Deep seismic soundings in India and the origin of continental crust

The present day continental crust beneath stable cratons is generally thought to be 30–50 km thick1,2 although there are divergent views as to its initial thickness and the associated thermal and tectonic regimes3,4. Likewise, the lithosphere is believed to have been thinner in the Archaean, but its relationship to the crust at that time has not been specified. Structural details regarding the Archaean crust revealed by a Deep Seismic Sounding (DSS) study across the South Indian Craton5, supplemented by similar data from the Ukrainian Shield1, show a relationship between crust and mantle which apparently places important constraints on the thermo-tectonic conditions prevailing at the time of formation of the crust. We interpret these details as indicating that at one time the crust constituted the lithosphere, the Moho marking its base.