--> Abstract: Wither Nonmarine Sequence Stratigraphy? Sequence Stratigraphic Correlation of Lower Permian Fluvial-Lacustrine Deposits in a Half Graben, Bogda Mountains, NW China, by W. Yang, Q. Feng, Y. Liu, J. Lin, and W. Guan; #90090 (2009).
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Wither Nonmarine Sequence Stratigraphy? Sequence Stratigraphic Correlation of Lower Permian Fluvial-Lacustrine Deposits in a Half Graben, Bogda Mountains, NW China

Yang, Wan 1; Feng, Qiao 2; Liu, Yiqun 3; Lin, Jinyan 3; Guan, Wei 1
1 Department of Geology, Wichita State University, Wichita, KS.
2 College of Geoinformatics, Shangdong University of Science and Technology, Qingdao, China.
3 Department of Geology, Northwestern University, Xi'an, China.

Rapid facies and thickness changes in fluvial-lacustrine strata demand but also challenge the application of sequence stratigraphic concepts and principles in stratigraphic correlation. Such an application was tested for Lower-Permian Lucaogou low-order cycle in an 88-km2 area, southern Bogda Mountains, NW China, to identify effective criteria and procedures. The Lucaogou has a transgressive base on alluvial-fan deposits and a fluvial erosional top. Primary high-order cycles (HCs) composed of fluvial-lacustrine siliciclastics, carbonates, and paleosols at a scale of 0.1-1 m reflect systematic changes of stream, littoral, to profundal environments, indicating lake expansion and contraction. They were grouped into Previous HitsystemsNext Hit Previous HittractsNext Hit and sequences on the basis of stacking patterns of depositional environments and cycle thickness. Lake type, climate, and tectonic movement of provenance and depositional site were interpreted from paleosols, lithology, and depositional environment. 7 sections measured at a cm-dm scale are 0.1 - 4 km apart. 4 long sections are 98, 181, 197, and 88 m thick and contain 66/18, 135/30, 145/41, and 44/11 HCs/sequences. 3 short sections at basal Lucaogou are each ~12 m thick with 28/3, 13/3, 8/1 HCs/sequences. HCs, Previous HitsystemsNext Hit Previous HittractsNext Hit, and sequences are correlative in stacking patterns of cycle thickness, component lithofacies, and interpreted environments among sections 100s-m apart. However, all HCs and most Previous HitsystemsNext Hit Previous HittractsNext Hit cannot be correlated in >2 km distance due to drastic changes of lithofacies, thickness, and environments, and cycle amalgamation and absence. Correlation of sequences is successful through an iterative process, mainly based on interpreted climatic and tectonic trends and speculated sedimentary processes corresponding to different lake Previous HittypesNext Hit. As a result, basin-filling history at the center and steep and ramp margins of the half graben were reconstructed at a Previous HitsystemsNext Hit Previous HittractsTop and sequence scale. Sequence stratigraphic grouping of HCs facilitated interpretation of various controlling processes. The same regional processes produced different HCs and sequences at different parts of the graben because of variable boundary conditions. Thus, a process-response approach in sequence stratigraphic correlation utilizing trends of regionally persistent processes may be effective. The key is accurate interpretation of mixed controlling processes, which can be improved by studying modern analogs.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009