靜岡県島田・掛川市付近の第三系とその浮遊性有孔虫化石群

• Main Author: 斎藤 常正
• Format: Report
• Language: Japanese
• Published: 東北大學 1960
• Subjects: Planktonic foraminifera
• Online Access: http://hdl.handle.net/10097/33141; https://tohoku.repo.nii.ac.jp/?action=repository_uri&item_id=13014; https://tohoku.repo.nii.ac.jp/?action=repository_action_common_download&item_id=13014&item_no=1&attribute_id=18&file_no=1

Since the stratigraphy of the Kakegawa District, Shizuoka Prefecture was first undertaken by Nakajima (1886) in his geological map "Shizuoka", many authors have contributed to the geology and paleontology of the region. Among them, Makiyama in particular has contributed to the geology, sedimentology and paleontology of the Kakegawa District. In this region, Makiyama distinguished two horizons of Lepidocyclina, one in the early and the other in the middle Miocene, the latter representing the presumed youngest horizon within the Tertiary deposits of Japan. He also recognized that the diastrophism during the Miocene in this region exceeds that found in other regions of Japan. To determine the precise horizons of the Lepidocyclina and their respective geological ages, the writer made a micropaleontological and stratigraphical study of the Kakegawa District. The present study also aims to find whether the diastrophic movements in the Kakegawa District can be correlated with similar movements in other parts of Japan. The statigraphical subdivisions of the Teritary deposits in the Kakegawa District and their biostratigraphical characteristics are shown in Plate 3, and briefly outlined below. The Mikura and Setogawa groups, mainly of an alternation of hard, medium to fine grained sandstone and siltstone reveal a complex isoclinal structure, but as a whole with NE-SW trend. Being intensely disturbed by folding and faulting the detail stratigraphical sequence of those two groups is difficult, and since fossils are very rare and not well preserved when found, determination of the geological age of those groups remains uncertain. The Ooigawa group, which comprises the Seto (lower) and Horai (upper) formations was previously considered to be early Miocene in age. The Seto, mainly of massive hard black siltstone is in fault contact with the older Setogawa group and unconformably overlain with the Horai formation. The Horai comprises conglomerate, sandstone and an alternation of sandstone and siltstone. It lies unconformably ...