20 NEW YORK STATE MUSEUM 



the formation of the other CHnton strata. Salt and gypsiun exist 

 in extensive bodies within the SaHna formation of the Silurian which 

 outcrops across the State from Niagara to Albany county. Gypsum 

 occurs in seams up to 50 feet thick, but mostly from 4 to 8 feet, 

 in the section of the outcrop from Madison county west to Lake 

 Erie. Rock salt is not found at the outcrop owing to its solubility; 

 it is encountered on the dip of the beds at depths below 800 feet or 

 so and within the same east and west range practically as the gypsiun. 

 There are often two or three successive layers, separated by shale 

 or limestone with a total thickness of 150 feet or more. Natural 

 gas is present in local pools in the sedimentary series from the 

 Potsdam up to the top of the Devonian. The principal horizons 

 are the Trenton limestone, Medina sandstone, Salina waterlime, 

 Onondaga limestone, Marcellus shale and the Portage and Chemung 

 sandstones. The Medina sandstone is most prolific. The range 

 of the gas pools geographically extends from Lake Erie east to 

 Rome, Oneida county, and from Lake Ontario south to the Penn- 

 sylvania line. Petroleum occurs within a very limited area in 

 Cattaraugus, Allegany and Steuben counties, in sandstones of 

 probably Chemung age. The field is a northern extension of the 

 Appalachian field of Ohio, Pennsylvania and West Virginia. In 

 addition to the materials already listed there are occurrences of 

 barium and strontium compounds, small veins of galena, sphalerite 

 and pyrite, and disseminated deposits of pyrite in shales. Clays and 

 building stone are widespread. 



Palisades province. The Triassic rocks, which include the trap 

 or diabase that forms the Palisades of the Hudson, are exposed in 

 the southern part of Rockland county. They are more extensively 

 developed across the state line in New Jersey and reappear again 

 in northern Staten island. The Palisades represent the exposed 

 edge of a thick sheet of the volcanic rock that follows in the main 

 the bedding planes of sandstones and shales of Triassic age. The 

 rocks are not folded and there has been no mineralization of 

 importance in consequence of the intrusion, although a little copper 

 is occasionally found in the sandstones. The trap itself constitutes, 

 however, a valuable quarry material; it is exceedingly dense and 

 tough, most useful for crushed stone for concrete and road work. 



Coastal plain province. The southern part of Staten island and 

 the whole of Long island fall within the Atlantic coastal plain of 

 Cretaceous and Tertiary sediments. These consist of clays and 

 sands in horizontal beds, still unconsolidated, but concealed in most 

 places by later glacial materials and beach sands. Except for the 



