Effects of low- to high-angle normal faults on sedimentary architectures in the Eocene Wenchang Formation,Enping Sag,Pearl River Mouth Basin,South China Sea |
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| Authors: | Q H Liu Y Shu X M Zhu X H Yang M Tan |
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| Institution: | 1. College of Geosciences, China University of Petroleum, Beijing 102249, PR China;2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, PR China;3. China National Offshore Oil Corporation Limited-Shenzhen, Guangzhou 510240, PR China;4. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, PR China |
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| Abstract: | The effects of low- to high-angle (>30°) normal faults on sedimentary architectural units in the Eocene Wenchang Formation, Enping Sag, Pearl River Mouth Basin (PRMB), South China Sea were investigated utilising a high-quality 3D seismic data set and restored paleogeomorphology. It has been shown that sequence stratigraphic units and sedimentary architecture are significantly controlled by the low- to high-angle normal faults. The Wenchang Formation, a second-order sequence, can be subdivided into two para-second-sequences (the Lower and Upper Wenchang sequences, E2WL and E2WU) and seven third-order sequences (from base to top: SQ1～SQ7). The low-angle fault confined sequence architecture of the Wenchang Formation is mainly characterised by lateral stacking with the ratio of the vertical subsidence (V) to horizontal slip (H) being reduced from 1/2 for E2WL to 1/6 for E2WU. In contrast, the high-angle fault confined sequence is characterised by vertical stacking with the ratio of V/H close to 1 for sequences SQ1 to SQ7. In the 3D seismic area, the features of sediment-dispersal pattern were interpreted based on an integrated analysis of paleogeomorphology, seismic reflection characteristics, stratal thickness distribution and multiple attribute clustering. The results show that the large-scale fan delta, belt-shape lacustrine deposit and bird-foot braided delta systems mainly developed in the low-angle fault confined sequences, whereas small-scale fan delta, rhombus-shaped lacustrine deposit and lobe-shaped braided delta systems inherited tectono-sedimentary architectures in the high-angle fault confined sequences. |
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| Keywords: | normal faults seismic sequences sedimentary architecture Wenchang Formation Enping Sag South China Sea |
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