STUDIES FOR STUDENTS 



431 



Material likely to be coarse. 



High textural range (bowlders to silt). 



Well sorted into lenses and pockets and arranged in linear areas. 



Textural divisions grade out in all directions. 



Fossils from running-water, surf-water, and still-water habitats. 



6. Constituents well or poorly flattened. 



7. Cross-bedded. 



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

 Rather abrupt variations in thickness. 



Bedding planes dip in all directions, predominantly from shore. 

 Bedding planes dip at angles varying up to angle of rest for the mate- 

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



12. Distributed in narrow belt parallel with lake shore. 



I. 

 2. 

 3- 

 4- 

 5- 



9- 

 10. 

 II. 



-^-^ 



Fig. 9. — A near-shore phase of lacustrine deposit in Wisconsin. 



Fig 9 shows some lacustrine sand and gravel exposed in the 

 margin of the bottom of an extinct lake in Wisconsin. 



LACUSTRINE DEPOSITS (STILL-WATER PHASe) 



Material fine in texture. 



Low textural range (sand to silt). 



Well sorted into definite layers. 



Rather uniform in thickness. 



Beds likely to be finely laminated (in some cases 20 to the inch). 



Distributed continuously over large or small areas, according to size 



of depositing lake. 



