北海道石狩平野・野幌丘陵からの前期-中期更新世哺乳動物化石群の発見

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From a gravel quarry at the Otoebetsugawa Basin, near the southern margin of the Nopporo Hills, a horn of Bison and its cranial bone were discovered by workers there in 1972 (AKAMATSU et al., 1973). Since then, many fossil bones and teeth of mammals have been yielded from the same locality and have been collected by the workers. In 1980, the authors had opportunity to contact with them, and carried out geological survey to that gravel quarry and surrounding areas as well as identification for those fossil bones and teeth. The results of those studies are summarized as follows. 1. Amount of fossil bones and teeth attain more than 1400 specimens though fragmental. Up to now, the following specimens are identified: a fragmental pieces of elephant tusk and five molars of Mammuthus (assigned to M. sp. cf. paramammonteus and M. sp. cf. armeniacus); cranial (occipial) bone and horn of Bison sp.; two specimens of Artiodactyla extremities; two mandibula, many fragmental pieces of vertebrate and costae of Cetacea (Mystacoceti); a mandibula of Odobenus sp.; mandibula, humerus, costae and cranial bone of sea cow (Hydrodamalis sp.); fossil bones of other mammals. 2. As to the stratigraphic levels of those fossil bones and teeth, two horizons are discriminated; the lower is in the basal sand and gravel of the Shimonopporo Formation, while the upper is lain in the basal gravel of the overlying Otoebetsugawa Formation. The Kitahiroshima fauna of the former consists of Mammuthus sp. cf. paramammonteus, Hydrodamalis sp., Odobenus sp., Mystacoceti, Artiodactyla etc., and the Otoebetsugawa fauna of the latter comprises Mammuthus sp. cf. armeniacus and Bison sp.. 3. Although the Kitahiroshima fauna is representative of such mixed assemblage of marine and continental as Cetacea, Sirenia, Pinnipedia, Proboscedea and Artiodactyla, they are assumed to be autochthonous from the evidence of well preservation of fossils. Furthermore, it is probable that the sedimentary environment is estuary condition affected by cold current near the land. 4. From the stratigraphical, biostratigraphical (molluscan and pollen analysis) and magneto-stratigraphical studies, the Shimonopporo Formation ranges from the latest Early Pleistocene or the earliest Middle Pleistocene, and the Otoebetsugawa Formation belongs to the Middle Pleistocene. 5. Fossil elephant hitherto known in Hokkaido are Palaeoloxodon naumanni and Mammuthus primigenius, which characterize Middle to Late Pleistocene mammalian faunas. Therefore, it is significant that the presence of the Early to Middle Pleistocene mammals are confirmed in Hokkaido. The present findings may contribute in consideration of paleogeography of Hokkaido and migration route of continental fauna to the Japanese islands.
地学団体研究会の論文
1983-05-25

北海道石狩平野・野幌丘陵からの前期-中期更新世哺乳動物化石群の発見

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