l80 NEW YORK STATE MUSEUM 



within the more active period of exploration and development of 

 the gas fields, Erie county has held a leading place in the industry. 



The source of its importance can be ascribed to the Medina sand- 

 stone which here seems to offer especially favorable conditions for 

 the storage of natural gas. The whole county is underlain by the 

 Medina formation which has its outcrop farther north in Niagara 

 county and is reached at depths increasing steadily toward the 

 south in accordance with the dip of the beds which is at the rate of 

 about 40 to 50 feet to the mile in that direction. The upper 100 

 to 140 feet of the formation comprises the main sandstone beds 

 within which the gas is commonly stored. Below is a body of red 

 and gray shales with their sandstone layers, goo feet or more thick, 

 also a part of the Medina but usually barren of gas. Well records 

 indicate usually a division of the sandstone into red and gray beds, 

 the former occurring above and measuring about 70 to 80 feet 

 thick, while the gray lies directly below or is separated from the 

 red by a few feet of shale. The gray sandstone averages perhaps 

 25 feet thick. A second bed of the gray is occasionally indicated 

 in the records and is referred to by some drillers as " white Medina." 



The Medina marks practically the lowest horizon at which natural 

 gas has been found in quantity in this region. A few wells have 

 been drilled into the lower formations, as far as the Trenton limestone, 

 without encountering additional pools. 



In the higher strata gas may be found locally in some quantity. 

 The Clinton shales have been found to contain pockets and the 

 Lockport dolomite often affords limited quantities of sulphurous 

 gas and water, which serve to establish the horizon where they 

 occur. The most favorable horizons above the Medina are the 

 waterlime in the Salina, the Onondaga limestone and the Marcellus 

 shale. The Onondaga limestone and the underlying waterlime bed, 

 according to Bishop, were probably the source of the gas in the 

 Zoar field in southern Erie county which for a time was quite pro- 

 ductive and probably had the record well that has so far been drilled 

 in the State with an estimated initial flow of 25 to 30 million cubic 

 feet a day. 



Bishop^ has compiled the following estimates of the thickness 

 of strata for the section from Lake Ontario to Cattaraugus creek. 



1 The Structural and Economic Geology of Erie County. N. Y. State Mus. Rep't 

 49, pt 2, 1895. 



