120 ANNALS NEW YORK ACADEMY OF SCIENCES 

 Lower or Niagarau Hiatu.s iuid (li.sconformity 



Guelph 

 Lockport 

 Kdclu'ster 

 Clinton 

 (Disconformity refers to an erosional unconformity.) 



The important points with reference to iron ore deposits to be deduced 

 from the above described conditions appear to be as follows: first, a thick 

 series of sedimentary beds of rapidly changing texture and composition, 

 clays and shales, sandstones and longer continued but less frequent lime- 

 stone deposits; second, an irregular shore outline with consequent effects 

 upon shape and size of sedimentary beds; third, a large area open to the 

 constantly changing waters of moving and probably rapidly moving 

 ocean currents from the south : fourth, to the east, land areas of the older 

 crystalline rocks of both acid and basic types, from which the iron salts 

 were dissolved in the course of weathering; fifth, a long period of slight 

 oscillations of the sea floor. After the deposits had been formed, they 

 were slowly elevated, and land areas were increased by a gradual emer- 

 gence of the sedimentary beds. No violent or pronounced folding took 

 place until the beginning of the Appalachian revolution, but mild dis- 

 conformities followed the slight uplifts accompanied by slight tilting. 



Erosion of the strata on this coastal plain gave access on tlic part of 

 the ferruginous waters to the porous beds, in which the water soon devel- 

 oped artesion conditions. 



Iron Ohe Deposits of the Clinton Formation 



The Clinton iron ore was first discovered in or near the town of Clin- 

 ton, New York. It was found later to be very common thi-ou^ilumt the 

 Upper Silurian, and the same type occurs also in other geological hoii- 

 zons. It has been traced extensively throughout much of eastern Ndith 

 America along the folds of the Appalachian system. 



The Clinton ores are usually found interbedded with shites. shales, 

 sandstones and impure limestones. 



types of ore 



The (Minton iron ores are known l)y various names according to text- 

 ure, composition and location. 



The fossil ores (Plates VIIT, IX, XVI) are composed of large masses 

 of marine fossils, such txi^ bryozoans. corals, crinoid stems, brachiopods 

 and many other characteristic fossils of that age. These fossils are usually 



