Evolution of Low-Angle Normal Faults in the Enping Sag, the Northern South China Sea: Lateral Growth and Vertical Rotation

Abstract

Low-angle normal faults (dip <30°, LANFs) are widespread in the northern margin of the South China Sea where the maximum crust thickness is approximately 30.0 km. Based on 3D seismic survey data and drilling wells in the Enping sag, evidences for LANFs that initially formed at high-angles are discussed. After a detailed investigation of extensional fault system and description of 3D fault geometry, the initial fault dips under the model of distributed vertical simple shear are also calculated. The results indicate that the present-day dip angles of the LANFs are in the range of 12° to 29°, and the initial fault dip angles are in the range of 39° to 49°. Deep seismic imaging suggests that the upper crust in the footwall block of the LANFs was tilted at an angle of ~14° to 22° due to the isostatic rebound during rifting. Moreover, the temporal and spatial sequences of the lateral growth of the LANFs have been investigated by the seismic interpretation of four isochronous stratigraphic interfaces, which demonstrates that two individual fault segments propagated towards each other and subsequently, were hard-linked during the Early Eocene.

Keywords

low-angle normal fault / fault rotation / fault growth / Enping sag / Pearl River Mouth Basin / the South China Sea

References

Anderson E M. The Dynamics of Faulting, 1951, 2nd Ed. Edinburgh: Oliver and Boyd, 206.

Axen G J. Karner G, Taylor B, Driscoll N. Mechanics of Low-Angle Normal Faults. Rheology and Deformation of the Lithosphere at Continental Margins, 2004 New York: Columbia University Press, 46-91.

Briais A, Patriat P, Tapponnier P. Updated Interpretation of Magnetic Anomalies and Seafloor Spreading Stages in the South China Sea: Implications for the Tertiary Tectonics of Southeast Asia. Journal of Geophysical Research: Solid Earth, 1993, 98(B4): 6299-6328.

Buck W R. Flexural Rotation of Normal Faults. Tectonics, 1988, 7(5): 959-973.

Cartwright J A, Mansfield C S. Lateral Displacement Variation and Lateral Tip Geometry of Normal Faults in the Canyonlands National Park, Utah. Journal of Structural Geology, 1998, 20(1): 3-19.

Childs C, Watterson J, Walsh J J. Fault Overlap Zones within Developing Normal Fault Systems. Journal of the Geological Society, 1995, 152(3): 535-549.

Collettini C. The Mechanical Paradox of Low-Angle Normal Faults: Current Understanding and Open Questions. Tectonophysics, 2011, 510(3/4): 253-268.

Davis D W, Sewell R J, Campbell S D G. U-Pb Dating of Mesozoic Igneous Rocks from Hong Kong. Journal of the Geological Society, 1997, 154(6): 1067-1076.

Dawers N H, Anders M H. Displacement-Length Scaling and Fault Linkage. Journal of Structural Geology, 1995, 17(5): 607-614.

Expedition 349 Scientists South China Sea Tectonics: Opening of the South China Sea and Its Implications for Southeast Asian Tectonics, Climates, and Deep Mantle Processes Since the Late Mesozoic, 2014, 349.

Fyhn M B W, Pedersen S A S, Boldreel L O, . Palaeocene-Early Eocene Inversion of the Phuquoc-Kampot Som Basin: SE Asian Deformation Associated with the Suturing of Luconia. Journal of the Geological Society, 2010, 167(2): 281-295.

Hall R. Cenozoic Geological and Plate Tectonic Evolution of SE Asia and the SW Pacific: Computer-Based Reconstructions, Model and Animations. Journal of Asian Earth Sciences, 2002, 20(4): 353-431.

Hall R. Late Jurassic-Cenozoic Reconstructions of the Indonesian Region and the Indian Ocean. Tectonophysics, 2012, 570/571: 1-41.

Holloway N. North Palwan Block, Philippines—Its Relation to Asian Mainland and Role in Evolution of South China Sea. American Association of Petroleum Geologists, 1982, 66(9): 1355-1383.

Huang C J, Zhou D, Sun Z, . Deep Crustal Structure of Baiyun Sag, Northern South China Sea Revealed from Deep Seismic Reflection Profile. Chinese Science Bulletin, 2005, 50(11): 1131-1138.

Jackson J A. Active Normal Faulting and Crustal Extension. Continental Extensional Tectonics, 1987, 28(1): 3-17.

Jahn B M, Chen P Y, Yen T P. Rb-Sr Ages of Granitic Rocks in Southeastern China and Their Tectonic Significance. Geological Society of America Bulletin, 1976, 87(5): 763-776.

