Abstract

The Phanerozoic history of continental dispersal and coalescence contains an epoch of radical change at about the Middle/Late Triassic boundary (230 ±5 Ma), marked by (1) the final coalescence of Pangea by the contact of south China and Cimmeria with Laurasia and terminal compressive deformation in Australia and southern Africa, and (2) the incipient dispersal of Pangea by the onset of continental rifting in eastern North America and northwest Africa, Argentina, east Africa, and Western Australia. This epoch of coalescence and incipient dispersal correlates with a change from (1) an icehouse state to a greenhouse state, and (2) changes, from a fall to a rise, in the sea-level curve, in the emplacement of North American granite, and in the cumulative curve of reversed to normal magnetic polarity. These changes are interpreted as indicating the first major loss from the heat accumulated beneath Pangea, now represented by the Atlantic-African geoid high.

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