Kurosegawa Terrane in Southwest Japan: Disrupted remnants of a Gondwana-derived Terrane

The Kurosegawa Terrane is an anomalous, disrupted, Paleozoic and Mesozoic l ithotectonic assemblage characterized by fragments of continent and contine ntal margins. It is located in Southwest Japan where it lies between two Me sozoic subduction complex terranes. The Kurosegawa Terrane is an exotic and far-travelled geologic entity with respect to its present position. Limest ones of the Kurosegawa Terrane formed along a continental margin yield fusu linacean fossils Cancellina, Colania and Lepidolina. Accordingly, the Kuros egawa Terrane was once situated within the Colania-Lepidolina territory in the East Tethys-Panthalassa region at a palaeo-equatorial latitude, possibl y close to the eastern margin of the South China and/or Indochina-East Mala ya continental blocks. These blocks had rifted from Gondwana by late Devoni an. They drifted northwards, passing through the Colania-Lepidolina territo ry in mid-Permian time, and amalgamated with the proto-Asian continent duri ng the late Triassic. Subsequently, during the Cretaceous, parts of the all ochthonous continental blocks and their associated tectonic collage were tr anspressed, dispersed, and displaced from the southeastern periphery of Asi a towards the north. As a result, the Kurosegawa Terrane is formed as a dis rupted allochthonous terrane, characterized by a serpentinite melange zone, lying between the adjoining Mesozoic subduction complex terranes.