The original continental Craton of Stage A, which was rifted into two pieces in Stage C, is sutured back together and is stable once again in Stage I. This new continent is quite complex, however, compared with the Stage A Craton, and the basement rocks exposed at the surface are diversified. In the Enlarged And Detailed Drawing, the original West continent and East continent blocks have a volcanic arc trapped between them, and there are two foreland basin clastic wedges. These clastic wedges are likely composed of different sediments since one was formed from the erosion of a volcanic arc and one from a cordilleran mountain. There are also two suture zones of melange and a host of different igneous and metamorphic rocks. When everything is completely weathered and the continent is eroded to a peneplain, this continental Craton will be dominated by a veneer of quartz sand (QFL Diagram, yellow field) and limestones. Shales may also be present at first, but with enough time, these are eventually washed off the continental edge into the surrounding oceans.
The diagram below details processes of the rock cycle (also shown on Home Page
). Clicking the igneous rock names will take you to samples. See Tectonic Rock Cycle to go to the description of the model.
by Lynn Fichter
Thursday, October 02, 2014