DISCUSSION 



Discussion during van Straaten's paper 



Portion of text of van Straaten's paper leading into discussion: 



"We have originally a deposition of material in the form of laminae, but 

 they are disturbed by bottom animals. They are not disturbed on salt 

 marshes because there are no bottom animals up there. There are no 

 salt water animals which can live there because they are inundated too 

 infrequently and there are no land animals, land worms, because it is 

 still too salty. " 



Zeigler: 



van Straaten: 



Are those laminations then intertidal and does each tide give 

 you a lamination ? 



Yes, but with the exception that on the salt marshes whatever 

 laminations you find are only deposited during the exceptionally 

 high tides. The higher you get in the marshes, the rarer these 

 inundations become, so it is not each tidecibut each very high 

 tide in the marshes that deposits a lamination. 



Chronic: At about what level do you get this lamination known as the 



average tide ? 



van Straaten: The marsh lamination is formed just about at the mean high 

 tide level. 



Chapman: Do you get any removal of what has been deposited by the tide - 



I mean when you get a series of deposits and then suddenly two 

 or three inches are removed? 



van Straaten: Yes, that quite often happens, especially in creeks but not 

 usually working over whole surfaces, at least not in tidal 

 marshes . 



Oppenheimer: Then you might get a sort of scouring action in a sandy flooded 

 area ? 



van Straaten: Yes, I think that is also the reason, one of the reasons, that 



the upper parts of the tidal flats which are quite bare and open 

 for erosion and are not protected by plants, have a sandy com- 

 position because the clay is winnowed out continuously. 



Zeigler: With each of these double lanninae in one tide has anyone tried 



to work bac kwards and see how many tides it took to deposit 

 that three inches ? 



van Straaten: It depends upon what height you are above mean tide level, of 



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