156 Kimball — Siderite-hasins of Hudson River Epoch. 



been set forth by Professor Dana in a remarkable series of 

 memoirs contained in this Journal from the years 1873 to 

 188S, inclusive. The recent work by C. D. Walcott, toward 

 locating the Cambrian and other points has removed all re- 

 maining doubts as to the general age of the rocks. 



The association with the same strata of siderite or clay iron- 

 stone, or, as more widely distributed, residues in situ of its 

 weathering decomposition, has also been pointed out with ref- 

 erence to the geographical and stratigraphical occurrence of 

 limonite beds throughout the same region. 



A recent study of the iron-ore bodies in course of very 

 active and systematic development by the Hudson River Ore 

 and Iron Company since the year 1875 at Burden, Columbia 

 County, N. Y., affords a number of interesting facts not unim- 

 portant in their bearing on the still rather obscure structural 

 geology of the western margin of the Taconic area extending 

 to the Hudson River, and indeed on the geology of the whole 

 Taconic belt. 



Sections from the river to the vicinity of Johnstown, on 

 the New York and Albany turnpike, traverse the Hudson 

 River shales to the base of the heavy body of fissile slates cov- 

 ering the western foot-hills of the Taconic range, with fine 

 exposures by excavations and diamond drill of the intervening 

 calcareous grits and ferriferous limestone beds, including in 

 places basins of siderite in unaltered form. The stratigraph- 

 ical relations of at least this horizon of iron ore are easily 

 established. The probability of its unity with a definite hor- 

 izon of other well known occurrences of ferriferous material in 

 altered or weathered form in numerous parts of the develop- 

 ment of the same series of strata is indicated by several 

 circumstances, such as appertain to an expansive bottom 

 whether littoral or marine. 



The iron-ore basins referred to are about a mile east of the 

 Hudson, between Catskill and Germantown railway stations, a 

 few degrees north of west from Copake, or directly opposite 

 that point in a line, that is, at right angles to longitudinal 

 axes of flexure in this part of the Appalachian system. The 

 intervening ground is occupied by a series of minor folds 

 whose longitudinal axes conform to the parallelism of the 

 same system. The ore-basins, four in number, constitute a 

 chain. Their longer axes are likewise parallel to the trend of 

 the Taconic and Catskill ranges. All but the first or most 

 southerly basin, and the terminal southern part of the second 

 or next basin to the north, have been folded and elevated into 

 anticlinals whose western and middle zones have been com- 

 pletely eroded to give place to the bed and terraces of the 

 Hudson. With the exception noted, the parts of the basins 



