1^^ NEW YORK STATE MUSEUM 



northern part of Cattaraugus county and central and northern 

 Chautauqua county productive pools have been encountered in the 

 last few years by deep wells bottomed some 1500 feet or more below 

 the Chemung and Portage horizons. The lower gas-bearing strata 

 are assigned with some degree of probability to the Medina formation. 

 The thickness of the Portage strata in western New York is placed 

 by Clarke and Luther at about 900 feet. On the line of the Seneca 

 river it is 888 feet; and at Seneca lake 1122 feet. The Chemung 

 formation, according to the same authorities, is over 1000 feet. 

 Along the Genesee the measured thickness is given as 10 15 feet; 

 at Seneca lake, 1050 feet. In the Cayuga Lake region and farther 

 east to the Chenango valley the strata are even somewhat thicker 

 than indicated for the western sections. 



The Marcellus beds are a black, soft bituminous shale that lies 

 above the Onondaga limestone in the area west of Schoharie county, 

 marking the beginning of the extensive shale accimiulation that 

 continued through the Hamilton period. The black shale is 40 to 

 60 feet thick in the natural gas region and is a well-marked horizon 

 that commonly yields pockets of gas and occasionally more persistent 

 flows. It is likely the original source of much of the gas occurring 

 in the Onondaga limestone. The shale constitutes an element of 

 some difficulty and even danger to the exploration for salt in the 

 western part of the State, particularly in the excavation of shafts, 

 owing to the gas flows that are frequently encountered at this 

 horizon and that are sometimes violent when first tapped. 



The Onondaga limestone and the Bertie waterlime, the latter 

 a part of the Salina series, constitute a subsidiary gas zone in parts 

 of Cattaraugus and Erie counties. The two form practically a 

 single horizon, so far as this area is concerned, for they are contiguous 

 formations or at most separated by a thin sandstone layer (Oriskany) . 

 From the drill records it is frequently impossible to distinguish 

 between the two limestones. Most of the gas in the Onondaga 

 seems to occur in the " bull-head " stratum near the base which 

 is more porous and permeable than the Comiferous beds above. 

 The largest flows from these formations have been reported in the 

 district in southern Erie and within Cattaraugus county where the 

 wells are 1500 to 1700 feet deep. 



The Medina sandstone represents the most widespread natural 

 gas zone in the State. Its importance did not gain recognition 

 until quite recently but is now fully appreciated by drillers who 

 are actively engaged in the search for new gas supplies in this horizon. 

 The first large district in this sandstone was opened in Erie county 



