Back-arc basins

Abstract

Back-arc or marginal basins are semi-isolated basins or series of basins lying behind the volcanic chains of island-arc systems (Karig 1971). It is generally accepted that these are extensional features produced by seafloor spreading type processes broadly similar to those occurring at mid-oceanic ridges (Ch. 5; see also Saunders & Tarney 1979, 1984; Crawford et al. 1981; Taylor & Karner 1983; Jarrard 1986). An extensional origin is supported by the high heat flow characteristic of such basins (Sclater et al 1972, Hawkins 1974) and by the occurrence of sets of magnetic lineations similar to those observed in normal oceanic crust. These were first described from the East Scotia Sea, an active back-arc basin behind the South Sandwich island arc in the South Atlantic (Barker 1972), and have subsequently been documented from the Lau, Mariana, south Fiji and west Philippine basins. Taylor & Karner (1983) have listed all known Neogene back-arc basins and compared their characteristics to those of normal oceanic spreading centres.