--> Abstract: Promises and Problems of Two-Dimensional Nonmarine Sequence Stratigraphic Analysis Using Hierarchical Depositional Cycles – An; #90063 (2007)

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Promises and Problems of Two-Dimensional Nonmarine Sequence Stratigraphic Analysis Using Hierarchical Depositional Cycles – An Example from Outcrop Lower Permian to Lower Triassic Fluvial-Lacustrine Deposits, Southern Bogda Mountains, Turpan Intermontane Basin, NW China

 

Yang, Wan1, Qiao Feng2, Yiqun Liu3, Neil Tabor4, Stephanie Thomas4, Yi Yang3, Guozi Sun3, Bei Sun3 (1) Wichita State University, Wichita, KS (2) Shandong University of Science and Technology, Qingdao, China (3) Northwestern University, Xian, China (4) Southern Methodist University, Dallas, TX

 

Correlation of hierarchical cycles among individual sections may be effective in sequence stratigraphic analysis of nonmarine deposits with rapid facies changes and common erosional surfaces. Two long (1049 and 1616 m) and four short (~100-m each) Lower Permian-Lower Triassic sections in Bogda Mountains, China, were measured at a cm-dm scale. 823 high-order fluvial-lacustrine cycles (HCs) have five major types, interpreted as basic time-stratigraphic units recording fluvial erosion-deposition and lake expansion-contraction. Facies and thickness stacking patterns of HCs define 137 intermediate-order and 17 low-order cycles (ICs and LCs). LCs and some ICs are correlative in 6 km; ICs and many HCs in 1-2 km; HCs in ~100 m. Lithofacies and thickness of HCs change over 10s-100s m. Three Kungurian Daheyan LCs of mainly braided-stream HCs filled topographic lows. Fluctuating profundal siliciclastic-carbonate HCs of Roadian Lucaogou LC thin westward into fluvial and littoral HCs. Fluvial and littoral HCs of Wordian Hongyanchi LC thin westward into dominantly littoral HCs. Eastward-thinning Capitanian Quanzijie LC of fluvial HCs overlies a major Calcisol, indicating a semi-arid-to-humid climate shift. Eastward-thickening Lopingian Wutonggou LC contains meandering-stream and deltaic HCs with Spodosols and Histosols indicating humid climate. Fluvial HCs with Calcisols of Induan Jiucaiyuan LC change eastward into littoral HCs, indicating a return to semi-arid climate. Olenekian Shaofanggou LC contains littoral HCs with Calcisols indicating stable tectonic and semi-arid conditions. Delineation and correlation of LCs and ICs, aided by interpreted lake-type, tectonic, and climatic trends, are critical to establishing a reliable sequence-stratigraphic framework for improved correlation of meter-scale HCs.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California