12. Color. Based on the Geological Society of America Rock-Color 

 Chart. For those samples where color was not determined in the field, 

 the sample was moistened in the laboratory for a color determination. 



13. Odor. A field description. A qualitative description of any 

 noticeable odors. 



14. Size Analysis and Statistical Measures. The following table is 

 presented for the conversion of phi units to millimeters: 



-j6 = log2 diameter (millimeters) 



Phi (^) Millimeters Geological Classification 



Granule 



-2 4.0 



-1 2.0 



1.0 



1 0.50 



2 0.25 



3 0.125 



4 0.0625 



5 0.0313 



6 0.0156 



7 0.0078 



8 0.0039 



9 0.00195 Silt 



Sand 



^9 



Clay 



Sample size fraction values are based on dry weight and given in phi 

 (16) units to the nearest whole percent. An American instrument company 

 sieving machine and TJ. S. standard sieves along with the pipette method, 

 based on Stoke' s Law (for computing settling rates of spherical particles), 

 were used for determining: 



(a) % Coarser Than Sand (L-lgQ . The fraction less than -1/6. 



(b) % Sand. The fraction greater than +4^. 



(c) % Silt . The fraction from 4/ to 9(6. 



(d) % Clay . The fraction greater than 9(6. 



(e) Sediment Type. Determined by the sand, silt, and clay ratios of 

 the sample based on the F. D. Shepard sediment triangle in the "Journal 

 of Sedimentary Petrology," Vol. 24, no. 3, pp. 151-158, 1954. 



(f) Phi Median Diameter (MdjzO. The middlemost member of the distri- 

 bution curve above which 50 percent of the diameters in the distribution 

 are large and below which 50 percent of the diameters in the distribution 

 are smaller and is expressed to the nearest hundredth of a phi unit. The 

 given value computed by the formula: 



136 



