9805210 Moser The problem of early crust formation in the Archean is a critical one bearing on planetary evolution and on crust-mantle relationships in what has become known as the 'tectosphere.' Because of the lack of exposure of the lower crust, there are very few places where this can be studied. However, the Kaapvaal area is one place where a major section of the crust has been tilted in the region surrounding the Vredefort impact structure. It is here that this study will focus on the relationship between the lower crust and upper mantle, focusing in particularly on the how the lower crust came to be welded to the upper mantle that now forms a strong mantle 'keel.' If successful, this study will shed light on the early evolution of the crust in South Africa, but with general applications to the origin of the lithosphere on earth and on other similar planets.
