Multivariate analyses in paleobiogeography of Devonian rugose corals for revealing the multiple accretionary processes of the southwestern Central Asian Orogenic Belt

Biogeographic analysis has been applied on the globe- or orogen-scale tectonic evolution. The scarcity of paleobiogeographic study cases caused a debate as to the Late Paleozoic detailed accretion and convergence process of collages in the Central Asian Orogenic Belt. This contribution presents contrasting biota characteristics of the Early and Middle Devonian rugose corals in the Dananhu-Harlik Arc. By the multivariate analyses of the Early and Middle Devonian rugose coral faunas from series of the tectonic units in the Central Asian Orogenic Belt and neighboring areas, we reveal that two distinct paleobiogeographic units, namely, the Boreal and Tethyan Realms, were separated by the North Tianshan Ocean and Kalamaili Ocean in the Early and Middle Devonian, respectively. It means that the Dananhu-Harlik Arc experienced a paleobiogeographic change from the Boreal Realm in the Early Devonian to the Tethyan Realm in the Middle Devonian. Comprehensively considering the coral paleobiogeography, paleomagnetism, magmatism, provenance and distribution of ophiolites in the southwestern Central Asian Orogenic Belt, we speculate that the basal controlling factors of the Devonian coral paleobiogeographic pattern in the CAOB are the geographical isolation caused by the presence of oceanic basins, and the Mongolia and Kazakhstan Collages were separated by the North Tianshan Ocean sandwiched between the Dananhu-Harlik Arc and Central Tianshan Block during the Silurian to Early Devonian. In the Middle Devonian, the bidirectional and roll-back subduction of the North Tianshan Ocean caused the Dananhu-Harlik Arc separated from the Mongolia Collage by the Kalamaili Ocean and further moved towards the eastern Kazakhstan Collage. It caused the change of the rugose coral paleobiogeographic pattern in the southwestern Central Asian Orogenic Belt. The terminal convergence of Dananhu-Harlik Arc and Kazakhstan Collage occurred before the Latest Devonian and subsequently led to the formation of a new collage sandwiched by the Junggar-Kalamaili and South Tianshan Oceans.