Kapp P, Taylor M, Stockli D, . Development of Active Low-Angle Normal Fault Systems during Orogenic Collapse: Insight from Tibet. Geology, 2008, 36(1): 7-10.

Lecomte E, Jolivet L, Lacombe O, . Geometry and Kinematics of Mykonos Detachment, Cyclades, Greece: Evidence for Slip at Shallow Dip. Tectonics, 2010, 29(5): 1-22.

Lee T Y, Lawver L A. Cenozoic Plate Reconstruction of the South China Sea Region. Tectonophysics, 1994, 235(1/2): 149-180.

Leyla B H, Zhang J X, Yang L L. Quantitative Analysis of Faults in Huizhou Sub-Basin, Pearl River Mouth Basin. Journal of Earth Science, 2018, 29(1): 169-181.

Li P L, Liang H X, Dai Y D, . Origin and Tectonic Setting of the Yanshanian Igneous Rocks in the Pearl River Mouth Basin. Guangdong Geology, 1999, 14(1): 1-8.

Liu Q H, Zhu H T, Shu Y, . 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. Australian Journal of Earth Sciences, 2016, 63(7): 903-922.

Marchal D, Guiraud M, Rives T. Geometric and Morphologic Evolution of Normal Fault Planes and Traces from 2D to 4D Data. Journal of Structural Geology, 2003, 25(1): 135-158.

McClay K, Khalil S. Extensional Hard Linkages, Eastern Gulf of Suez, Egypt. Geology, 1998, 26(6): 563-566.

Morley C K. A Tectonic Model for the Tertiary Evolution of Strike-Slip Faults and Rift Basins in SE Asia. Tectonophysics, 2002, 347(4): 189-215.

Morley C K. Geometry and Evolution of Low-Angle Normal Faults (LANF) within a Cenozoic High-Angle Rift System, Thailand: Implications for Sedimentology and the Mechanisms of LANF Development. Tectonics, 2009, 28(5): 1-30.

Morley C K. Late Cretaceous-Early Palaeogene Tectonic Development of SE Asia. Earth-Science Reviews, 2012, 115(1/2): 37-75.

Morley C K. The Widespread Occurrence of Low-Angle Normal Faults in a Rift Setting: Review of Examples from Thailand, and Implications for Their Origin and Evolution. Earth-Science Reviews, 2014, 133(2): 18-42.

Nguyen T, Satir M, Siebel W, . Granitoids in the Dalat Zone, Southern Vietnam: Age Constraints on Magmatism and Regional Geological Implications. International Journal of Earth Sciences, 2004, 93(3): 329-340.

Nissen S S, Hayes D E, Buhl P, . Deep Penetration Seismic Soundings Across the Northern Margin of the South China Sea. Journal of Geophysical Research: Solid Earth, 1995, 100(B11): 22407-22433.

Proffett J M. Cenozoic Geology of the Yerington District, Nevada, and Implications for the Nature and Origin of Basin and Range Faulting. Geological Society of America Bulletin, 1977, 88(2): 247-266.

Rotevatn A, Fossen H, Hesthammer J, . Are Relay Ramps Conduits for Fluid Flow? Structural Analysis of a Relay Ramp in Arches National Park, Utah. Geological Society, London, Special Publications, 2007, 270(1): 55-71.

Ru K, Pigott J D. Episodic Rifting and Subsidence in the South China Sea. American Association of Petroleum Geologists Bulletin, 1986, 70(9): 1136-1155.

Schlüter H U, Hinz K, Block M. Tectono-Stratigraphic Terranes and Detachment Faulting of the South China Sea and Sulu Sea. Marine Geology, 1996, 130(1/2): 39-78.

Sewell R J, Campbell S D G. Geochemistry of Coeval Mesozoic Plutonic and Volcanic Suites in Hong Kong. Journal of the Geological Society, 1997, 154(6): 1053-1066.

Smith S A F, Faulkner D R. Laboratory Measurements of the Frictional Properties of the Zuccale Low-Angle Normal Fault, Elba Island, Italy. Journal of Geophysical Research, 2010, 115(B2): 1-17.

Smith S A F, Holdsworth R E, Collettini C, . Using Footwall Structures to Constrain the Evolution of Low-Angle Normal Faults. Journal of the Geological Society, 2007, 164(6): 1187-1191.

Soliva R, Benedicto A. A Linkage Criterion for Segmented Normal Faults. Journal of Structural Geology, 2004, 26(12): 2251-2267.

Tapponnier P, Peltzer G, Armijo R. Coward M P, Ries A C. On the Mechanics of the Collision between India and Asia. Collision Tectonics, 1986 London: Geological Society, Special Publications, 115-157.

