Deposystem architectures and lithofacies of a submarine fan-dominated deep sea succession in an orogen: A case study from the Upper Triassic Langjiexue Group of southern Tibet. (1st November 2015)

• Record Type: Journal Article
• Authors: Zhang, Chaokai; Li, Xianghui; Mattern, Frank; Mao, Guozheng; Zeng, Qinggao; Xu, Wenli
• Is Part Of: Journal of Asian earth sciences. Volume 111(2015)
• Page Start: 222
• Page End: 243
• Publication Date: 2015-11-01
• Subjects: Facies analysis -- Deposystem -- Submarine fan -- Langjiexue Group -- Upper Triassic -- Southern Tibet; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2015.07.013
• Languages: English
• ISSNs: 1367-9120

Abstract

Highlights: The Upper Triassic flysch was investigated in S Tibet (E Himalaya orogen). Four facies associations and nine facies comprise six architectural elements. One of the largest ancient fan systems was established, absent with inner fan. Fan deposystem displays six vertically-superposed and four laterally-coalesced fans. Medium-far transport from source area is suggested for mud-sand rich fan system. Abstract: Over thirty stratigraphic sections of the Himalaya orogen Upper Triassic Langjiexue Group in southern Tibet, China, were studied to interpret the environments and lithofacies. The facies associations channel (A), lobe (B), levee-interchannel (C), and basin plain (D) with nine facies (A1–3, B1–3, and C1–3) were distinguished. They form six architectural elements: channel-interchannel, overbank-levee, crevasse-splay, outer fan-lobe, fan-fringe, and basin plain. Taking into account the facies analysis, (sub-) deposystem correlation, paleocurrent dispersal pattern, and restoration of primary stratal width, the Langjiexue Group displays the architecture of a coalescing submarine fan-dominated deep sea deposystem, measuring about 400–500 km × 600–700 km in size or even more, one of the largest pre-Cenozoic submarine fans ever reported. Subdivisionally, four fans, lacking inner fans, could have coalesced laterally within the submarine fan deposystem, and at least six submarine fan developments were vertically succeeded by mid- to outer-fan deposits with progradational to retrogradational successions. According to the range of 30–70% of sandstone content, the fan deposystem is mud- and sand-rich, suggesting a medium-far (over 400–600 km) transport of sediment from the source area.