Geology of Seneca County. 61- 



with a doubled cross. Dotted lines are used to outline two of 

 the swampy districts, and the kame district. The direction of the 

 meridian is given by the western boundary of Junius. Quarries, 

 with slight exceptions, belong either to the Upper Helderberg or 

 the Portage ; they are marked with a cross. Special marks are 

 used for other outcrops of the Lower Helderberg, Marcellus, base 

 of Hamilton (H), Tully, Genesee, and Portage; those for the 

 Marcellus and Genesee shales being parallel lines, those for flag- 

 stones being oblong figures. Dotted lines mark supposed bound- 

 aries of formations. The outlines of the Upper Helderberg, 

 in western Waterloo, are hypothetical, being drawn straight 

 in the direction of the marsh exposures in Phelps. Many streams 

 are omitted; cataracts are not marked. 



The Portage, Lower Helderberg and Salina groups do not dis- 

 play their whole thickness in Seneca county. The fauna of the 

 former is intermediate between that of Ithaca and that of the 

 Genesee region, but is essentially a part of the former. 



Glacial geology is well represented by drumlins, sheet till, 

 striations, eskers, kames, delta-terraces, and large deposits of clay 

 and sand. 



The economic resources comprise building stone (limestone, 

 flags), cement-rock, rock for the lime-kiln, gypsum, gravel and 

 sand, road material, clay for making brick and tile, gas wells, 

 water-power, mineral springs, swamp deposits. 



The section of Seneca county (fig. 30) illustrates (1) the 

 changes in angle of dip ; (2) position of Seneca lake, beginning 

 at the outlet ; (3) the inferential position of strata at a distance 

 below the lake bottom, assuming that the Hamilton formation 

 remains of uniform thickness. 



Topography of the Plateau. 



The land surface of Seneca county comprises somewhat over 

 300 square miles ; the length from north to south is 32 miles, the 

 breadth from T to 14. On the north and south the boundaries 

 are artificial ; on the east and west they are formed by Cayuga 

 and Seneca lakes with their northward extensions. 



Seneca county does not compose a geographical unit, but 

 embraces parts of the New York plateau and of the low plain 

 which stretches to Lake Ontario. The passage from one to the 

 other of these two geographical features is at this point exceed- 



