432 STUDIES FOR STUDENTS 



7. Surrounded by near-shore lacustrine deposits. 



8. Textural divisions grade into one another vertically, but not laterally. 



9. Fossils of still-water types of life. 



10. Bedding planes essentially horizontal. 



11. May be ripple-marked. 



Fig. 10 shows a section of laminated lake clays which were 

 found less than half a mile from the section in Fig. 9. Fig. 10 

 illustrates the still-water phase of lacustrine deposits as contrasted 

 with the near-shore phase deposited in the same lake. Another 

 contrast of this sort may be seen in Figs. 14 and 15, Jour. Geol., 

 XIX, 724. 



SHALLOW-WATER MARINE DEPOSITS 



ZONE OF MAJOR AGITATION 



1. In general coarse material. 



2. Rather high textural range (bowlders to mud). 



3. Sorted into lenses, pockets, irregular linear areas. 



4. Contain marine fossils with possible mixture of land forms. 



5. Distributed in rather narrow belt parallel with coast. 



6. Different textural divisions grade out laterally and vertically. 



7. Special markings; ripple-, rill-, wave-marks, mud-cracks. 



8. Sorted texturally and to some extent mineralogically. 



9. Considerable range in thickness within short distances. 



10. Cross-bedded. 



11. Constituents likely to be flattened. 



12. Bedding planes dip in all directions, but chiefly from shore. 



13. Bedding planes have dips varying up to angle of rest for the materials 

 (edges of deltas, ends of spits, etc.). 



By comparing these characters with those of the near-shore 

 phase of the lacustrine deposits, these two sorts of deposits are 

 found to have the same characters, with the exception of fossils 

 and a slight difference in distribution. There would also be a 

 difference in degree; that is, the marine deposits might contain 

 coarser material, have a higher textural range, thicker textural 

 divisions, etc. This type of sediment after cementation is illus- 

 trated in Fig. II which shows a section in the Potsdam sandstone 

 at the Dells of the Wisconsin River near Kilbourn, Wis. 



