Neotectonic crustal uplift on the continents and its possible mechanisms. The case of Southern Africa

According to a large volume of data an intensive crustal uplift began in th e Oligocene over most of the continental areas after a long period of relat ive tectonic stability. This Neotectonic uplift formed most of the present positive topographic features on the continents, and its strong acceleratio n took place during the last several million years. In many regions the upl ift was associated with magmatism. The main methods of studying the Neotect onic uplift are considered together with the data on the uplift of Southern Africa. In this area the uplift took place in the Early Miocene (up to 300 m) and in the Late Pliocene and Pleistocene (up to 900 m). It occurred wit hout stretching or shortening of the crust. Rapid erosion of the lower part of mantle lithosphere by a plume material is proposed as a mechanism of th e uplift. This material ascended from below and rapidly spread along the ba se of the lithosphere. Its spreading for similar to 1000 km during a few mi llion years is possible only under a low viscosity of normal asthenosphere (less than or equal to 10(19) Pa s) and a much lower Viscosity of a plume m aterial (less than or equal to 2 x 10(16) Pa s). As in Southern Africa, in most of the regions the Neotectonic uplift was associated with insignifican t shortening or stretching of the crust. This indicates that in some region s a plume material ascended from below and rapidly spread along the base of the lithosphere and eroded the mantle lithosphere in vast areas beneath th e continents. In regions with a hot asthenosphere a strong weakening of the mantle lithosphere which allows its erosion can be associated with a high temperature of the plume material. In regions where the asthenosphere is at moderate temperature weakening of the mantle lithosphere can result from i nfiltration of volatiles from the plume material.