@article{oai:mue.repo.nii.ac.jp:00001446,
 author = {川村, 寿郎 and 小山, 康宏 and 引地, 朗 and 推野, 康子 and 佐々木, 一成 and 今野, 亨 and 高野, 洋平},
 journal = {宮城教育大学紀要, BULLETIN OF MIYAGI UNIVERSITY OF EDUCATION},
 month = {Jan},
 note = {南部北上帯日頃市地区のシルル系層序は、これまで、日本の初期地史を研究する上で重要な研究対象とみなされてきた。我々は、日頃市地区のシルル系川内層の分布する10ルートセクションを詳細に調査し、大量の石灰岩微相の観察を基にして、岩相層序を再検討した。その結果、川内層は下位より基底部層、下部層、上部層に区分され、上部層はさらに石灰岩泥岩互層卓越部と石灰岩角礫岩卓越部とからなる。下部層の炭酸塩岩相は、島弧基盤の沈降後の炭酸塩台上にできたラグーン相を主とする。下部層の中の上部は、サンゴ類、層孔虫類、紅藻類から構築され、多量の石灰微生物類で連結された小規模な礁マウンドを含んでいる。下部層の中の最上部から上部層の中の下部は、亀裂、赤色～黄色の染色、紫色シルトの充填で特徴づけられ、その多くが炭酸塩台の離水を示唆する。それに対して、上部層は、主に炭酸塩台の縁辺から前面域で形成され、そこで頻発した炭酸塩混濁流堆積物が石灰岩泥岩互層卓越部となり、台縁～斜面での崩壊や土石流堆積物が石灰岩角礫岩卓越部となったと考えられる。川内層の岩相層序に類似した炭酸塩の累重は、同じ南部北上帯内の縁辺域でのシルル系セクションには不連続的であるが、西南日本の黒瀬川帯の祇園山地区や横倉山地区のシルル系石灰岩で認識されている。この広域的な類似性は、南部北上帯と黒瀬川帯が、堆積およびテクトニクスのセッティングとして連続した島弧陸棚で堆積したこととともに、シルル紀中期～後期当時の氾世界的な海水準変動に呼応したことをも意味している。, Silurian stratigraphy of the Hikoroichi area, the South Kitakami Terrane, has been traditionally regarded as the most significant research subject to study the earliest geohistory of Japan. We have investigated ten route sections of the Silurian Kawauchi Formation in detail and re-examined lithostratigraphy based on numerous observations of limestone microfacies. Consequently, the formation is subdivided into the basal, lower, and upper members, the last of which is composed of the limestone and mudstone alternation-dominated part and the limestone breccia-dominated part. Main carbonates of the lower member represent deposits of lagoon facies on the carbonate platform after the subsidence of the arc-island basement. The upper part of the lower member contains small reef-mounds which were constructed by corals, stromatoporoids and red algae and bound by abundant calcimicrobes. The Carbonates from uppermost part of the lower member to lower part of the upper member are characterized by cracking, red to yellow staining, or filling of purple siltstone, most of which suggest an emergency of the carbonate platform. In contrast, the upper member was mainly formed in the marginal to frontal areas of the carbonate platform; limestone and mudstone alternation-dominated part may have been the muddy deposits with frequent carbonate turbidites, and limestone breccia-dominated part is considered as collapsing or debris flow deposits in the platform edge to slope. Similar carbonate successions of the Kawauchi lithostratigraphy are discontinuous to the Silurian section within the marginal areas of South Kitakami Terrane, but are recognized to the Silurian limestone sections in Gion-yama and Yokokura-yama districts of the Kurosegawa Terrane in Southwest Japan. This regional similarity means the deposition on the continuous arc island-shelf as sedimentary and tectonic setting, and also the response to the global sea-level fluctuation in the Middle to Late Silurian times.},
 pages = {173--185},
 title = {南部北上帯日頃市地区のシルル系層序再訪},
 volume = {56},
 year = {2022}
}