ABSTRACT The present marine Baltic Sea basin (BSB) occupies an eroded Proterozoic intra-cratonic basin on the Fennoscandian shield. Competing models propose a Neogene fluvial origin, with later modification by glacial erosion, or a much younger development, with overdeepening beneath the Fennoscandian Ice Sheet (FIS). We test these alternatives using a first order source to sink sediment budget for the catchment of the BSB. Best estimates derived from geomorphic and cosmogenic nuclide evidence suggest depths of erosion over the last 1 Ma of 20 m in basement and 40 m in sedimentary rocks that surround the BSB. As the BSB has been overdeepened below a regional base level provided by the shallow Darss Sill at the boundary with the Kattegat, erosion of the BSB may be interpreted as glacial in origin, without a fluvial component. The estimated total volume of source area erosion is 30,628 km3 of which 87% is derived from the present BSB. Sediment volumes in the sink area within the limits of maximum Pleistocene glaciation are estimated at a minimum of 37,629 km3, after correction for local erosion, porosity, and carbonate losses. Marine Isotope Stage 12 and younger sediments account for 87% of the total Pleistocene sediment volume in the sink in Poland. Although significant uncertainties remain, the sediment budget is consistent with erosion of the BSB entirely by the FIS, mainly when the ice sheet reached its maximum extent and thickness during the Middle and Late Pleistocene glaciations.

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更新世冰川侵蚀波罗的海盆地的起源

摘要 目前的海相波罗的海盆地 (BSB) 位于芬诺斯坎迪亚地盾上的一个被侵蚀的元古代克拉通内盆地。竞争模型提出了一个新近纪河流起源，后来被冰川侵蚀修改，或者一个更年轻的发展，在芬诺斯堪的纳冰盖 (FIS) 下过度加深。我们使用一阶源来测试这些替代方案，以吸收 BSB 集水区的沉积物预算。来自地貌和宇宙成因核素证据的最佳估计表明，过去 1 Ma 的侵蚀深度在基底中为 20 m，在 BSB 周围的沉积岩中为 40 m。由于 BSB 在与 Kattegat 边界的浅 Darss Sill 提供的区域基准面以下过深，BSB 的侵蚀可能被解释为冰川起源，没有河流成分。源区侵蚀总量估计为 30,628 平方公里，其中 87% 来自当前的 BSB。在对局部侵蚀、孔隙度和碳酸盐损失进行校正后，最大更新世冰川作用范围内汇区的沉积物体积估计至少为 37,629 平方公里。海洋同位素第 12 阶段和更年轻的沉积物占波兰汇中更新世沉积物总量的 87%。尽管仍然存在重大的不确定性，但沉积物收支与完全由 FIS 对 BSB 的侵蚀一致，主要是在中更新世和晚更新世冰川期间冰盖达到其最大范围和厚度时。在对局部侵蚀、孔隙度和碳酸盐损失进行校正后，最大更新世冰川作用范围内汇区的沉积物体积估计至少为 37,629 平方公里。海洋同位素第 12 阶段和更年轻的沉积物占波兰汇中更新世沉积物总量的 87%。尽管仍然存在重大的不确定性，但沉积物收支与完全由 FIS 对 BSB 的侵蚀一致，主要是在中更新世和晚更新世冰川期间冰盖达到其最大范围和厚度时。在对局部侵蚀、孔隙度和碳酸盐损失进行校正后，最大更新世冰川作用范围内汇区的沉积物体积估计至少为 37,629 平方公里。海洋同位素第 12 阶段和更年轻的沉积物占波兰汇中更新世沉积物总量的 87%。尽管仍然存在重大的不确定性，但沉积物收支与完全由 FIS 对 BSB 的侵蚀一致，主要是在中更新世和晚更新世冰川期间冰盖达到其最大范围和厚度时。