ABSTRACT: Neogene sedimentary deposits are present in the Miyazaki region, southern Kyushu, on the Pacific side of southwestern Japan. The upper part of the Miyazaki Group, exposed in the Tsuma–Takanabe region of northern Miyazaki, is divided into the Tsuma, Sadowara, and Takanabe formations, in ascending order, and contains a planktic foraminiferal and calcareous nannofossil record of Pliocene events of the mid-latitude northwestern Pacific. The geological age of these units is based on magneto- and biostratigraphy. Five calcareous nannofossil datum horizons are recognized: the last occurrence (LO) of Reticulofenestra pseudoumbilicus, the termination of acme zone II of Reticulofenestra minutula var. C, the LO of R. minutula var. B, calcareous nannofossil datum plane A, and the termination of acme zone I of R. minutula var. C. Six planktic foraminiferal bioevents are also recognized: a coiling direction change, from sinistral to dextral, in the genus Pulleniatina; the first occurrence (FO) of Globorotalia crassaformis; the LOs of Globorotalia margaritae, Sphaeroidinellopsis seminulina, and Dentoglobigerina altispira; and the FO of Neogloboquadrina asanoi. The presence of two calcareous nannofossil bioevents, Datum A and the termination of acme zone I of R. minitula var. C, suggests that the normal and reversed polarity intervals of the upper part of the Takanabe Formation correspond to Chron C2An.1n (latest Gauss Normal Epoch) and Chron C2r.2r (earliest Matuyama Reversed Epoch), respectively. Based on combined floral and faunal data and magnetostratigraphic chron boundaries from the ATNTS2004, the upper part of the Miyazaki Group is Middle to Late Pliocene in age.

Files