PLUME WINTER: THE P-T BOUNDARY CASE

The Permo-Triassic transition interval is unique in having 3 unusual global phenomena that never occurred in the rest of the Phanerozoic, viz., the greatest mass extinction, development of superanoxia, and initial breakup of the supercontinent Pangea. The end-Paleozoic mass extinction was double-phased, one at the Guadalupian-Lopingian boundary and the other at the P-T boundary sensu stricto. The coincidence in timing between the G-LB mass extinction, the onset of superanoxia, and the probable initial rifting of Pangea strongly suggests their causal link. The possible cause-effect link between the two Late Permian extinctions and the CFB (continental flood basalt) volcanism is favored by many; however, the only available material-based evidence for putative volcanism is the felsic tuffs in the Upper Permian in South China and Japan that appear inconsistent with the CFB link. The P-TB global environmental change was likely triggered by the episodic activity of a mantle plume, not through basaltic but felsic volcanism. The felsic volcanism can cause not only highly explosive eruption but also extensive delivery of air-borne ash. Alkaline felsic volcanism derived from a mantle plume may have played a significant role both in the G-LB and P-TB extinctions. When a plume head hits the bottom of preexisting continental lithosphere, alkaline felsic volcanism, often accompanying kimberlite/carbonatite, occurs in a highly explosive manner prior to a voluminous CFB eruption in a later stage that will drive post-extinction global warming. The “Plume Winter” scenario can explain not only the cause-effect link among the 3 unique geological phenomena of the P-TB but also the double-phased nature of the event. The G-LB event appears more important than the P-TB, because everything strange and geologically significant started at that time. The major re-organization of the mantle plume structure from the Pacific to the Atlantic regimes corresponds to the largest turning point in the Phanerozoic history of life from the Paleozoic to the Mesozoic-Modern regime.