132 The Petrography and Genesis of Sediments 



facies of the Magothy occurs here at the head of Chesapeake Bay, there- 

 fore just below the mouth of the present Susquehanna. It points to the 

 possible existence of that stream in Cretaceous times. 



SAMPLE NO. 3 (FIG. C, p. 169) 

 Serial number : 13. 

 Field number : 3-7-13-1911. 

 Formation : Matawan. 



Locality : Chesapeake and Delaware Canal. 

 Appearance : Typical Matawan ; black glauconitic clay with little mica. 



Mechanical Analysis 

 Sample 8.967 gm. 



Per cent of 

 sample 



Sands ' 64.8 



Silt 6.3 



Clay 27.0 



Total 98.1 



Per cent of 

 total sands 



Coarse sand 4.8 



Medium sand 5.3 



Fine sand 5.7 



Very fine sand 59.4 



Extra fine sand 24.8 



Total 100.0 " 



Per cent of 

 very fine sand 



Light 71.2 



Heavy 26.3 



Total 97.5 



Magnetic Separation 



Per cent of 

 heavies 

 Attracted at 2000 ohms (glauconite) 2 . . . . 63.7 =16.8% of very fine 



Attracted at full current 28.6"] 



Non-magnetic 0.5 I = 83% of very fine 



Magnetite 2.9 J 



Total 95.7 



Per cent of 

 21100-ohms 

 portion 



Attracted at 2000 ohms, S. G. > 3.002 12.0 



Attracted at 2000 ohms. S. G.< 3.002 (glauconite) 2 87.1 = 14.6% of very fine 



Total 99.1 



'Total sands by summation of parts. 



3 The separation with the solution of density 3.002 was made to facilitate study of 

 the rare heavy minerals. A small part of the glauconite came down with the heavy 

 minerals while much mica remained floating with the glauconite. The value for per- 

 centage of glauconite after the separation at density 3.002 is, however, probably nearer 

 right than before this separation, so that glauconite may be taken as about 15% of the 

 very fine sand, leaving about 11% of true heavy minerals. 



