146 The Petrography and Genesis of Sediments 



SAMPLE NO. 7 (FIG. G, p. 169) 

 Serial number : 15. 

 Field number : 3-9-12-1911. 

 Formation : Matawan. 



Locality : Camp Fox, Chesapeake and Delaware Canal. 

 Appearance : Friable, sandy, gray-white marl, speckled with glauconite. 



Mechanical Analysis 



Sample s - 404 S m - 



Treated with dilute HC1 to dissolve lime. 



Per cent of 

 sample 



Lime-free residue 80.2 



Lime (by difference) 19.8 



Total 100.0 



Per cent of 

 lime-free residue 



Sands 87.8 



Silt 0.9 



Clay (by difference) 11.3 



Total 100.0 



Per cent of 

 total sands 



Coarse sand 0.2 



Medium sand 16.2 



Fine sand 60.6 



Very fine sand 20.0 



Extra fine sand 2.8 



Total 99.8 



Per cent of 

 very fine sand 



Light 57.3 



Heavy 42.2 



Total 99.5 



Magnetic Separation 



Per cent of 

 total heavies 



Attracted at 2000 ohms (glauconite) 86.0 =36.2% of very fine 



Attracted at full current 7.5"] 



Non-magnetic 0.4 L_ 6 % of very fine 



Magnetite 3.0 J 



Total 96.9 



Per cent of 

 2000-ohms 

 portion. 



Attracted at 2000 ohms, S. G.> 3.002 13.9 



Attracted at 2000 ohms, S. G.<3.002 (glauconite) 1 ... 86.1 = 74.0% of heavy=31.2% of 



very fine 



Total 100.0 



1 A minimum value for glauconite in this portion, since some glauconite came down 

 with the part heavier than 3.002. There are, on the other hand, some heavy minerals 

 especially mica in the part that flloated at 3.002 though their weight is doubtless less 

 than that of the glauconite that settled. Good approximations are probably : 



Glauconite 80% of heavy = 35% of very fine, 

 which leaves actual heavy minerals about 7% of the very fine. 



