Biostratigraphic and Geological Changes of Nanofossils on the Fault Surface During the Volcanic Mudflow Era in the Guanmiao District from Tainan to Kaohsiung and Its Significance

Resumen

The lithofacies differ significantly in the western part of Taiwan, especially in the south of Tzenwenchi. Therefore, stratigraphic correlation cannot rely solely on lithofacies but rather must rely on fossils. Due to calcareous nannofossils are very rich in the sediments of western Taiwan, not only the ages of formations can be determined, but also the stratigraphic relationship between the south-north can be understood. Samples collected from the eastern and western Kuanmiao sections have been studied on the basis of the calcareous nannofossil analysis. A total of six calcareous nannofossil zones were established in terms of the index fossils associated with important assemblages. These fossil zones included the upper Miocene Discoaster quinqueramus zone, the lower Pliocene Ceratolithus acutus zone, the Reticulofenestra pseudoumbilica zone, the upper Pliocene Cyclococcolithina macintyrei zone, the Pleistocene Pseudoemiliania lacunosa zone, and the Gephyrocapsa oceanica zone. Among them, the Pseudoemiliania lacunosa Zone could be subdivided into three subzones, namely, the Coccolithus doronicoides subzone, the small Gephyrocapsa subzone, and the Pseudoemiliania lacunosa subzone. These zones not only could be correlated with those of the Tzenwenchi section in Tainan and with those in the Chishan section of the Kaohsiung, but also with the zones in the Chuhuangkeng section of the Miaoli area.Nannofossils were also studied from the mud flows of mud volcanos located in the Tainan-Kaohsiung foothills. The ages of mudflow source beds are not entirely related to the seating outcropped formations. The nannofossil assemblages on the mud flows are mainly composed of two groups: the upper Miocene zone (NN-11), the age interred between 5.6~7.0 m.y. and the lower Pliocene zone (NN-12~ NN-15), the age interred between 5.0~3.5 m.y. The other mud volcanoes (KMV, TMV and LMV) are seated on the recent deposits. The mud volcano LMV is the one that only contains the Pleistocene zone (NN19) nannofossils among the studied mud volcanoes, the age interred 2.588 m.y. It can be said that it has a very high research value of nano-fossils