Taylor B, Hayes D E. Hayes D E. Origin and History of the South China Sea Basin. The Tectonic and Geologic Evolution of Southeast Asia Seas Islands: Part 2, 1983, 23-56.

Taylor S K, Bull J M, Lamarche G, . Normal Fault Growth and Linkage in the Whakatane Graben, New Zealand, during the last 1.3 Myr. Journal of Geophysical Research: Solid Earth, 2004, 109(B2): 1-22.

Thuy N T B, Satir M, Siebel W, . Geochemical and Isotopic Constraints on the Petrogenesis of Granitoids from the Dalat Zone, Southern Vietnam. Journal of Asian Earth Sciences, 2004, 23(4): 467-482.

Trudgill B, Cartwright J. Relay-Ramp Forms and Normal-Fault Linkages, Canyonlands National Park, Utah. Geological Society of America Bulletin, 1994, 106(9): 1143-1157.

Walsh J J, Bailey W R, Childs C, . Formation of Segmented Normal Faults: A 3-D Perspective. Journal of Structural Geology, 2003, 25(8): 1251-1262.

Wang X Y, Yang Z, Chen N S, . Petrogenesis and Ore Genesis of the Late Yanshanian Granites and Associated Porphyry-Skarn W-Mo Deposits from the Yunkai Area of South China: Evidence from the Zircon U-Pb Ages, Hf Isotopes and Sulfide S-Fe Isotopes. Journal of Earth Science, 2018, 29(4): 939-959.

Wernicke B. Low-Angle Normal Faults and Seismicity: A Review. Journal of Geophysical Research: Solid Earth, 1995, 100(B10): 20159-20174.

Wernicke B, Axen G J. On the Role of Isostasy in the Evolution of Normal Fault Systems. Geology, 1988, 16(9): 848-851.

Wernicke B, Walker J D, Beaufait M S. Structural Discordance between Neogene Detachments and Frontal Sevier Thrusts, Central Mormon Mountains, Southern Nevada. Tectonics, 1985, 4(2): 213-246.

Westaway R. The Mechanical Feasibility of Low-Angle Normal Faulting. Tectonophysics, 1999, 308(4): 407-443.

Westaway R. Active Low-Angle Normal Faulting in the Woodlark Extensional Province, Papua New Guinea: A Physical Model. Tectonics, 2005, 24(6): 1-25.

Westaway R, Kusznir N. Fault and Bed ‘Rotation’ during Continental Extension: Block Rotation or Vertical Shear?. Journal of Structural Geology, 1993, 15(6): 753-770.

Whitney D L, Teyssier C, Rey P, . Continental and Oceanic Core Complexes. Geological Society of America Bulletin, 2013, 125(3/4): 273-298.

Willemse E J M. Segmented Normal Faults: Correspondence between Three-Dimensional Mechanical Models and Field Data. Journal of Geophysical Research: Solid Earth, 1997, 102(B1): 675-692.

Xu C H, Shi H S, Barnes C G, . Tracing a Late Mesozoic Magmatic Arc along the Southeast Asian Margin from the Granitoids Drilled from the Northern South China Sea. International Geology Review, 2016, 58(1): 71-94.

Yan Q S, Shi X F, Li N S. Oxygen and Lead Isotope Characteristics of Granitic Rocks from the Nansha Block (South China Sea): Implications for Their Petrogenesis and Tectonic Affinity. Island Arc, 2011, 20(2): 150-159.

Yan Q S, Shi X F, Castillo P R. The Late Mesozoic-Cenozoic Tectonic Evolution of the South China Sea: A Petrologic Perspective. Journal of Asian Earth Sciences, 2014, 85: 178-201.

Ye Q, Mei L F, Shi H S, . A Low-Angle Normal Fault and Basement Structures within the Enping Sag, Pearl River Mouth Basin: Insights into Late Mesozoic to Early Cenozoic Tectonic Evolution of the South China Sea Area. Tectonophysics, 2018, 731/732: 1-16.

Zahirovic S, Seton M, Müller R D. The Cretaceous and Cenozoic Tectonic Evolution of Southeast Asia. Solid Earth, 2014, 5(1): 227-273.

Zhou D, Ru K, Chen H Z. Kinematics of Cenozoic Extension on the South China Sea Continental Margin and Its Implications for the Tectonic Evolution of the Region. Tectonophysics, 1995, 251(1/2/3/4): 161-177.

Zhou D, Yao B C. Tectonics and Sedimentary Basins of the South China Sea: Challenges and Progresses. Journal of Earth Science, 2009, 20(1): 1-12.