Diatom Biostratigraphy and Geologic Age of the Maruyama and Kurasi Formations, Southern Sakhalin, and Their Correlation to the Neogene of the Tenpoku Area, Hokkaido
Diatom Biostratigraphy and Geologic Age of the Maruyama and Kurasi Formations, Southern Sakhalin, and Their Correlation to the Neogene of the Tenpoku Area, Hokkaido
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萨哈林岛南部丸山组和库拉西组的硅藻生物地层和地质时代及其与北海道天北地区新近纪的关系
DOI：
10.5026/jgeography.109.2_203
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发表时间：
2000
影响因子：
3.1
通讯作者：
K. Amano
中科院分区：
文献类型：
--
作者：
F. Akiba;C. Hiramatsu;I. Tsoy;K. Ogasawara;K. Amano
对库页岛南部Makarov和Dolinsk地区Maruyama组的硅藻生物地层学研究表明，其地质时间跨度约为14 Ma至3.5 Ma或更年轻，远远长于先前的估计(例如Inle，1992年的9.5-5.3 Ma)。在硅藻的基础上，给出了马卡洛夫地区库拉西组的中中新世时代。在马卡洛夫地区发现的秋叶(1986)、柳泽和秋叶(1998)硅藻带包括库拉西组库拉西组和丸山组下部第一段(NPD4Bb；中中新世中期，14.6/14.5-13.1 Ma)中的小叶暗藻亚带(NPD4Bb；12.9-11.5 Ma)和丸山组下部第一段(NPD5B；中新世上段，12.9-11.5 Ma)。在多林斯克地区丸山组的中部，观察到了大量重新加工的硅藻标本。这些组合所显示的最年轻的带是新上新世的Thalassiosira oestrupii亚带(NPD7Bb；下上新世，5.5-3.9/3.5 Ma)，因此多林斯克地区Maruyama组的中部应为上新世早期或更年轻。由于在北海道北部天保地区的玉池组中发现了类似的组合，至少部分为更新世，因此多林斯克地区丸山组中部的时代可能是更新世，这需要进一步的研究来验证。此外，我们对Yuzhno-Sakhalinsk以南Aniva地区的Sheshukova-Poretzkaya(1967)资料的重新评价表明，该地层还包含一个与鲁夏加利福尼亚岩带(NPD7A；上中新统，7.6-6.4 Ma)相关的区间。本研究在年代学上约束了研究剖面及其相关地层的古生物学、古地磁和古环境等地质资料。以丸山组为代表的相当长的地质年代学间隔表明该组内部存在地层空白，因此，对该组的进一步研究可能会阐明具有局部或全球意义的相对海平面变化的历史。
A diatom biostratigraphic study of the Maruyama Formation in the Makarov and Dolinsk areas of the southern part of Sakhalin Island indicates that its geologic time span ranges from ca. 14 Ma to 3.5 Ma or possibly younger, which is much longer than previous estimates (e.g. 9.5-5.3 Ma by Ingle, 1992). A middle Miocene age of the Kurasi Formation in the Makarov area is also given on the basis of diatoms. These results are presented with correlation to the Neogene sections in the Tenpoku area, northern Hokkaido.The diatom zones of Akiba (1986) and Yanagisawa and Akiba (1998) recognized in the Makarov area include the Denticulopsis simonsenii Subzone of the D. hyalina Zone (NPD4Bb; middle middle Miocene, 14.6/14.5-13.1 Ma) in the Kurasi Formation and the 1st Member of the lower part of the Maruyama Formation, and the D. praedimorpha Zone (NPD5B; upper middle Miocene, 12.9-11.5 Ma) in the 2nd Member of the lower part of the Maruyama Formation. In the middle part of the Maruyama Formation in the Dolinsk area, the type area for the formation, numerous specimens of reworked diatoms were observed. The youngest zone shown by those assemblages is the Thalassiosira oestrupii Subzone of the Neodenticula kamtschatica Zone (NPD7Bb; lower Pliocene, 5.5-3.9/3.5 Ma), thus the middle part of the Maruyama Formation in the Dolinsk area should be of early Pliocene or younger ages. As similar assemblages are known from the Yuchi Formation in the Tenpoku area of northern Hokkaido, which is of Pleistocene age at least in part, the middle part of the Maruyama Formation in the Dolinsk area may be Pleistocene in age, which should be tested by further studies. In addition, our re-evaluation of Sheshukova-Poretzkaya's (1967) data from the Aniva area, south of Yuzhno-Sakhalinsk, suggests that the formation also contains an interval correlative to the Rouxia californica Zone (NPD7A; upper upper Miocene, 7.6-6.4 Ma).The present study geochronologically constrains other geological data such as paleontology, paleomagnetism, and paleoenvironments from the studied sections and their correlative strata. The considerably long geochronologic interval represented by the Maruyama Formation suggests stratigraphic gaps within the formation, thus a further study of the formation may elucidate the history of relative sea-level changes which have localor global implications.