Comments on Sedimentary Rocks 



81 



and-mound, rain-drop impressions, gas pits, crystal imprints, mud cracks, 

 bedding, cross-lamination, scour and fill, imbrication, laminar corruga- 

 tion, intra- and interstitial flow, unconformities and diastems, nodules, 

 geodes, septaria, stylolites, cone-in-cone, and veinlets. Organic structures 

 are represented by tracks and trails, borings, and petrifactions. 



Sedimentary structures and their significance are treated in full by 

 Petti John ^ and by Shrock.^ 



X? 



Q.I;; 



02 



— o 



z- 



xs 



OL « 

 <5 



RADIX 10 



MEDIUM 



MEGAGRAINED 3.2 



MEDIUM 



MESOGRAINED .32 



MEDIUM 

 PAUROGRAINED -032 



MEDIUM 

 MICROGRAINED .0032 



CRYPTOGRAINED 



1/2 - 

 1/4 - 

 l/S - 

 k/16 - 

 1/32 - 

 1/64 - 

 1/128 - 

 1/256 - 

 1/512 - 

 1/1024- 



RADIX 2 



Figure 35. Tentative scale for carbonate rocks, grain diameters in millimeters, plotted 

 logarithmically. Scale based on radix 2 (used by Wentworth) added for com- 

 parison. (From DeFord. Reproduced permission Am. Assoc. Petroleum Geolo- 

 gists.) 



' Pettijohn, F. J., op. cit., pp. 120-168. 



' Shrock, R. R., Sequence in' Layered Rocks, New York, McGraw-Hill Book Co., Inc., 1948. 



