Wagner Thomas, Fritz Harald, Stüwe Kurt, Nestroy Othmar, Rodnight Helena, Hellstrom John, Benischke Ralf
Institute of Earth Sciences, University of Graz, Heinrichstraße 26, A-8010 Graz, Austria.
Geomorphology (Amst). 2011 Nov 1;134(1-2):62-78. doi: 10.1016/j.geomorph.2011.04.024.
The transition zone of the Eastern Alps to the Pannonian Basin provides one of the best sources of information on landscape evolution of the Eastern Alpine mountain range. The region was non-glaciated during the entire Pleistocene. Thus, direct influence of glacial carving as a landscape forming process can be excluded and relics of landforms are preserved that date back to at least the Late Neogene. In this study, we provide a correlation between various planation surfaces across the orogen-basin transition. In particular, we use stream terraces, planation surfaces and cave levels that cover a vertical spread of some 700 m. Our correlation is used to show that both sides of the transition zone uplifted together starting at least about 5 Ma ago. For our correlation we use recently published terrestrial cosmogenic nuclide (TCN) burial ages from cave sediments, new optically stimulated luminescence (OSL) ages of a stream terrace and U-Th ages from speleothems. Minimum age constraints of cave levels from burial ages of cave sediments covering the last ~ 4 Ma are used to place age constraints on surface features by parallelizing cave levels with planation surfaces. The OSL results for the top section of the type locality of the Helfbrunn terrace suggest an Early Würm development (80.5 ± 3.7 to 68.7 ± 4.0 ka). The terrace origin as a penultimate gravel deposit (in classical Alpine terminology Riss) is therefore questioned. U-series speleothem ages from caves nearby indicate formation during Marine Isotope Stages (MIS) 5c and 5a which are both interstadial warm periods. As OSL ages from the terrace also show a time of deposition during MIS 5a ending at the MIS 5/4 transition, this supports the idea of temperate climatic conditions at the time of deposition. In general, tectonic activity is interpreted to be the main driving force for the formation and evolution of these landforms, whilst climate change is suggested to be of minor importance. Obvious hiatuses in Miocene to Pleistocene sediments are related to ongoing erosion and re-excavation of an uplifting and rejuvenating landscape.
东阿尔卑斯山向潘诺尼亚盆地的过渡地带是了解东阿尔卑斯山脉景观演化的最佳信息源之一。该地区在整个更新世都未被冰川覆盖。因此，可以排除冰川侵蚀作为一种景观形成过程的直接影响，并且保存了至少可追溯到新近纪晚期的地貌遗迹。在本研究中，我们给出了造山带 - 盆地过渡带不同夷平面之间的对比关系。具体而言，我们利用了河流阶地、夷平面和洞穴层级，它们在垂直方向上的跨度约为700米。我们的对比关系用于表明，至少从约500万年前开始，过渡带两侧是一起隆升的。为了进行对比，我们使用了最近发表的洞穴沉积物的陆地宇宙成因核素（TCN）埋藏年龄、一条河流阶地的新光释光（OSL）年龄以及洞穴次生碳酸盐的铀 - 钍年龄。利用洞穴沉积物埋藏年龄对过去约400万年洞穴层级的最小年龄限制，通过将洞穴层级与夷平面平行对比，来确定地表特征的年龄限制。海尔布伦阶地典型地点顶部的OSL结果表明其形成于末次冰期早期（80.5 ± 3.7至68.7 ± 4.0千年）。因此，该阶地作为倒数第二次砾石沉积（按照经典的阿尔卑斯术语为里斯冰期）的起源受到质疑。附近洞穴的铀系洞穴次生碳酸盐年龄表明其形成于海洋同位素阶段（MIS）5c和5a，这两个阶段都是间冰期温暖期。由于阶地的OSL年龄也显示在MIS 5a期间有一个沉积时期，并在MIS 5/4过渡时结束，这支持了沉积时期气候温和的观点。总体而言，构造活动被认为是这些地貌形成和演化的主要驱动力，而气候变化的作用则被认为较小。中新世至更新世沉积物中明显的间断与正在隆升和复苏的景观的持续侵蚀和再挖掘有关。
