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Characteristics and origins of ridges and troughs on the top of the middle Miocene strata in the Beijiao Sag of the Qiongdongnan Basin, northern South China Sea

Li Yufeng, Pu Renhai, Zhang Gongcheng and Qu Hongjun
Characteristics and origins of ridges and troughs on the top of the middle Miocene strata in the Beijiao Sag of the Qiongdongnan Basin, northern South China Sea
Interpretation (Tulsa) (May 2021) 9 (2): SB1-SB15

Abstract

Sedimentary structures generated by (deepwater) bottom currents are of interest to geologists. Based on the root mean square, coherence attribute, and 3D representations, ridges and troughs are imaged for the first time using 3D high-resolution seismic data and confirmed by a well, YL19-1-1, in the Beijiao Sag of the Qiongdongnan Basin. Combined with 2D seismic profiles, we define the flow direction of bottom currents resulting in ridges and troughs. The results indicate that ridges and troughs occur on the top of the Middle Miocene strata and dominantly present wave-shaped structures. Their magnitudes decrease toward the upper and lower slopes. They extend for tens of kilometers, dominantly parallel to one another, with an evenly spaced distribution, some of which locally merge and bifurcate. They are aligned obliquely to the regional slope. The internal ridges are characterized by internal mounded reflections and/or parallel underlying-strata reflections. The presence of polygonal faults and weak to moderate amplitudes within the ridges and troughs suggests that they consist of fine-grained mudstones, as confirmed by the well YL19-1-1. High amplitudes filled within troughs are probably composed of coarse-grained turbidite materials, where polygonal faults are inhibited. Truncations and onlaps occur along the thalweg of a trough and are also clearly observed on the flanks of ridges and the walls of troughs. We infer that the troughs are a product of the erosion of bottom currents and the ridges are remnant underlying (sediment waves) strata as a result of the redeposition of eroded sediments. In addition, troughs are filled by turbidite materials with high amplitudes in the southwestern area of the 3D seismic survey, where ridges and troughs are a combined result of the early erosion by bottom currents and the later reworking by turbidity flows. We have developed conceptual schematic models to indicate the evolutionary history of the ridges and troughs. It provides new insights into the further understanding of the erosional and depositional impacts of bottom currents.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 9
Serial Issue: 2
Title: Characteristics and origins of ridges and troughs on the top of the middle Miocene strata in the Beijiao Sag of the Qiongdongnan Basin, northern South China Sea
Affiliation: Southwest University of Science and Technology, School of Environment and Resources, Mianyang, China
Pages: SB1-SB15
Published: 202105
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 37
Accession Number: 2022-004676
Categories: Applied geophysicsStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Part of a special issue entitled Seismic interpretation of contourites and deepwater sediment waves, edited by Dunlap, D.
Illustration Description: illus. incl. sects., sketch maps
N16°45'00" - N17°19'60", E110°40'00" - E112°00'00"
Secondary Affiliation: Northwest University, CHN, ChinaChina National Offshore Oil Corporation, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute.
Update Code: 2022
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