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Sedimentation and changes of thermal and vertical stress gradients

Fyfe and Leonardos (1977), it will be noted, considered that sediments in a basin must be at least 10 km thick, in order that the conditions that will give rise to subduction can be met. These piles of sediments may be accumulated over a period of the order of 100 Ma. Consequently, thermal effects will have the time necessary to approach equilibrium conditions. Adjustment of the vertical and horizontal stresses in the sediments, as the result of the accumulation of sediments, will, of course, be progressive.

The geothermal gradient in oceanic lithosphere is not constant throughout. Near the spreading-ridge the gradient is several hundred °C per km of depth. This high gradient

Table 3.5

Differential depth of basin (km)

Maximum fibre stress (kb or 108 Pa)

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