Abstract
Our understanding of reworked turbidites is still in its infancy, and their flow processes and genesis still remain understudied. Core data from the middle Miocene Zhujiang Formation in the Pearl River Mouth Basin allow us to differentiate reworked turbidites, yielding two main contributions. Firstly, reworked turbidites are distinguished from turbidites by the association of traction structures and tidal signatures, which occur in discrete units rather than forming a classic “Bouma Sequence” for turbidites. Sedimentological characteristics of reworked turbidites proposed here will help to obtain a robust set of diagnostic criteria for the recognition of deep-water non-turbidite deepwater units as reservoirs. Secondly, our results suggest that, in the down-slope direction, classic detritus carried in turbidity flows would synchronously be bidirectionally reworked by internal tides and waves, resulting in tidal signatures seen in the interpreted reworked turbidites. In the along-slope direction, upper parts of dilute turbidity currents would mix vertically with seawater, and muddy fines would be winnowed away by contour currents, whereas lower parts of dilute turbidity currents would probably drop their coarse particles, resulting in traction structures recognized in the documented reworked turbidites. Our work highlights the influence of bottom currents on the development and modification of turbidites and suggests that reworked turbidites were created by the combined action of down-slope transport and reworking and along-slope winnowing and sorting, helping to better understand flow processes and genesis of non-turbidite reservoirs with a great economic interest.
Original language | English |
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Pages (from-to) | 116-129 |
Number of pages | 14 |
Journal | Journal of Asian Earth Sciences |
Volume | 128 |
Early online date | 25 Jun 2016 |
DOIs | |
Publication status | Published - 1 Oct 2016 |
Bibliographical note
AcknowledgmentsAuthors are grateful to CNOOC for providing subsurface data and for allowing publication of this paper. We thank Kevin T. Pickering for taking the time to plough through an earlier version of this manuscript. We acknowledge interesting discussions with Jiwei Tian at the Ocean University of China on contour currents and internal tides and waves acting in the South China Sea. Authors are indebted to journal Editor (Mei-Fu Zhou) and reviewer for their critical but constructive comments that significantly improved this work, and to Shunli Li at China University of Petroleum (Beijing) for helping us draw Fig. 13. This study was jointly supported by the National Natural Science Foundation of China (Nos. 41372115 and 41302085). RioMAR sponsor companies are greatly acknowledged for their discussion and generous support of C. Gong’s postdoctoral research at the Jackson School of Geosciences of the University of Texas at Austin. Research was conducted in the framework of the “Drifters” Research Group of the Royal Holloway University of London (UK).
Keywords
- Reworked turbidites
- Bottom currents
- Turbidity flows
- Internal waves and tides
- Northern South China Sea margin