Proposing a new conceptual model for the reconstruction of ice dynamics in the SW sector of the Scandinavian Ice Sheet (SIS) based on the reinterpretation of published data and new evidence from optically stimulated luminescence (OSL) dating

C. Lüthgens, Jacob Hardt, M. Böse
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引用次数: 22

Abstract

Abstract. We propose a new concept of the Weichselian ice dynamics in the south-western sector of the Baltic Sea depression. The review of existing geochronological data from Germany, Denmark and southernmost Sweden in combination with new optically stimulated luminescence (OSL) data from the German Oder Lobe area is the basis for a reassessment and an improvement of previous ice dynamic models. Factors like the pre-existing topography, glaciotectonic features and the occurrence of till beds and inter-till deposits of varying origin are also taken into consideration for our process-based reconstruction of the sedimentary environments close to the ice margin and hence the ice dynamics of the Scandinavian Ice Sheet (SIS). During the early MIS 3 (marine isotope stage), the late MIS 3 and MIS 2, the SIS advanced into present-day terrestrial areas around the south-western Baltic Sea Basin. The first ice advance during the warming phase in early MIS 3 is poorly documented as the Ellund–Warnow Advance in Germany but may be correlated with the numerically dated Ristinge Advance in Denmark and Sweden. The late MIS 3 advance in contrast is reliably documented. It shaped the landforms of the Brandenburg Advance and the maximum Weichselian ice extent in the Oder Lobe area in north-eastern Germany and occurred contemporaneously with the Klintholm Advance in southern Sweden and Denmark. The lack of a corresponding till in various cliff profiles along the Baltic Sea coastline between southern Schleswig-Holstein and the island of Rügen can be explained by the distinct lobate structure of this ice advance, which was strongly guided by the pre-existing low-lying topography. We propose the horst of Bornholm, Denmark, acting as an ice divide, with ice-dammed lakes existing on the lee side between two glacier lobes. This lobate structure had not been considered in previous conceptual models, which led to seemingly conflicting chronological and stratigraphical interpretations. Our introduction of the lobate structure for the first time resolves these contradictions and integrates the data in a coherent model. The dynamics of the MIS 2 readvance to the Last Glacial Maximum (LGM) extent were clearly different to the previous advance and were most likely characterized by a more uniformly advancing ice front with a less lobate structure which also overrode the horst of Bornholm and the island of Rügen. This advance reached the maximum Weichselian ice extent in some parts of the south-western SIS, but, in the Oder Lobe area, it is proven to have terminated at a lesser extent than the early MIS 3 advance, but it did shape the most prominent morphological landform record of the last glacial cycle. In order to advance the reconstruction of Weichselian ice dynamics in the future, we strongly suggest using both an MIS-based terminology and a process-based approach in the interpretation of geochronological data to live up to the dynamic nature of continental ice sheets.
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基于对已发表数据的重新解释和光学激发发光(OSL)测年的新证据,提出了斯堪的纳维亚冰盖(SIS)西南段冰动力学重建的新概念模型
摘要我们提出了一个关于波罗的海低气压西南段魏奇塞利冰动力学的新概念。对来自德国、丹麦和瑞典最南端的现有地质年代学数据的回顾,结合来自德国奥德叶地区的新光学激发发光(OSL)数据,是重新评估和改进以前冰动力模型的基础。我们基于过程重建靠近冰缘的沉积环境,从而重建斯堪的纳维亚冰盖(SIS)的冰动力学,还考虑了诸如预先存在的地形、冰川构造特征以及不同来源的耕床和间耕沉积物的发生等因素。在MIS 3(海洋同位素阶段)早期、MIS 3和MIS 2晚期,SIS向现今波罗的海盆地西南部附近的陆地区域推进。在MIS 3早期变暖阶段的第一次冰推进在德国被称为Ellund-Warnow推进,但可能与丹麦和瑞典的Ristinge推进有关。相比之下,MIS 3的后期进展是可靠的。它塑造了勃兰登堡推进和德国东北部奥得叶地区最大的魏奇塞利冰范围的地貌,并与瑞典南部和丹麦的克林瑟姆推进同时发生。在石勒苏益格-荷尔斯泰因南部和r根岛之间的波罗的海沿岸的各种悬崖剖面中,缺乏相应的坡地,这可以用这种冰推进的独特的叶状结构来解释,这种冰推进是由先前的低洼地形强烈引导的。我们建议丹麦的博恩霍尔姆岛作为一个冰分水岭,在两个冰川裂片之间的背风面存在冰坝湖泊。在以前的概念模型中没有考虑到这种叶状结构,这导致了似乎相互冲突的年代和地层解释。我们首次引入的叶状结构解决了这些矛盾,并将数据集成到一个连贯的模型中。末次冰期极大期(LGM)前的MIS 2预进动力学明显不同于之前的预进,其特征很可能是更均匀地推进冰锋,其叶状结构较少,也覆盖了Bornholm和r根岛的主体。这一推进在SIS西南部分地区达到了最大的魏氏冰范围,但在奥得叶地区,它被证明比MIS 3早期的推进终止的程度要小,但它确实形成了末次冰期最突出的形态地貌记录。为了进一步推进Weichselian冰动力学的重建,我们强烈建议在解释地质年代学数据时同时使用基于mis的术语和基于过程的方法,以符合大陆冰盖的动力学性质。
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