Handbook of Paleontology 



57 



original structures, as bedding planes,, etc. The rock 

 is split through erosion into thin plates or may be so 

 split artificially. This is slaty cleavage. Our common 

 roofing slates are produced in this way. Slaty cleav- 

 age is most commonly found in clay mudrocks. Color 

 bands or fossils, if present, show the original bedding 

 planes. 



Figure 10 Unconformities. A Unconformity between igneous, 

 ig, and sedimentary rocks, s. B Parallel unconformity, or dis- 

 conformity, between two sedimentary series, si, s2. C Angular 

 unconformity or nonconformity- between two sedimentary series. 

 D Unconformity between igneous rock, ig, and two sedimentary 

 series : angular unconformitv between the two sedimentary series, 

 si, s2. 



Unconformities and disconformities. Unconformi- 

 ties and disconformities properly belong with original 

 structures, but they are better understood if they are 

 treated after a discussion of tilting and folding (figure 

 10). Where strata have been deposited in uninter- 

 rupted succession, have roughly parallel bedding 

 planes and have been similarly affected by movements 

 thev are said to be conformable. Such a series of beds 



