The lithosphere is subject to fluctuations in temperature and pressure
during the formation of sedimentary basins. These fluctuations cause
metamorphic reactions that change the density of the lithosphere, which,
in turn, influences basin subsidence. This contribution develops a model
for sedimentary basin formation to assess the importance of this
coupling. The model shows that basin subsidence is significantly
affected by metamorphic densification. Compared to results obtained with
cruder density models, metamorphic densification accelerates subsidence
in the initial post-rifting stages as garnet becomes stable over an
increasing depth interval within the mantle, an effect that amplifies
the crust-mantle density contrast. For models with an extraordinarily
cold lithosphere, uplift is generated as a late stage of basin
evolution. In general, subsidence is not smooth but occurs instead in
small steps reflecting periods of accelerated/decelerated subsidence.
For typical crustal thicknesses, subsidence is controlled largely by
reactions in the mantle, and particularly those determining garnet
stability.