Cimmerian Geopuzzle: Insights from Permian Stratigraphy and Paleobiogeography of the Qinghaitibetan Plateau and Adjacent Regions

The Cimmerian continents constitute a complex assemblage of blocks and terranes extending from Turkey in the west to Southeast Asia in the east. These continental fragments rifted from Gondwana during the Late Paleozoic, triggering the opening of the Neotethys Ocean. However, their evolutionary history in Tibet and Southeast Asia remains ambiguous, owing to the intricate tectonic evolution of individual blocks in these regions. For instance, a suite of ophiolite belts occurs along central Tibet, defined as the Bangong-Nujiang Suture Zone (or Mesotethyan Suture Zone). Both the South Qiangtang Block to the north and the Lhasa Block to the south of this suture are considered components of the Cimmerian continent. Consequently, the early evolution of the Bangong-Nujiang Ocean and the eastward extension of this suture are critical for deciphering the tectonic history of Cimmerian blocks in the eastern Tethys. Our palaeobiogeographic investigations across Tibet and Myanmar reveal the following: 1. Distinct Permian stratigraphic and palaeobiogeographic patterns between the South Qiangtang and Lhasa blocks imply that the Bangong-Nujiang Ocean likely opened during the Artinskian; 2. Marked differences in Permian biogeographic turnover and stratigraphic successions between the Lhasa Block and the Tethys Himalaya suggest that the Neotethys Ocean may have initiated prior to the Guadalupian; 3. Palaeobiogeographic correlations between the Shan Plateau and Tibetan terranes demonstrate that the Mesotethys Ocean divided the original ‘Sibumasu’ block into an eastern ‘Sibuma Block’ and a western ‘Irrawaddy Block’. In summary, the Cimmerian continents of eastern Asia are composed of two distinct continental slices.