TYPES OF DEFORMATION ^^^ 



B. Tectonic or Orogenic Deformation. 



12. Tectonic joints. 



13. Earthquake fissures. 



14. Slaty cleavage. 



15. Fissility. 



16. Schistosity. 



17. Gneissoid structure. 



18. Folding — Anticlines, synclines, isoclines, fan folds, mono- 



clines, etc. 



19. Domes and basins. 



20. Faulting. 



C. Contact Deformations. 



21. Prismatic structure. 



22. Insolation joints. 



D. Complex Structures Partly Due to Deformation. 

 22,. Metamorphism. 



24. Disconformity and unconformity. 



ENDOGENETIC DEFORMATIONS. 



I. Endolithic Brecciation. This term is applied to brecciation 

 of strata caused by forces acting from within the mass, such as 

 crystallization and especially swelling or hydration, as in the case 

 of gypsum, etc. In this last case it is only the extreme of entero- 

 lithic structure. Similar structures are produced by contraction of 

 the rock mass on drying and the disruption into blocks or cakes 

 which are subsequently enclosed by later deposits and form an endo- 

 static rudyte. Examples of such have recently been described by 

 Hyde {11: 400-408) from the Coal Measures of Ohio. Beds of 

 fresh-water limestone intercalated in the series and deposited in a 

 playa lake were subject to periodic drying, as a result of which the 

 surface for several acres was broken up into polygonal blocks of 

 various sizes, the surfaces of which were frequently covered by 

 the shells of the animals killed in the drying of the lake. The 

 fragments seem to have been exposed for a while to weathering 

 and were then covered by a second flooding. Where the covering 

 deposits were muds, the limestone fragments form a striking series 

 of pebbles in a lutaceous matrix and often weather out in relief. 

 Many intraformational conglomerates may have such an origin. 

 Such breccias are of course closely similar to intraformational brec- 

 cias due to gliding movements as described under Section 4. 



