A joint receiver function and gravity study of crustal structure beneath the incipient Okavango Rift, Botswana

Abstract

Rifting incorporates the fundamental processes concerning the breakup of continental lithosphere and plays a significant role in the formation and evolution of sedimentary basins. In order to decipher the characteristics of rifting at its earliest stage, we conduct the first teleseismic crustal study of one of the world's youngest continental rifts, the Okavango Rift Zone (ORZ), where the magma has not yet breached the surface. Results from receiver function stacking and gravity modeling indicate that the crust/mantle boundary beneath the ORZ is uplifted by 4-5 km, and the initiation of the ORZ is closely related to lithospheric stretching. Possible decompression melting of the subcrustal lithosphere occurs beneath the ORZ, as evidenced by a relatively low upper mantle density based on the gravity modeling. Key Points First seismic study of incipient Okavango rift crust Symmetric crustal thinning of 4-5 km indicating pure shear Rifting initiation by relative motion of cratonic blocks