Bed type and flow mechanism of deep water sub-lacustrine fan fringe facies: an example from the Middle Permian Lucaogou
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ORIGINAL ARTICLE
Bed type and flow mechanism of deep water sub‑lacustrine fan fringe facies: an example from the Middle Permian Lucaogou Formation in Southern Junggar Basin of NW China Xin Shan1,2,3 · Xing‑He Yu2 · Lina Jin2 · Ya‑Long Li2 · Cheng‑Peng Tan2 · Shun‑Li Li2 · Jun‑Hui Wang4 Received: 10 August 2020 / Accepted: 13 October 2020 © The Author(s) 2020
Abstract Submarine or sub-lacustrine lobe deposits are important reservoirs, but the fan fringe deposits form heterogeneities within deep water fan deposits. Fan fringe facies records the complex sediment gravity flow types. By understanding of the bed types and flow mechanisms, we can identify the fan fringe deposit, which aids in the reconstruction of deep water fan and reservoir evaluations. The Jiucaiyuanzi and Dalongkou sections in the West Bogda Mountains preserve well-exposed 536-m and 171-m thick successions, respectively, of a deep water lacustrine depositional system from the Middle Permian Lucaogou Formation. Bed types of the Lucaogou Formation include high-density turbidite, low-density turbidite, incomplete Boumatype turbidite, hybrid event beds, and slump deposits. The Lucaogou Formation is interpreted here as a fan fringe facies due to the thin bed thickness that characterize turbidites and hybrid event beds, as well as the predominance of the isolated sheet architecture. Previous studies suggest that these deposits were considered as deposited in a deep water setting due to the absence of wave-related structures. The presence of abundant mud clasts in massive medium-coarse grained sandstone beds reflects the significant erosional capability and interactions between high-density turbidity currents and lake floor. The fan fringe facies here contains amalgamated and thick-bedded homolithic facies (~ 30%) and thin-bedded heterolithic facies (~ 70%). The examination of the bed type is of wider significance for facies prediction and reservoir heterogeneity in the sub-lacustrine fan fringe facies. Keywords Fan fringe · High-density turbidite · Low-density turbidite · Hybrid event bed · Lucaogou Formation · Junggar basin
1 Introduction Handling Editor: Cheng Lin Gong Edited by Jie Hao and Chun Yan Tang * Xing‑He Yu [email protected] 1
Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, Shandong, China
2
Department of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
3
Laboratory for Marine Geology, Pilot Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China
4
School of Earth Sciences, China University of Petroleum (Beijing), Beijing 102200, China
Mass-flow processes deposit submarine fans, which correspond to distinct constructional sediment bodies on the sea floor that develop seaward of a major sediment point source (Normark 1978; Walker 1978; Reading and Richards 1994). Important components of the submarine fan include the submarine channels, channel-lobe transition zones, and submarine
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