(?Aaftt&i 6 



MISCELLANEOUS 



PETROLOGIC 



ANALYSES 



John R. Hayes 



The purpose of this chapter is to present a brief summary of methods 

 applicable to better evaluation of clastic and non-clastic rocks, in terms of their 

 classification and interpretation of conditions under which they were deposited. 

 More accurate classification of sedimentary rocks aids materially in all strati- 

 graphic analysis procedures and should be the goal toward which geologists 

 direct their interest. 



SIZE ANALYSES A basic property of clastic sediments is the 



size of the component particles. To evaluate 

 this variable, one must determine the range and relative abundance of various 

 size groups. In a clastic sediment the variation in particle size is continuous, 

 and to study and classify the rocks, arbitrary groups are established. An 

 analysis consists of measuring, in some manner, the range and relative abundance 

 of particles in the groups selected. Statistically, it is the determination of the 

 size-frequency distribution of the particles in a sediment. 



Purpose of Size Analyses 



The purposes of size analyses according to Pettijohn (1949) are as follows: 



95 



