Depositional evolution of sediment drifts inside intra-slope basins on the lower southeastern slope of the Dongsha Islands (South China Sea) and their paleoceanographic implications
- 32 Downloads
Confined drifts generally contain abundant paleoceanographic information. The lower southeastern slope of the Dongsha Islands, South China Sea, was partly disassembled into several intra-slope basins by igneous bodies formed during the post-spreading process. Based on a series of high-resolution, two-dimensional seismic profiles, this study presents seismic evidence of sediment drifts inside several intra-slope basins at present water depths between approximately 2100 and 2800 m. The main discontinuities in the study area since the middle Miocene were carefully correlated with nearby seismic lines reported by previous studies. Moreover, their accurate ages were determined according to the dating results of the China National Offshore Oil Corporation with microfossil combinations. From 15.97 to 7.16 Ma, sheeted drifts were formed near the obstacles, indicating fairly low-velocity bottom currents. Subsequently, low-relief mounded drifts and associated small-scale moats were formed along the obstacles (7.16–5.33 Ma), showing that bottom currents were relatively strong. From 5.33 Ma onwards, high-relief mounded drifts and associated large-scale moats prevailed, formed by intensified bottom currents. Additionally, high-relief mounded drifts associated with large-scale moats occurred near the northern obstacle, and low-relief mounded drifts and associated small-scale moats were only formed near the southern obstacle in the largest intra-slope basin. In contrast, in the narrowest intra-slope basin, high-relief mounded drifts were confined by large-scale moats at the foot of both obstacles. This stark difference is attributed to the lateral variation of bottom current intensities caused by the variable widths of the intra-slope basins, resulting in different confining effects on bottom currents. The changes recorded in the sediment drifts reveal that the sedimentary succession should be subdivided into three phases: the onset stage (15.97–7.16 Ma), the slow growth stage (7.16–5.33 Ma), and the rapid growth stage (since 5.33 Ma). The gradual intensification of bottom currents is closely related to the influx of the Northern Pacific Deep Water since ~ 7 Ma and the gradual formation of the semi-enclosed environment due to the eastward subduction of the South China Sea basin into the Philippine plate since the late Miocene.
Firstly, we would like to acknowledge the Guangzhou Marine Geological Survey for providing the high-resolution, multichannel 2D seismic data. The authors also express their appreciations for the help provided by colleagues of the Guangzhou Marine Geologic Survey and Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences. Two reviewers are also thanked for their constructive comments and suggestions.
The study was supported by the National Natural Science Foundation of China (Nos. 91528301, 41606074, and 41502102).
- Chen CTA (2005) Tracing tropical and intermediate waters from the South China Sea to the Okinawa Trough and beyond. J Geophys Res 110:C05012Google Scholar
- Faugères JC, Stow DAV (2008) Chapter 14 contourite drifts: nature, evolution and controls. Developments in Sedimentology 60:257, 259–288Google Scholar
- Gong ZS, Jin Q, Qiu Z, Wang S, Meng J (1989) Geology, tectonics and evolution of the Pearl River Mouth Basin. Chinese Sedimentary Basins. Elsevier, Amsterdam, pp 181–196Google Scholar
- Gruetzner J, Uenzelmann-Neben G (2015) Contourite drifts as indicators of Cenozoic bottom water intensity in the eastern Agulhas Ridge area, South Atlantic Mar Geol 378:350–360Google Scholar
- Hernández-Molina FJ, Sierro FJ, Llave E, Roque C, Stow DAV, Williams T, Lofi J, Schee VD, Arnáiz A, Ledesma S, Rosales C, Rodríguez-Tovar FJ, Pardo-Igúzquiza E, Brackenridge RE (2016) Evolution of the gulf of Cadiz margin and southwest Portugal contourite depositional system: tectonic, sedimentary and paleoceanographic implications from IODP expedition 339. Mar Geol 377:7–39CrossRefGoogle Scholar
- Huang CY, Yuan PB, Lin CW, Wang TK, Chang CP (2000) Geodynamic processes of Taiwan arc-continent collision and comparison with analogs in Timor, Papua New Guinea, Urals and Corsica. Tectonophysics 325:1–21Google Scholar
- Li QY, Zhao QH, Zhong GF, Jian ZM, Tian J, Cheng XR, Wang PX, Chen MH (2008) Deep water ventilation and stratification in the Neogene South China Sea. JES 33:1–11Google Scholar
- Luan XW, Wang K, Wei XY, Shi YF, Zhang H (2018) New interpretation for the main sediment source of the rapidly deposited sediment drifts on the northern slope of the South China Sea. J Asian Earth Sci (accepted manuscript)Google Scholar
- Pang X, Chen CM, Peng DJ, Zhou D, Shao L, He M, Liu BJ (2008) Basic geology of Baiyun deep-water area in the northern South China Sea. COOG 20:16–222 (in Chinese with English abstract)Google Scholar
- Qu TD, Girton JB, Whitehead JA (2006) Deepwater overflow through Luzon Strait. J Geophys Res-Oceans 111(C1)Google Scholar
- Rebesco M, Özmaral A, Urgeles R, Accettella D, Lucchi RG, Rüther D, Winsborrow M, Llopart J, Caburlotto A, Lantzsch H, Hanebuth TJJ (2016) Evolution of a high-latitude sediment drift inside a glacially-carved trough based on high-resolution seismic stratigraphy (Kveithola, NW Barents Sea). Quat Sci Rev 147:178–193CrossRefGoogle Scholar
- Shao L, Li X, Wang PX, Jian Z, Wei G, Pang X, Liu Y (2004) Sedimentary record of the tectonic evolution of the South China Sea since the Oligocene-evidence from deep sea sediments of ODP Site 1148. Adv Earth Science 19:539–544Google Scholar
- Su NR, Zeng L, Li PL (1995) Geological features of Mesozoic sags in the eastern part of Pearl River mouth basin. COOG 9(4):228–236 (in Chinese with English abstract)Google Scholar
- Sun M, Ren JF, Zhong GJ, Yi H (2018) Fold deformations of Mesozoic strata and their genetic mechanism in southwestern Dongsha waters of northern South China Sea. Geological Review 64(4):828–842 (in Chinese with English abstract)Google Scholar
- Wang H (2007) Sedimentation processes and its response in deepwater environment of the northern continental margin, the South China Sea. CUPB pp. 1–131 (doctoral dissertation)Google Scholar
- Wang PX, Li QY (2009) Oceanographical and Geological Background. In: Oceanographical and Geological background of the South China Sea. Springer, Netherlands, pp 25–73Google Scholar
- Xu S, Wang YM, He M, Du JY, Xu GQ, Chen WT, Wei WJ, Chen C (2016) Slope types and their controlling effects on deep-water reservoir in the Pearl River Mouth basin. Journal of China University of Mining & Technology 45:982–992 (in Chinese with English abstractGoogle Scholar
- Zhao QH, Li QY, Jian ZM (2009) Deep waters and oceanic connection. DPR 13:395–437Google Scholar