106 PROCEEDINGS OF THE AMHERST MEETING 



Dolores), or have beeu crushed, weathered, and recemented (all commercial 

 red or red mottled or streaked marbles and the Perce beds). 



Red limestones are not known to be forming today, either in marine or 

 fresh water, even where the conditions postulated for their original deposition 

 exist, as along the coast of Florida and the north coast of Yucatan. Red lime- 

 stones are now forming in Yucatan from the weathering and cementation of 

 wbite chalk and limestone. 



Red limestones were not originally red, but in all cases are due to atmos- 

 pheric weathering. They always occupy present or past unconformities or 

 crushed zones. They have no genetic relation to red beds of sandstone or 

 shale. The porous examples are now being weathered, the iron oxidized, and 

 the mass cemented by iron oxide and crystalline calcite. The dense examples 

 have already passed through the porous stage and have been cemented in 

 weathering. Limestones which do not become red on weathering are either 

 dense, lack iron compounds, or contain carbonaceous organic matter, or are 

 removed by erosion as fast as oxidation proceeds. 



Read from manuscript. 



Discussed by I. C. White, G. H. Chadwiek, T. W. Stanton, and R. S. 

 Bassler, with reply by the author. 



Discussion 



Dr. White: My observations agree perfectly with those of Dr. Galloway as 

 to the origin of the red color and iron in limestones, namely, that in all cases 

 it is the result of weathering or secondary causes. In the early eighties my 

 studies of the Clinton fossil iron area in Montour, Columbia, and Huntingdon 

 counties of Pennsylvania developed the fact that as we pass down below local 

 drainage, level 200 feet to 300 feet, the iron area disappears into a reddish 

 fossiliferous limestone, with only 8 to 10 per cent of iron remaining, and the 

 inclosing shales, both above and below, retain their natural unleached color, 

 instead of being white and leached, as they are where ore accumulation has 

 taken place, their iron content having passed through weathering agencies 

 from the shales to the cellular, honey-combed condition of the fossiliferous 

 limestone matrix. It is my opinion that the thick Clinton iron ores of Ala- 

 bama have had the same secondary origin source in all cases where iron ore 

 occurs, the inclosing ferriferous shales having been leached and decolorized 

 even at depths of 1.200 feet or more. However, in one deep boring no accumu- 

 lation of ore was found, and there the inclosing shales were not decolorized, 

 their iron remaining disseminated, and hence no leaching and no ore accumu- 

 lation. Most geologists regard the Clinton iron ore of Alabama as an original 

 deposition as ore, but your speaker thinks these ore deposits are the results 

 of weathering or of secondary causes. 



Professor Chadwick: In the Rochester region the Clinton (Furnaceville) 

 iron ore seems to represent a case of weathering of a fossiliferous limestone 

 with replacement by iron before deposition of the overlying Reynales lime- 

 stone: in short, a brief hiatus or disaster. 



Mr. Stanton : The Manitou limestone, which was cited as an example of 

 red limestone, is chiefly a gray limestone, as developed in Williams Canyon, 



