Fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model
Fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model
复制标题
使用冰川地质反演模型重建芬诺斯坎迪亚古冰川学
作者：
J. Kleman;C. Hättestrand;Ingmar Borgström;A. Stroeven
摘要利用冰川地质反演模型重建了芬诺斯堪的纳维亚地区末次冰期以来的冰盖形态和流动模式的演变，该模型是一个理论模型，它形式化了利用地貌记录重建冰盖的过程。该模型使用映射的流动痕迹和冰川融水地貌，以及来自横切条纹和直到线理的相对年表，作为输入数据。流迹系统分为四种类型：（i）时间-海侵湿床冰消扇，（ii）时间-海侵冻床冰消扇，（iii）浪涌扇，（iv）同步非冰消（事件）扇。利用相对年表和聚集成冰川学上合理的模式，一系列的冰盖在不同的时间切片竖立。通过与年代地层记录和反映全球冰量的代用数据的对比，建立了一个年代学。地质证据存在几个离散的冰盖配置集中在斯堪的纳维亚山脉在早期Weichselian。建立的主要Weichselian Fennoscandian冰盖开始在大约70 Ka，我们的研究结果表明，它的特点是冰盖的质量中心位于挪威南部。这种配置有一个流动模式，这是很难再现目前的数值模型的芬诺斯堪的纳维亚冰盖。在末次盛冰期，主要的冰分水岭位于波的尼亚湾。冰分水岭的一个主要弯曲是由冰在斯堪的纳维亚山脉最低处向西北流出造成的。广泛的地区保存前晚Weichselian景观表明，冰盖有一个冻床核心区，这是只有部分减少的大小向内海侵湿床区在衰变阶段。
Abstract The evolution of ice-sheet configuration and flow pattern in Fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model, i.e. a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets. The model uses mapped flow traces and deglacial melt-water landforms, as well as relative chronologies derived from cross-cutting striae and till lineations, as input data. Flow-trace systems were classified into four types: (i) time-transgressive wet-bed deglacial fans, (ii) time-transgressive frozen-bed deglacial fans, (iii) surge fans, and (iv) synchronous non-deglacial (event) fans. Using relative chronologies and aggregation of fans into glaciologically plausible patterns, a series of ice-sheet Configurations at different time slices was erected. A chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume. Geological evidence exists for several discrete ice-sheet configurations centred over the Scandinavian mountain range during the early Weichselian. The build-up of the main Weichselian Fennoscandian ice sheet started at approximately 70 Ka, and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern Norway. This configuration had a flow pattern which is poorly reproduced by current numerical models of the Fennoscandian ice sheet. At the Last Glacial Maximum the main ice divide was located overthe Gulf of Bothnia. A major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the Scandinavian mountain chain. Widespread areas of preserved pre-late-Weichselian landscapes indicate that the ice sheet had a frozen-bed core area, which was only partly diminished in size by inward-transgressive wet-bed zones during the decay phase.