Simultaneous supercontinent and superplume events may reinforce or cancel signals preserved in the geologic record. Alternatively, one signal may overwhelm the other. For instance, relatively low sea level during a 2.7-Ga superplume/supercontinent event may reflect direct hits of superplumes beneath the supercontinent. Although both supercontinent formation and superplume events occurred at 0.28, 1.9 and 2.7 Ga, global warming at these times indicates the dominance of superplume events in controlling climate. Enhanced deposition of black shales correlates with superplume events and with supercontinent breakup. Carbon isotopes in seawater, however, show positive excursions during supercontinent breakup at 2.2-2.1 and 0.8-0.6 Ga, but show mixed signals or no signal during other supercontinent or superplume events, probably due to negative feedbacks. Peaks in marine organism originations at 100, 280, and 480 Ma correlate with possible superplume events, whereas an overall decrease in origination rate in the early Paleozoic correlates with the growth of Pangea and destruction of shallow marine environments. Increased production rates of juvenile crust correlate with formation of supercontinents and with superplume events. There may be two types of superplume events: catastrophic events, which are short-lived (<100 My) and shielding events, which are long-lived (≥200 My). Catastrophic events may be triggered by slab avalanches in the mantle and may be responsible for episodic crustal growth. Shielding superplume events, caused by shielding of the mantle from subduction by supercontinents, are responsible for relatively small additions of mafic components to the continents and may lead to supercontinent breakup.
- Mantle plumes
- Superplume event