Abstract
Nojiri-ko Formation is the sight of many vertebrate fossils, including those of Naumann’s elephants (Palaeoloxodon naumanni). In total, 15,989 materials have been obtained from the first excavation at Lake Nojiri in 1962 until the 22nd excavation in 2018. In this study, we aimed to understand the variations in the number of fossils by stratigraphic level and the changes in the fossil density per unit time. Fossils from the T4-T6 unit (43.8-42.6 ka) of the Tategahana Sand Member of the Nojiri-ko Formation showed the highest number of fossils per unit of time. Further, the Minimum Number (69) of individuals was estimated from the Naumann’s elephant molar fossils from the Nojiri-ko Formation. Based on the characteristics of the age profile of the Naumann’s elephant fossils, the age composition of T4-T6 and T7 units differed from that of other strata, indicating that the Naumann’s elephants in this stratum may have died collectively due to selective mortality. Various problems exist in typing the age structures, and thus, considering and studying different associated factors is necessary for future studies.
