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Major normal and growth faults are known to extend from sea floor through to base of the sediment wedge, their origins generally occurring along the then shelf break/uppermost slope and with overall less contemporary tectonics farther landward. The loci of extensional tectonics proceeds basinward, as the entire sediment wedge migrates offshore. Lesser sediment depocenters are successively incorporated due to sea level oscillations. The wedge-transiting faults appear to terminate often into plastic salt accumulations. Semiplastic unconsolidated clays, whose deposition are dominated by electromagnetic forces (ionic bonding), can create breakage/weakness zones along which extruded fluids from dewatering can migrate. Thus, the sea floor expression of significant faults can range from well-defined fault breaks to varying concentrations/domains of clay-sized particles.

Granting continental margin extension from rifting while a new ocean basin deepens, normal faults may occur within subsiding crust. Given synchroneity of extension and subsidence in sediments and crust, breakage zones in both might coincide. Upper crust is brittle fracturing. Lower crust temperatures and pressures suggest semi-plasticity with shear dislocations between separate masses. Lying between the upper and lower crust is transitional crust, possibly associated with fluid-injection along brittle fracture zones. As measured by earthquake seismology, crust maintains constant densities of 3.3 and 2.7 for oceanic and continental crust, respectively, and a transition zone between; such density transition indicates the Airy-Pratt controversy is unresolved. The mantle, being plastic and heterogeneous, contains convection cells having lateral extents ranging from 10-100 km to basin-spanning. Fluids from ocean and mantle could find avenues to transit from one to another.

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