EPISODICITY OF CONTINENTAL ARC ACTIVITY IN PHANEROZOIC AND ITS GLOBAL FLARE-UPS IN LATE CRETACEOUS: A QUANTITATIVE COMPILATION

Continental arc volcanoes have been suggested to release more CO₂ than island arc volcanoes due to metamorphism and magmatically induced decarbonation of wallrock carbonates stored in the continental upper plate through which the magmas traverse. Continental arcs may thus play an important role in long-term climate by helping to drive greenhouse events if they flare up simultaneously on a global scale. To test this hypothesis, we compiled geological maps of continents to reconstruct the spatial-temporal surface distribution of felsic-intermediate plutons, which we interpret to represent the eroded remnants of continental arcs as island arcs tend to be mafic. Complied data were imported into GIS and combined with global plate reconstructions. Our results show a non-steady, episodic nature of continental arc activity during the Phanerozoic. The surface area addition rates of felsic-intermediate plutons were low in the Neo-proterozoic and Early Paleozoic, and increased in the Late Paleozoic. Late Permian-Early Triassic and Late Cretaceous-Paleocene were two time intervals with the highest surface area addition rates of felsic-intermediate plutons manifested as the activities of Tethyan-wide and circum-Pacific chains of global continental arcs, respectively. We find that global continental arc activity declined after the Paleocene to low values comparable to continental arc lulls in the Early Paleozoic. Our results seem to confirm that global flare-ups of continental arcs may be correlated with the Cretaceous greenhouse and that the subsequent shut-down of continental arc activity was correlated with global cooling. Our compilation provides a basis for qualitatively upscaling continental arc processes (e.g. CO₂ release in volcanism and decarbonation and CO₂ consumption during surface erosion and chemical weathering), and integrating their roles played in global climate and ecosystem during Late Cretaceous and other periods in Neoproterozoic and Phanerozoic.