An updated age of Permian strata in the Raggyorcaka and Qamdo areas, Tibet and their paleogeographic implications

Abstract

The paleogeographic evolution of the North Qiangtang Block during the Middle and Late Permian has been a contentious issue in recent decades. In this study, the Permian foraminiferal faunas were studied from the Raggyorcaka and Wangka areas in northern and eastern Tibet. The foraminifera from the Xueyuanhe Formation in the Raggyorcaka area suggest a Changhsingian rather than a Guadalupian (Middle Permian) age, as previously determined. A review of Permian strata in the North Qiangtang Block confirms the widespread onset of the Lopingian (Late Permian) paralic sedimentary facies containing gigantopterid plant fossils and the fusuline Palaeofusulina fauna, which lies unconformably over the different pre-Lopingian strata. The similar Lopingian facies and pronounced unconformity across the North Qiangtang and Simao blocks are interpreted as the initial collision between the Simao/Indochina and the South China blocks.