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首页> 外文期刊>Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen >High-resolution stratigraphy from the continental record of the Middle Miocene Northern Alpine Foreland Basin of Switzerland
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High-resolution stratigraphy from the continental record of the Middle Miocene Northern Alpine Foreland Basin of Switzerland

机译：来自瑞士中新世中部北部高山前陆盆地大陆记录的高分辨率地层

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We present a new chronology for the Middle Miocene continental record of the Northern Alpine Foreland Basin of Switzerland. The investigated sediments belong to the Upper Freshwater Molasse (OSM) and reach a maximum thickness of 900 m. The sediments consist mainly of alluvial fan and fluvial deposits, but lake and pond environments are occasionally also documented. The investigated sections contain highly fossiliferous horizons with very diverse and characteristc faunas. The integration of mammal-based biostratigraphy, magnetostratigraphy and radiometric age data allow an excellent high-resolution chronostratigraphic framework for the OSM deposits to be established. Approximately 40,000 mammal teeth from screenwash collections derived from more than 60 localities form the basis of our study. Thirteen characteristic local mammal assemblages within the OSM have been recognized, covering the European Neogene mammal (MN) units from MN 4 to the base of MN 9 (ca. 17.5-11 Ma). Since nearly all key-species of the European MN-reference localities are recorded in the research area, they enable a reliable correlation to the MN-scheme. The biozonation proposed here is constrained by magnetostratigraphic sections, radiometrically dated volcanic ash layers and other local and regional stratigraphic marker beds. The European reference localities of MN 4 to MN 7+8 are correlated into the local faunal succession presented here according to the MN-zonation proposed by MEIN (1975, 1989). As a result, the distribution of the reference localities within the chronologic time scale is very asymmetric. The reference localities Sansan (France, MN 6), Steinheim (Germany, MN 7), and Anwil (Switzerland, MN 8) probably occurred within only 0.5 Myr, whereas the reference localities Pontlevoy (France, MN 5) and Sansan are separated by approx. 1.4 Myr. Since nearly all key-species of the European MN-reference localities are recorded within our research area, we aim to establish precise time brackets and/or boundaries between the European MN-units valid for Central Europe. We also attempt a correlation to other well-established local mammal zonations in Spain and southern Germany. Both the Swiss and Spanish mammal zonations are well elaborated and magnetostratigraphically constrained. Our biostratigraphic data presented here agree well with those of Germany (Bavaria) and Austria from the eastern part of the Molasse basin. The numerical ages of the MN-zones, however, differ considerably by ca. 0.5-1.0 Myr from the Spanish records. Until now, differences in the timing of the MN-zones have been explained by strong differences in the local faunal succession (provincialism) and/or different interpretation of MN-zones. It is suggested, however, that major faunal events used for the MN-zonation (e.g. the first occurrence date, FOD, of modern cricetids) are highly diachronous from Central to Western Europe (Spanish bioprovince). The diachrony of the FOD of modern cricetids is probably caused by their east-west immigration, whereas the diachronous extinction of the eomyid genus Ligerimys appears to have been caused by a local environmental and climatic change toward a more open and less humid habitat.
机译：我们为瑞士北部高山前陆盆地的中新世中期记录提供了一种新的年代学。被调查的沉积物属于上层淡水莫拉斯（OSM），最大厚度为900 m。沉积物主要由冲积扇和河床沉积物组成，但偶尔也有湖泊和池塘环境的记录。被调查的部分包含高度化石的地层，具有非常多样和特征化的动物群。基于哺乳动物的生物地层学，磁地层学和辐射年龄数据的整合，为OSM矿床建立了极好的高分辨率年代地层学框架。来自60多个地方的筛洗收集物中约有40,000颗哺乳动物牙齿构成了我们研究的基础。 OSM内的13种特征性本地哺乳动物群已被发现，涵盖了从MN 4到MN 9底（约17.5-11 Ma）的欧洲新基因哺乳动物（MN）单元。由于欧洲MN参考地区的几乎所有关键物种都记录在研究区域中，因此它们使与MN模式的可靠关联成为可能。这里提出的生物分区受到地磁地层剖面，放射性测年火山灰层以及其他局部和区域地层标志层的限制。根据MEIN（1975，1989）提出的MN分区，将MN 4到MN 7 + 8的欧洲参考位置与此处介绍的当地动物区系相关。结果，按时间顺序排列的参考地点分布非常不对称。参考位置Sansan（法国，MN 6），Steinheim（德国，MN 7）和Anwil（瑞士，MN 8）可能只出现在0.5 Myr之内，而参考位置Pontlevoy（法国，MN 5）和Sansan被分隔大约1.4马币由于欧洲MN参考地区的几乎所有关键物种都记录在我们的研究区域内，因此我们旨在在适用于中欧的欧洲MN单位之间建立精确的时间段和/或界限。我们还尝试与西班牙和德国南部其他成熟的本地哺乳动物地带建立关联。瑞士和西班牙的哺乳动物区带都经过精心设计，并受到地磁地层学的限制。我们在此提供的生物地层学数据与莫拉塞盆地东部的德国（巴伐利亚）和奥地利的生物地层数据非常吻合。但是，MN区的数字年龄大约相差约20％。西班牙记录中的0.5-1.0马币。到目前为止，MN区域时间的差异已经通过当地动物区系演替（省主义）和/或MN区域的不同解释的强烈差异来解释。但是，建议用于MN区划的主要动物区系事件（例如，现代cr足类动物的首次发生日期FOD）与中欧和西欧（西班牙生物省）高度不同。现代cr骨鱼类的FOD历时可能是由它们的东西向移民引起的，而线粒体属Ligerimys的历时灭绝似乎是由于当地环境和气候变化导致了其向更开放，更潮湿的栖息地的转变。

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