Handbook of Paleontology 



40 



percentage of soluble mineral constitutents ; also in 

 a cool climate where formed by glacial scouring. 

 Where lake or, especially, marine beds lack fossils 

 there is evidence of lack of suitable conditions of life — 

 too great salinity, turbid waters, too great cold etc. 

 When fossils are dwarfed there are likewise poor life 

 conditions. Thick deposits of gravels and sands such 

 as alluvial cone deposits indicate that mountainous 

 country is near-by. On the other hand, clays formed 

 by long and thorough decomposition indicate areas of 

 low relief as well as a moist, warm or temperate cli- 

 mate; while coal beds, as pointed out above, indicate 

 swamps and marshes. 



Figure 6 Outcrop of rock illustrating strike and dip (after 

 Jas. Geikie) 



Structures due to deformation. Sedimentary rocks 

 from the time they are deposited are subjected to de- 

 forming forces acting within the earth's crust which 

 disturb the original arrangement of the material of 

 the rock and modify the original structures. De- 

 formation structures, therefore, are secondary, and in- 

 clude folding and warping, faulting, development of 

 joints and slaty cleavage. 



