Abstract
We present the results of field mapping, paleontology, and detrital zircon geochronology of newly found clastic rocks with intercalations of limestone in the Gaerqin area of Tibet (Gaerqin Formation). The Gaerqin Formation consists of sandstone, siltstone, and shale with intercalations of bioclastic limestone. Abundant Late Triassic (Norian) fossils are found in the limestone beds. The fossils include Distichophyllia norica, Retiophyllia litangensis, and Mesozoic Chaetetida. In addition, 273 detrital zircons were selected for U–Pb dating, yielding the following age groups: 210–300, 500–600, 800–1100, 1600–1800, and 2400–2600 Ma. More than 80% of the detrital zircons are older than ∼550 Ma, and the most reliable youngest detrital zircon age for the Gaerqin Formation is ∼219 Ma. The results indicate that the Gaerqin Formation formed in a shallow marine to bathyal continental slope environment, and represents the first reported Upper Triassic (Norian) strata in the Gaerqin area of Tibet. The findings also suggest that the Bangong Co–Nujiang Tethys Ocean was a bathyal basin by the Late Triassic.
Published Version
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