34 NEW YORK STATE MUSEUM 



show the Lorraine to be 600 feet thick at Lorraine (Jefferson co.) ; 

 530 feet at Stillwater (Oswego co.) ; 549 feet at Central Square 

 (Oswego CO.) ; 640 feet at Chittenango (Madison co.) and 720 

 feet at Vernon (Oneida co.). According to these figures there is 

 somewhat of variation in thickness but not in any particular 

 direction. 



Oswego sandstone 



This formation is so named because of its prominence in. Oswego 

 county. It is the only representative of the Upper Siluric within 

 the quadrangle, and corresponds to the gray sandstone of Oswego 

 as used in Vanuxem's report. But one small area occurs within 

 the map limits and this forms the capping of the highest part of 

 Tug hill. This area represents the easternmost extension of the 

 formation which occupies many square miles in the southern part 

 of Lewis county. The Highmarket quadrangle, immediately to the 

 west, is literally strewn with slabs of this sandstone and the region 

 is characterized by numerous swamps and a sluggish drainage. 



Within the map limits the Oswego sandstone is a gray, fine 

 grained, thin bedded rock. The stratification is not very regular and 

 practically no shale is present. Fine examples of cross-bedding on 

 a small scale are common. A characteristic feature is the presence 

 of occasional yellowish spots of limonite, which are no doubt due 

 to the alteration of original iron pyrite. In marked contrast to the 

 underlying formation, the rock examined appeared to be barren of 

 fossils. The sandstone lies between the 2000 and 2100 foot con- 

 tours, thus showing a thickness of about 100 feet but with the top 

 not reached. 



STRUCTURAL GEOLOGY 

 Dip of the Paleozoic formations 



Movements since the deposition of the Paleozoic strata have 

 given them a very perceptible dip toward the southwest. This dip 

 may be determined, in a general way at least, by comparing the alti- 

 tudes of given horizons within the Port Leyden quadrangle and 

 south and west. For this purpose the top of the Trenton is chosen 

 because it is so clearly recognized in well sections. 



The top of the Trenton in the Rome well, as reported by Prosser,^ 

 is 205 feet below sea level, while 2 miles west of Port Leyden it Is 



^Am. Geol. 1900. 251137. 



