sedimentary basins
Rift basins - Thermal Implication: McKenzie (1978), independently of Salveson, developed a quantitative thermal and mechanical model for lithospheric stretching and thinning based on the concept of uniform extension of the lithosphere. If a thermally equilibrated continental lithosphere of initial length x0 and thickness hc is extended instantaneously and uniformly by a factor β, then its new length will be given by x0.β and its reduced thickness is hc/β.
Upon finite uniform extension, the surface of the extended lithosphere drops allowing for the deposition of syn-rift sediments above pre-rift sedimentary sequences. As the thickness of the heat producing layer (the continental crust) is reduced, the thinned continental lithosphere is out of thermal equilibrium. The thermal anomaly corresponds to an excess of heat (following extension, the geotherm is too warm).
Uniform extension
Cooling relaxes the thermal anomaly. During cooling the density of the of the continental lithosphere increases while its thickness increases. This cooling produces a second subsidence called "thermal subsidence" or "thermal sag". This subsidence leads to the deposition of post-rift sediments.
The initial tectonic subsidence Si can be determined by balancing the pressure at a common depth below the deformed and the underformed lithosphere, given that both are in isostatic equilibrium.

Cooling