Post-Miocene cold-water molluscan faunas from Hokkaido, Northern Japan
Post-Miocene cold-water molluscan faunas from Hokkaido, Northern Japan
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日本北部北海道的后中新世冷水软体动物群
DOI：
10.1016/0031-0182(94)90242-9
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Morio Akamatsu
中科院分区：
文献类型：
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作者：
A. Suzuki;Morio Akamatsu
北海道上新世至近代软体动物群主要分为三个动物群，从最古老到最年轻：泷川本别，Setana和Oyashio动物群。它们对应于后中新世时期日本冷水动物群的基本划分。生物地层学和放射性测量资料表明，泷川-本别阶被归属于ca。6.0 - 2.0 Ma，Setana阶段至约。2.0 - 0.6 Ma，Oyashio阶段至0.6 Ma-现在。泷川-本别动物群的特征是Fortipecten takahashii，在冷温带至亚北极气候条件下繁荣。根据地层层位和物种组成，Setana动物群可分为上、下两类。低Setana动物群，包括Yabepecten tokunagai，存在于亚北极气候条件下。Setana阶段的开始尤其以嗜冷分类群为标志，例如Chlamys islandicus。这一冷却事件似乎是由于早更新世冰川作用的加强。上溯Setana动物群以Mizuhopecten tokyoensis（s.s.）生活在冷温带气候条件下。Oyashio动物群由现存的冷水物种组成，如受到Oyashio海流影响的Mizuhopecten yessoensis。然而，在中更新世（约2000年），一个以暖水元素为特征的软体动物群在北海道生活了很短的时间。0.4在温暖的间冰期。上述动物群的演替可能受冰川-海平面变化、气候变化、构造运动等环境变化的控制，可能发生在新生代晚期的西北太平洋。这些动物群在北海道的出现可能是来自北方地区的北方成分的迁入所致。
Pliocene to Recent molluscs from Hokkaido are divided mainly into three faunas, from oldest to youngest: the Takikawa-Honbetsu, the Setana and the Oyashio faunas. They correspond to the fundamental division of Japanese cold-water faunas in post-Miocene time. Biostratigraphic and radiometric data show that the Takikawa-Honbetsu stage is assigned to ca. 6.0−2.0 Ma, the Setana stage to ca. 2.0−0.6 Ma, and the Oyashio stage to 0.6 Ma-Present. The Takikawa-Honbetsu fauna, characterized byFortipecten takahashii, flourished under cool-temperate to subarctic climatic conditions. The Setana fauna can be subdivided into two, lower and upper, by stratigraphic horizon and species composition. The lower Setana fauna, includingYabepecten tokunagai, existed under subarctic climatic conditions. The onset of the Setana stage is marked in particular by cryophilic taxa such asChlamys islandicus. This cooling event appears to have resulted from an intensification of glaciation during the early Pleistocene. The upper Setana fauna is, in turn, characterized byMizuhopecten tokyoensis(s.s.) and lived under cool-temperate climatic conditions. The Oyashio fauna is composed of extant cold-water species such asMizuhopecten yessoensisthat have been affected by the Oyashio current. However, a molluscan fauna characterized by warm-water elements lived in Hokkaido for a short time in the middle Pleistocene (ca. 0.4 Ma), during a warm interglacial period. The faunal succession mentioned above is presumably controlled by environmental changes, such as glacio-eustacy, climatic changes, tectonic movements, etc., which may have occurred in the northwestern Pacific during the late Cenozoic time. The appearance of these faunas in Hokkaido probably resulted from the immigration of boreal elements from the northern regions.