Palaeogeographic constraints on the tectonic evolution of the Maizuru Terrane of Southwest Japan to the eastern continental margin of South China during the Permian and Triassic

The Maizuru Terrane in the Inner Zone of Southwest Japan consists of weakly metamorphosed ophiolitic complexes and Permian and Triassic strata. The Permian Maizuru Group is 1500–3000 m thick and consists mainly of mudstone, sandstone, and alternating beds of sandstone and mudstone. It is subdivided into lower, middle, and upper formations, and is overlain with angular unconformity by the Lower–Middle Triassic Yakuno Group. The Maizuru Group is characterised by the occurrence of the Capitanian Lepidolina kumaensis fauna in conglomerates of the middle and upper formations, and the Wuchiapingian Codonofusiella–Colaniella and Changhsingian Palaeofusulina–Colaniella faunas in lenticular limestones and conglomerates of the upper formation. Pre-Capitanian foraminifera are contained in limestone clasts of conglomerates of the upper formation and the basal part of the Yakuno Group. Examination on the stratigraphy, lithology, foraminiferal fauna, and Late Palaeozoic to Mesozoic tectonics in and around the Maizuru Terrane leads to the following conclusions. Capitanian and Lopingian limestone blocks and clasts were originally deposited on the continental shelf, and were subsequently redeposited on the deeper continental slope. Almost all of the pre-Capitanian limestone clasts were derived from the Akiyoshi Seamount accreted by the early Late Permian, except for those containing Verella prolixa and Pseudostaffella praegorski which were reworked from the shallow continental shelf. The Maizuru Terrane originated on the active continental margin located close to South China during Permian–Triassic time, but the depositional environment of the Permian and Triassic strata rapidly changed from deeper continental slope to shallow continental shelf.