||Taiwan had been a passive continental margin from the middle Oligocene to late Miocene. There were two local extensional events, leading to the formation of small rifted basins during the passive-margin stage. In order to establish a comprehensive sequence stratigraphic framework, we use well-log data of 11 boreholes near the B Fault and Yichu Fault in SW Taiwan for paleo-environmental and sequence stratigraphic analyses. The well data was provided by CPC Corporation. |
Eight sedimentary facies and 8 types of parasequences are identified. Our results shows that Pachangchi Sandstone was accumulated in the shoreface environment. The overlying formations (i.e., Piling Shale to Talu Shale) exhibit offshore to shoreface environments. During the deposition of the Kuanyinshan Sandstone and the Nanchuang Formation, the environment changed into a tide-and-wave-dominated environment, consisting of tidal deposits, barrier complexes and shoreface deposits. For the sequence stratigraphic analysis, the Miocene strata is divided into 14 sequences, namely, K0, M0, M2, M4, M6, M8, M10, M12+M14, M16, M18, M20, M22, M24 and M26, in an ascending order.
According to borehole stratigraphic correlations and sequence stratigraphic analyses, we found that the thickness of the Pachangchi Sandstone and its equivalents at KTL-3 well is quite thick, up to around 400 m. While the thickness of the Pachangchi Sandstone in the rest of studied borehole is only 60 m to 100 m. Similarly, the thickness of Nanchuang Formation attains up to about 1200 m at HSY-1 well. Base on this observation and previous study, we divided the tectonic activity in this region into 3 stages. (1) K0, M0, M2 sequences (early post break up, 30~21 Ma): Yichu Fault became active and created a half graben as observed at KTL-3 well. Sequences of K0, M0 and M2 were deposited. (2) M4~M18 sequence (21~12.5 Ma, thermal subsidence): Thickness of each formation and sequence remains consistent, no major tectonic activities in this period. Sequences of M4~M18 were accumulated during this period (3) M20~M26 sequences (12.5~6.5 Ma, renewed extension): Yichu Fault and B Fault became active, leading to the formation of a graben as seen at the JY-1 well, while the area near northern B Fault became an uplifted platform. Sequences of M20~M26 were deposited.
Allen, D. R. (1975). Chapter 7 Identification of Sediments - Their Depositional Environment and Degree of Compaction—from Well Logs Developments in Sedimentology (Vol. 18, pp. 349-401): Elsevier.
Biq, C.-C. (1972). Dual-trench structure in the Taiwan-Luzon region Proceedings of the Geological Society of China, 15, 65-75.
Cant, D. (1992). Subsurface Facies Analysis. In: Facies Model, Response to sea level change. Paper presented at the Geological Association of Canada.
Catuneanu, O. (2006). Principles of Sequence Stratigraphy: Elsevier.
Chai, B. H. T. (1972). Structure and tectonic evolution of Taiwan. American Journal of Science, 272, 389-422.
Chou, J.-T. (1975). A sedimentologic study of the Miocene Pachangchi Sandstone in the Chiayi region, western Taiwan. Petroleum Geology of Taiwan, 12, 81-96.
Chou, J.-T. (1980). Stratigraphy and sedimentology of the Miocene in western Taiwan. Petroleum Geology of Taiwan, 17, 33-52.
Chow, J. J., Li, M. C., and Fuh, S. C. (2005). Geophysical well log study on the paleoenvironment of the hydrocarbon producing zones in the Erchungchi formation, Hsinyin, SW Taiwan. Terrestrial Atmospheric and Oceanic Sciences, 16, 531-545.
Galloway, W. (1989). Genetic stratigraphic sequences in basin analysis I: Architecture and genesis of flooding-surface bounded depositional units. AAPG Bulletin, 73,125-142
Haq, B., Hardenbol, J. R., and Vail, P. (1987). Chronology of Fluctuating Sea Levels Since the Triassic. Science, 235, 1156-1167.
Heezen, B. C. (1974). Atlantic-type continental margins. In C. A. Burk & C. L. Drake (Eds.), The Geology of Continental Margins (pp. 13-24). Berlin, Heidelberg: Springer Berlin Heidelberg.
Hsieh, S.-H. (1965). The sandstone reservoirs in the lower Miocene Piling Shale in the Miaoli area, Taiwan. Petroleum Geology of Taiwan, 4, 187-200.
Lin, A., and Watts, A. (2002). Origin of the West Taiwan Basin by orogenic loading and flexure of a rifted continental margin. Journal of Geophysical Research, 107.
Lin, A. T.-S. (2001). Cenozoic Stratigraphy and Tectonic Development of the West Taiwan Basins. (Ph.D.), University of Oxford, Oxford, UK.
Lin, A. T., Watts, A., and Hesselbo, S. (2003). Cenozoic stratigraphy and subsidence history of the South China Sea margin in the Taiwan region. Basin Research, 15, 453-478.
Lin, A. T., Yang, C.-C., Wang, M.-H., and Wu, J.-C. (2021). Oligocene-Miocene sequence stratigraphy in the northern margin of the South China Sea: An example from Taiwan. Journal of Asian Earth Sciences, 213, 104765.
Noel, P. J., and Robert, W. D. (2010). Facies models 4: Geological Association of Canada.
Posamentier, H. W., and Vail, P. (1988). Eustatic controls on clastic deposition. II. Sequence and Systems Tract Models. In: Wilgus, C.K., Hastings, B.S., Kendall, C.G.St.C., Posamentier, H.W., Ross, C.A., Van Wagoner, J.C.(ed)., Sea Level Changes—An Integrated Approach, Vol. 42. SEPM Special Publication, 125-154.
Rider, M. H. (1996). The Geological Interpretation of Well Logs: Second Edition: Houston, Texas: Gulf Publishing.
Roy, P. S., Thom, B. G., and Wright, L. D. (1980). Holocene sequences on an embayed high-energy coast: an evolutionary model. Sedimentary Geology, 26(1), 1-19.
Selley, R. C. (1998). Elements of Petroleum Geology: Second Edition: Academic Press.
Serra, O. (1989). Sedimentary Environments from Wireline Logs. Schlumberger Technical Services, 243.
Siddiqui, N., Abd Rahman, A. H., Sum, C., Yusoff, W. I., and Ismail, M. (2017). Shallow-marine sandstone reservoirs, depositional environments, stratigraphic characteristics and facies model: A review. Journal of Applied Sciences, 17, 212-237.
Tang, C.-H. (1971). tratigraphical relation of the Talu Shale to the Peiliao Formation in northwest Taiwan. Petroleum Geology of Taiwan, 8, 175-186.
Teng, L. S. (1990). Geotectonic evolution of late Cenozoic arc-continent collision in Taiwan. Tectonophysics, 183, 57-56.
Wagoner, J. C., Mitchum, R. M., Campion, K., and Rahmanian, V. D. (1990). Siliciclastic Sequence Stratigraphy in Well Logs, Cores and Outcrops:Concepts for High-resolution Correlation of Time and Facies. American Association of Petroleum Geologists Methods in Exploration Series(Vol. 7, pp. 1-55).
Yielding, G., and Roberts, A. (1992). Footwall uplift during normal faulting — implications for structural geometries in the North Sea. In R. M. Larsen, H. Brekke, B. T. Larsen, & E. Talleraas (Eds.), Structural and Tectonic Modelling and its Application to Petroleum Geology (Vol. 1, pp. 289-304). Amsterdam: Elsevier.