FACTS ABOUT MOUNTAIN REGIONS. 



787 



The folds in such regions are variously worn away in nature, and in this lies a large 

 part of the difficulty of ascertaining the relations of the included beds. On account 

 of the perplexities to be encountered, especially in regions of metamorphic rocks, or 

 where the upturnings have been greatest, an additional illustration of the subject is 

 here introduced. In Fig. 1135 there are five strata of like dip, 1, 3, and 5 consisting of 

 schist, and 2 and 4 of limestone. Suppose that the surface only is exposed to view, as 

 is true in many such cases: What are the several possible conditions as to the strati- 

 fication ? Some of these conditions are as follows: — 



(1.) Five independent strata lying in the order of deposition. 



(2.) Three faults (see p. 100), making 1, 3, 5, one stratum, and 2, 4, another. 



(3.) One fault, making 1 and 3 one stratum, and 5 another. 



Figs. 1135-1141. 

 1135. 



1136. 



1137. 



\ 



\ \ \\ \U\\\\\\ \\ '. \ 



1138. 



1139. 





1140 



1141. 



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•O -w v...' 



(4.) One anticlinal, as in (Fig. 1136), making 1 and 5 one stratum, 2 and 4 another, 

 and 3, a stratum folded on itself; whence No. 3 is the oldest of the series. 



(5.) The same as the last but reversed, as in (Fig. 1137), the fold being a synclinal, 

 and No. 3, the newest or overlying member of the series. 



(6.) A synclinal and anticlinal, as in Fig. 1138, making Nos. 1, 3, 5, the same stra- 

 tum, but 2 distinct from 4, and each 2 and 4 folded on itself. 



(7.) The same except that stratum 2 is made a synclinal and 4 an anticlinal, as in 

 Fig. 1139. 



