STRATIGRAPHIC FRAMEWORK FOR THE PLUME MODE OF MANTLE CONVECTION

Mantle convection is a fundamental planetary process. Its plate mode is well established and expressed by Plate Tectonics; its plume mode is equally well established by geodynamisists, but overlooked by many geologists because of apparently lacking geological records. I developed a stratigraphic framework to translate the surface effects predicted by the plume model of Griffiths and Campbell (1990). The surface expression of ascending plumes lasts for tens of millions of years and leaves a distinct record, not only above the plume center, but also above the plume head margins and in distal regions (> 1200 km). Above the plume center, regional-scale erosion dominates prior to arrival of the plume head at the base of the lithosphere, followed by extensional collapse and flood-basalt eruption. A nearly complete sedimentary record may be preserved in distal regions, which did not experience any plume-related uplift. The plume margin is the most complex, because it undergoes uplift and erosion followed by subsidence and sedimentation and renewed outward-directed uplift and erosion as the plume head collapses and spreads laterally. Thus, plume margins are elevated and contain regional-scale unconformity-bounded stratigraphic sequences. The resultant spatio-temporal hiatus pattern is distinct on continent-scale geological maps. The identification of plume margins on these maps is hampered by the limited temporal resolution currently available on these maps.