SKCT. 3] BASIN SEDIMENTATION AND DIAGENESIS 615 



hydrogen sulfide is liberated through bacterial breakdown of organic matter 

 and by sulfate reduction. In the extreme case, this results in the formation of 

 oxygen-free, sulfide-containing water, that is, a stagnant environment. 



Bacterial diagenetic processes, in particular the formation of highly reducing 

 conditions through the liberation of sulfides, have many interesting conse- 

 quences. The organic matter, which would normally be effectively destroyed in 

 an oxidizing environment, is only partially degraded and permitted to accumu- 

 late, in as yet an unknown manner, to huge reservoirs of petroleum. Trace 

 metals often associated with clays and living organisms are fixed in the sedi- 

 ments. Nutrients are regenerated within the sediment column and at the mud- 

 water interface and released to the overlying water, ultimately to re-enter the 

 productive cycle. The reduced environment appears to be particularly efficient 

 for the regeneration of phosphate and plays a special role in maintaining 

 nitrogen balance in the oceans through denitrification. 



Although more is known about basins than many other marine environ- 

 ments, large gaps are still present. The preceding discussion has attempted to 

 draw attention to our present state of knowledge and to indicate where further 

 studies can be profitably undertaken. 



References 



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