Some Remarks on Mammalian Faunas in the Early Pleistocene

Abstract

For the Osaka group and its allies, fossiliferous deposits of Plio-Pleistocene which are widely distributed in Kinki district, five zones are discriminated biostratigraphicaly basing upon mammalian fossils. These are as follows ascendingly:
1. Stegodon cf. elephantoides Zone >3.0m. y.
2. Stegodon insignis sugiyamai Zone ca. 2.5m. y.
3. Stegodon shodoensis akashiensis Zone ca. 2.0-1.5m. y.
4. Elephas shigensis Zone ca. 1.5-0.6m. y.
5. Stegodon orientalis Zone ca. 0.6-0.3m. y.
The age determination is estimated to take DRM, fission-track method and K-A chronology into consideration. Besides them, with due regard to the results of palynological investigation and floral change, they should be correlated with Villafranchian division of Perrier hill, Auvergne in southern France by Azzaroli (1967), such as Zone 1 to Lower-, Zone 2 to Middle-, Zone 3 & 4 to Upper Villafranchian and Zone 5 to post Villafranchian with each other. Remarkable faunal gaps exist between Zone 1 and Zone 2 and also between Zone 4 and Zone 5. Faunal turnover from Zone 1 to Zone 4 is characteristic and its procedure advanced from warm forest fauna of Indo-Malayan Faunal Complex to temperate and/or cool forest-steppe fauna of Sino-Siberian Faunal Complex. At the time of Zone 5, warm forest fauna revived again as Sino-Malayan Faunal Complex.
In the process to analyse those faunas in turn, it is also stated as to the Pliocene-Pleistocene boundary that the concept of Haug's Line is invalid from paleobiogeographical and paleoecological view point, because the faunal complex, like as Sino-Siberian, Indo-Malayan, Villafranchian (European), Blancan (North American) and African, was already established in Pliocene time and went on with their own faunal turnover independently. Therefore, in order to notice the pattern of faunal gap and turnover, it is important not only to treat some selected taxa but also faunal complex as a whole. Those complex had been disassembled from time to time in relation to intra-complex change, like as change of population density or population pressure brought about by habitat change, i. e. from forest to steppe or from steppe to desert. As a result of such diversity in complex, many faunal facies or sub-facies had been formed and localized. When the blend of those facies occured, resulted mix facies reacted to mother complex to reveal the faunal gap and faunal turnover.
In such a way, Pliocene-Pleistocene gap, Villafranchian turnover and Villafranchian-post Villafranchian gap may be explained.