Paleolimnologic and paleoceanographic history of the Sea of Japan - a reconstruction based on diatoms -

最新的古地磁资料表明，日本大陆原本是亚洲大陆的一部分，后来随着日本西南部的顺时针旋转和日本东北部的逆时针旋转而向东南方向断裂和扩张。因此，“日本海”最初是一个湖泊。本研究的目的是描述20个淡水湖或浅海沉积物中的硅藻植物群，为重建该海域的古湖泊和古海洋学历史提供信息。特别是利用扫描电子显微镜将Aulacosira和Actinocyclus两个种划分为“型”，并展示了它们的地理和地层分布。1.在20个沉积物样品中鉴定了Aulacosira属的25种不同“形式”（A-U和X）和Actinocyclus属的3种（A、B和C）。2. RC 12 -394：Aulacosira“形式”的三种不同组合通过其丰度来区分。3.大岛山口 ...更多信息 england，Abura，所谓的Futoro组：Aulacosira“形式”组合的特征是“形式”B占优势。3.佐渡群岛，关，Masaragawa组：Aulacosira“form”I最丰富。4.诺托半岛、能登中岛、山田泥岩段：观察到优势“型”B和罕见的放线环属A种（“型”C）。5.福井、Demura和Hikime、Itoo组：在该组中只发现了重结晶的Aulacosira Sp.（“形式”X）。6.隐岐群岛、野越、Yui组：在该组中观察到罕见的几种Aulacosira“型”（B、H等）和单一的Actinocyclus“forni”（C）。从这些结果中，推导出以下内容：1。关的植物群完全由淡水硅藻组成，这些硅藻是在海洋还是湖泊时沉积下来的。该植物群与“二鸟组”和山田组泥岩段的植物群有很大的不同，这种差异可能是由于湖水较冷造成的。2.“Futoro组”的硅藻植物群与山田11/2段的相似。后者最上层的海洋物种的混合物表明，这些地层可能因此占据了与第一次入侵海洋的暖流相同的时间框架。3. RC 12 -394中的三个Aulacosira“形式”组合在上述陆地暴露的淡水成因的白垩纪岩石中没有发现。少

Recent paleomagnetic data suggest that Japanese mainland was originally a part of the Asian continent, and subsequently broke off and spread southeastward with the clockwise rotation of southwest Japan and the counterclockwise rotation of northeast Japan. The "Sea of Japan" thus originated as a lake. The purposes of this study are to described the diatom floras in 20 sediments formed when the sea was a fresh-water lake or shallow sea, and to provide information to reconstruct the paleoliminologic and paleoceanographic history of the sea. In particular, I classified Aulacosira and Actinocyclus species into "forms" by scanning electron microscopy, and showed their geographical and stratigraphical distributions. 1. Twenty-five different "forms" (A-U and X) of the genus Aulacosira and three (A, B and C) of the genus Actinocyclus were identified in the twenty sediment samples. 2. RC12-394: Three different associations of Aulacosira "forms" were distinguished by their abundances. 3. Oshima P … More eninsula, Abura, so-called Futoro Formation: Aulacosira "forms" association was characterized by the predominance of "form" B. 3. Sado Islands, Seki, Masaragawa Formation: Aulacosira "form" I was most abundant. 4. Noto Peninsula, Notonakajima, Yamatoda Mudstone Member: Dominant "form" B and rare Actinocyclus sp. A ("form" C) were observed in the member. 5. Fukui, Demura and Hikime, Itoo Formation: Only recrystallized Aulacosira Sp. ("form" X) was found in the formation. 6. Oki Islands, Nogoe, Yui Formation: scarce occurrence of several Aulacosira "form" (B, H and others) and single Actinocyclus "forni" (C) were observed in the formation. From these results, the following are deduced; 1. The Seki flora consists of exclusively fresh-water diatoms deposited when the sea was a lake. The flora is very different from that observed in "Futoro Formation" and Yamatoda Mudstone Member, and the difference could be caused by colder water of the lake. 2. The diatom flora in "Futoro Formation" has some resemblance to that of Yamatoda 11/2,ludstone Member. Admixture of marine species in the uppermost layer of the latter suggests that these strata may hence occupy the same time frame as the first invasion of warm current to the sea. 3. Three associations of Aulacosira "forms" in RC12-394 are not found in the aforementioned land-exposed fresh-water origin diatomaceous rocks. Less