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Synchronous onset of the Mid-Carnian Pluvial Episode in the East and West Tethys: Conodont evidence from Hanwang, Sichuan, South China

2019; Elsevier BV; Volume: 520; Linguagem: Inglês

10.1016/j.palaeo.2019.02.004

1872-616X

Haishui Jiang, Jinling Yuan, Yan Chen, James G. Ogg, Jiaxin Yan,

Geological and Geochemical Analysis

The Mid-Carnian Pluvial Episode (or "Carnian Wet Intermezzo") interrupted the generally arid climate of the Triassic in different regions. An enhanced high-resolution time scale, especially with intercalibrated ammonoid, conodont and magnetic polarity zones, is required to understand the global coincidence of regional manifestations of this climatic change and possible causation factors. The termination of oolite-rich limestones and the initial influx of terrigenous debris at the Unit 1 to Unit 2 boundary in the Guanyinya and Qingyangou sections from Hanwang of the Sichuan Province, South China, are interpreted as a local shift from arid to humid climate. A detailed conodont sampling assigns this facies change to within the Mazzaella carnica range zone of the late Julian substage. Therefore, the conodont markers imply it is coeval with the onset of the mid-Carnian " Rheingraben Event" at the Rappoltstein reference section in southern Germany; and ammonoids in that section enable correlation to the beginning of a negative carbon-isotope excursion that coincides with the termination of the Yangtze Platform at the Longchang reference section in Guizhou, South China. The first occurrence of Parapetella? guanyinensis sp. nov. is very close to the onset of the interpreted Carnian Pluvial Episode at Hanwang and to the cessation of widespread shallow-water carbonate facies in South China. In contrast to this "Intermezzo" episode in the West Tethys region, arid conditions did not resume in South China in the Eastern Tethys until long after the termination of this wet climate in late Julian.