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Figure F14. Two main basin types recognized within arcs, as defined by Smith and Landis (1995). A. Volcano-bounded basin: small, irregular basins between individual volcanoes; larger linear troughs between volcanic chains; and thick basin fill preserved only in oceanic arcs, below sea level. Low areas between the series of rear-arc seamount chains shown on Figure F11 are volcano-bounded basins formed during growth of the chains at ~17–3 Ma. Site U1437 is located in one of these, which we refer to as the Enpo-Manji Basin (Fig. F15A). B. Fault-bounded basin: rapidly subsiding basins, deep (up to 10 km) with very high sediment accumulation rates (~1 km/My), and in continental and oceanic arcs. A fault-bounded basin is currently forming in the <1.5 Ma active rift (Fig. F6), and the broader zone of extension (<3 Ma) produced faults within the eastern half of the volcano-bounded basins between the rear-arc seamount chains (some visible on Fig. F15B); however, the bounding volcanic chains (not the <3 Ma extensional zone faults) exerted the primary control on accommodation in the basin drilled at Site U1437 (Fig. F15A).

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