Upper Carboniferous sediments in the Simao region, Yunnan and their tectonic settings

The Simao region in Yunnan located in the eastern part of the eastern Tethyan tectonic domain was part of the margin of the Yangtze platform during the Late Palaeozoic and displayed the platform-basin sedimentary framework during the Late Carboniferous. Three types of sediments are recognized:littoral clastic sediments, platform carbonate sediments and deep-water volcanic turbidite sediments, the latter of which are characterized by volcanic turbidites and developed on a pre-existing carbonate platform or a continental shelf due to rift faulting. Vertically, these volcanic turbidites represent the alternation of the high-density volcanic turbidites and low-density volcanic turbidites, and may be arranged into five depesitional cycles. The increasing volcanism implies that the regional tectonism became progressively severe from the early stage to late stage of the Late Carboniferous. The volcanic rocks from the volcanic turbidites have the features of island-arc volcanic rocks, indicating that the study area was evolving from the passive margin to the arc-basin system of active margin during the Late Carboniferous.