by him is well worthy of careful consideration 

 before coming to any final conclusion in regard to the origin of these 

 deposits. Most of Smyth's work was founded on a study of the Clinton 

 ores of New York. 



Quoting D. H. Newland and C. A. Hartnagel (234, p. .50) : 



"The evidence in support of both views lias been traversed very tlioroughly 

 by C. H. Smyth, Jr., in a paper Vviiicli represents as well the results of long 

 experience and close study of the Clinton ores both in northern and southern 

 districts. There can Ije no doubt after an impartial perusal of Professor 

 Smyth's paper that the theory of sedimentary origin is fully substantiated for 

 most of the occurrences. For the ores under i)resent consideration, this is the 

 only explanation at all compatible with the conditions. 



"The stratigraphic features presented by the New York section of the Clin- 

 ton do not lend themselves to the conception of vertical circulations of ground 

 water such as would be required to dissolve and carry iron from the overlying 

 strata. The ore beds everywhei'e lie nearly horizontal : their dip is universally 

 toward the south, at an angle no greater probably in many places than that 

 given by the contour of the original sea bottom on which they were deposited. 

 At no time in their subsequent history have they been steeply inclined. More- 

 over, they are overlain by thick shales not readily permeable to water. Under- 

 ground flowage must necessarily be limited and be dependent for the most 

 part on the cropping out of the more porous strata-like limestone and sand- 

 stone layers. Thus it is directed rather along the bedding planes than across 



