@article{oai:niigata-u.repo.nii.ac.jp:00003235,
 author = {栗田, 裕司 and 田近, 淳},
 issue = {11},
 journal = {地質学雑誌, 地質学雑誌},
 month = {Nov},
 note = {A diverse marine dinoflagellate cyst assemblage of an Early Eocene age was recovered from the Mukai-engaru Formation of the Yubetsu Group，　Tokoro　Belt，　eastern　Hokkaido，　Japan，　from which no　fossil　occurrence　was　previously recorded．　The　Early　Eocene　age　is　the　youngest known　age　of　the　group　and　provides　two geochronological constraints significant to the regional tectonic history. First, the age of the formation agrees well with the accretionary prism model proposed　for　the　Yubetsu　Group，　since　the age　was　determined in　the　probable　youngest　part of　the　whole　group　in　the　model. Second, the present age determination denotes that the eastward accretion-subduction to the Paleo-Kuril Arc or　the　Okhotsk　Block　was　still　active　in　the Early　Eocene. The　observed　geochronological range　of　the　Yubetsu　Group　is　well　paralleled　by that　of　the　Hidaka Supergroup in　the　Hidaka Belt to the west, which implies a temporal similarity between the two confronting convergent margins.},
 pages = {808--811},
 title = {北海道東部、常呂帯湧別層群向遠軽層の渦鞭毛藻化石年代(前期始新世)とその意義},
 volume = {104},
 year = {1998}
}