STRATIGRAPHY OF THE DEEP-SEA FLOOR 



63 



water continues; adsorbed water moves from points of maximum 

 stress into the larger pores (Fig. 5). With increasing pressure there 

 is a virtual grain-to-grain contact. At this stage only a small part 

 of the adsorbed water remains and almost all the free water is 

 gone. Then, if the pressure is removed, there is some "elasticity" 

 or rebound due to the reattainment by each particle of its film of 

 adsorbed water. Modern studies (e. g., Lambe, 1953, p. 32) affirm 

 that Hedberg's (1936) concept is essentially correct. 



When the porosity is below about 35%, the primary consolida- 

 tion is virtually complete and further consolidation is the result 

 of plastic deformation and crushing of grains. Chemical readjust- 

 ments begin and there is pressure-point solution and redeposition 

 in adjacent regions under lower stress; colloidal matter tends to 

 crystallize with the formation of new minerals. At lower porosities, 

 cementation and further chemical readjustments (e. g., recrystal- 

 lization) result in low-porosity shales. Laughton (1957) has noted 

 a definite lamination of clays under pressure in the laboratory and 

 pointed out that this corresponds to the first stages of the forma- 

 tion of shales and laminated mudstones. 



Fig. 5. Processes in the consolidation and lithification of clay (Hedberg, 1936). 



