Oligocene–Miocene carbonates in the Reed Bank area, South China Sea, and their tectono-sedimentary evolution

Abstract

We have analyzed two recently acquired multichannel seismic profiles across the Reed Bank area, South China Sea. A detailed seismic interpretation coupled with drilling data has proved the occurrence of a wide carbonate platform, developed between the Late Oligocene and the Early Miocene (32-20 Ma). The top of these carbonates is an important regional unconformity, corresponding to a strong and continuous seismic reflector. An age of about 20 Ma is inferred for this reflector, acting as a regional unconformity marking the cessation of seafloor spreading with an erosional/non-depositional hiatus, spanning 3 or 4 m.y. The time interval during which the carbonate platforms formed is concurrent with the opening of the South China Sea. The reconstruction of the tectonic subsidence in this area has shown a decrease in rate of subsidence during the drifting stage (32-17 Ma), indicating that the whole Reed Bank area was in a tectonically stable and shallow water environment for more than 10 m.y., favoring the development of shallow water carbonates. With a sharply increased subsidence rate after the end of spreading (17 Ma) and a continuously increased sea level, the carbonate platforms were drowned and died, except some structural highs with reef buildups, where the carbonate sedimentation continued to Middle Miocene. We suggest that delayed tectonic subsidence in Reed Bank area might have been related to a secondary mantle convection under the rift lasting more than about 10 m.y.

Sedimentary budget of the Southwest Sub‐basin, South China Sea: Controlling factors and geological implications

“…Carbonate deposits, including carbonate platform and coral reef on the top of the basement highs, were well developed in both the southern and northern continental margins in the SCS since the Late Oligocene (Ding et al, ; Ding, Li, Dong, & Fang, ; Ma et al, ; Wu, Zhao, & Dong, ; Xie, Zhang, & Ren, ). Although most carbonate platforms were drowned since the Middle Miocene, the reefs on the basement highs could continue their growth even to the Late Miocene (Steuer et al, ), which was transported into the abyssal basin and formed thick carbonate interlayers in the clay or silty clay in the SWSB, with a thickness of 1m.…”

Cretaceous–Palaeogene sedimentary evolution of the South China Sea region: A preliminary synthesis

“…During the rifting period, numerous NE–SW‐trending half‐grabens and rotated blocks were developed, resulting in the formation of a series of large and deep Cenozoic sedimentary basins (e.g., Reed Bank and Beikang‐Nanweixi‐Wan'an basins) fringing the waters and several small basins in the central part (Ding, Franke, Li, & Steuer, ; Taylor & Hayes, ; Tong, Ren, Liao, Yao, & Zhao, ; P. Yan & Liu, ). The syn‐rift strata are mainly composed by fluvial to neritic interbeds of siltstones and sandstones of Late Eocene to Oligocene age (Figure ), which are regionally blanketed by widespread Late Oligocene to Early Miocene carbonate platforms extending from the Dangerous Grounds eastward to the Palawan shelf and also outcropping in Palawan as Nido Limestone (Aurelio et al, ; Ding, Li, Dong, & Fang, ; Steuer et al, ; Tong et al, ).…”

“…Yan & Liu, 2004). The syn-rift strata are mainly composed by fluvial to neritic interbeds of siltstones and sandstones of Late Eocene to Oligocene age (Figure 4), which are regionally blanketed by widespread Late Oligocene to Early Miocene carbonate platforms extending from the Dangerous Grounds eastward to the Palawan shelf and also outcropping in Palawan as Nido Limestone (Aurelio et al, 2014;Ding, Li, Dong, & Fang, 2014;Steuer et al, 2014;Tong et al, 2019). As sedimentary lithofacies are intended to be presented in the palinspastic reconstructions in order to illustrate the in situ sedimentary evolution concurrent with and prior to the South China Sea formation, some critical palaeogeographic hypotheses need to be carefully and reasonably made before presenting the results.…”

Oceanic mantle gravimetric response to the seafloor spreading of the Southwest Sub‐basin, South China Sea

“…Altogether, we employed 10 seismic profiles transecting the study region in SWSB (refer to Supporting Information for MCS detail) to re-interpret profiles in light of the result of IODP expedition 349 drilling hole U1433B. In general, eight MCS profiles (four green, two white and two orange dashed lines in Figure 1) were acquired by M/V TANBAO of Guangzhou Marine Geology Survey with a 480-channel streamer recorded at a sample rate of 2 ms; the detailed images of the seismic profiles can be found in several other papers (Li et al, 2012;Ding et al, 2015;Ding et al, 2016). Another two MCS profiles (SO49-22 and SO49-23 in thin dashed lines) were acquired during the 'Joint Sino-German SONNE 49 Cruise' in 1987 with a 48-channel streamer recorded at a sample rate of 4 ms, and its detailed interpretation could be found in other research papers as well (Franke et al, 2011;Li et al, 2012;Franke et al, 2014).…”