Formation of the "steer's head" geometry of sedimentary basins by differential stretching of the crust and mantle

Abstract

If the lithospheric mantle is stretched over a wider region than the crust, postrift stratigraphic onlap will occur at basin margins, giving rise to a steer's head geometry. Space problems are avoided by making the total amount of extension in the lithospheric mantle equal to that in the crust. The predicted pattern of onlap agrees well with that observed if the lithospheric mantle is stretched over a fractionally wider region than is the crust. Thus, extensive stratigraphic onlap can be produced easily without recourse to sea-level rise or flexural rigidity.