Middle Miocene Paleoceanography of the Niigata oil field, northern Japan, based on calcareous nannofossils

Abstract

We studied in detail the middle Miocene NN5 and NN6 calcareous nannofossil assemblages of the Nanatani Formation for reconstruction of the paleoceanography of the Niigata oil field.The wide area located in the Niigata plain from Mitsuke to Yahiko-Teradomari is interpreted as an area of non-marine paleoenvironments during the deposition of the NN5 to NN6 zones, which is consistent with the previous seismic stratigraphic interpretation.In addition, abundant NN5 calcareous nannofossils related to the main ocean current system are found in the area from the southeast to northeast along the Shibata-Koide tectonic line. The abundance decreased in the NN6 zone, which was paralleled with the shrinkage of the marine area within the Niigata basin. The timing of this environmental change between the NN5/NN6 is correlated to a cooling event shown by Holbourn et al. (2013) just after the Mid-Miocene Climatic Optimum, and hence the fall of the global sea level. This indicates that the environment changes in the late Nanatani Age were strongly influenced by the middle Miocene global climatic event.Furthermore, the NN5 and NN6 calcareous nannofossils are absent in the oil and gas fields, which are characterized by Miocene volcanic reservoirs. This evidences that the topographic relieves around the oil and gas fields today already existed prior to the time of the deposition of the NN5 zone. This suggests that the general framework of the oil and gas-bearing structures would have been established as a consequence of the rifting and rift-related volcanism during the opening of the Japan Sea.

Figure 6 from: Farida M, Jaya A, Ahmad A, Nugraha J (2024) The Eocene to Oligocene boundary and paleoclimatic indications based on calcareous nannofossils of Tonasa Formation, South Sulawesi, Indonesia. Fossil Record 27(1): 221-231. https://doi.org/10.3897/fr.27.e96985

“…High-resolution biostratigraphy with nannofossils can provide the ages of rocks with higher precision and is one of the most powerful biostratigraphical tools in carbonate sediments (Agnini et al 2017). This applies also to the investigation of the paleoenvironment, paleoclimate, paleoceanography, and other aspects (Perch-Nielsen 1985;Persico and Villa 2004;De Vargas et al 2007;Villa et al 2008;Ali 2009;Sato and Chiyonobu 2009). The biozonation of calcareous nannofossils during the Paleogene has been proposed by some authors.…”

“…One of the most important components of carbonate rock is nannofossils, which were primary producers. They are useful as a tool for determining the biostratigraphy, paleoceanography, and paleoclimate of marine sediments (Perch-Nielsen 1985;De Vargas et al 2007;Sato and Chiyonobu 2009). The distribution patterns of nannoplankton are strongly related to surface water temperature and nutrients (Imai et al 2015;Kanungo et al 2017).…”