NOTES ON MUD CRACK AND RIPPLE MARK IN 

 RECENT CALCAREOUS SEDIMENTS^ 



E. M. KINDLE 

 Geological Survey of Canada, Ottawa,, Canada 



During a trip to Florida and the Bahamas in the winter of 1920, 

 the writer kept in view as one of the objects of his seashore studies 

 the discovery of localities favorable for noting the characteristics 

 of mud cracks in Recent sediments. It seemed desirable that the 

 results obtained in laboratory experiments dealing with this sub- 

 ject should be checked by comparison with mud cracks formed on 

 the seashore. The following notes include also some observations 

 relating to ripple marks on calcareous sand. 



MUD CRACKS 



In the writer's experimental work, saline and non-saline mud 

 cracks were shown to develop, under the experimental conditions 

 imposed, sharply contrasted features. The polygons of the non- 

 saline mud cracks turned upward while those of the saline mud 

 cracks remained flat or curved slightly downward. It was stated 

 in this paper^ that while the experiments indicated the tendency of 

 the polygon margins to curl upward in the one case and remain 

 flat or curve downward in the other, the conditions found in nature 

 may often disguise or prevent any effective exhibition of these 

 contrasting tendencies. It was pointed out also that "the marked 

 differences observed in the experiments between the behavior of 

 fresh-water, highly saline, and moderately saline muds are not 

 ordinarily so well marked in nature as the accompanying illustra- 

 tions might lead the reader to expect."'' 



In the following notes the reader will see to what extent the 

 conclusions reached from experimental work regarding the contrasts 



^ Published with the permission of the director of the Geological Survey of Canada. 

 ^"Some Factors Affecting the Development of Mud Cracks," Jour. GeoL, Vol. 



XXV (1917), pp. 135-44- 



3 Op. cit., p. 143. 



138 



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