44 NEW YORK STATE MUSEUM 



of igneous rock may lie within the mixed rocks, the strike and dip 

 in either case being accordant. Such phenomena are a natural 

 consequence of the more or less intimate cutting and injection of 

 the older rocks parallel to their foliation by portions of the syenite- 

 granite magma, the older rocks having been of the nature of large 

 and small inclusions in the rising magma. 



Structure of the Cambrian Strata 



The Cambrian strata of the three small areas mapped have been 

 only moderately tilted (in no case more than 20 degrees) from 

 their original horizontal position. In the area north of High Street 

 the dip is always 5 to 20 degrees toward the west, but the strike 

 varies from north 65 east near the middle of the area to almost 

 north-south at the north. These departures from horizontality have 

 been caused by unequal settling of the fault blocks upon which the 

 strata rest. 



Faults 



General considerations. It is well known that the southeastern 

 half of the Adirondack region is cut by many normal faults. In 

 all known cases the fault surfaces stand vertically or nearly so, 

 and the displacements vary from less than 100 feet to 2000 feet or 

 more. Most of these faults show a general northeast-southwest 

 trend, though some conspicuous ones show varying strikes. A num- 

 ber of normal faults were found within the Luzerne quadrangle, 

 and they are represented on the geologic map. The writer was dis- 

 appointed, however, in not finding positive evidence for many 

 faults which could be carefully studied. 



Within the area of Precambrian rocks of the eastern Adiron- 

 dacks it is often difficult to demonstrate the existence of faults and, 

 when a given fault has been proved to exist, it is usually difficult 

 or impossible to trace it across the country with any great degree 

 of accuracy because of scarcity of exposures due to accumulation 

 of Glacial and Postglacial deposits in the fault valleys. Because 

 of the character and structure of the rock masses (mostly igneous) 

 and the lack of any very clearly defined stratigraphic relations, it 

 is practically impossible to determine the actual amounts of dis- 

 placements, though in some cases minimum figures can be given. 

 Within the quadrangle such minimum figures are not definitely 

 known to be more than 1000 feet, but actual displacements may 

 have been much greater in some cases. 



