Multi-millennia surface dynamics: Novel investigation approach unveils climate relation to mountain erosion (Serra da Estrela, Portugal)

IF 3.1 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL Geomorphology Pub Date : 2024-09-04 DOI:10.1016/j.geomorph.2024.109416
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Abstract

Multi-millennia data logs on surface denudation variation in alpine landscapes are scarce, yet they are needed to understand the impacts of environmental changes on denudation. On the example of the Serra da Estrela plateau in Portugal, we explored a new archive, vertical bedrock outcrops (tors), and the capability of the Tor Exhumation/Exposure Approach (TEA) to capture surface denudation variations even in formerly glaciated landscapes. Therefore, we used vertical in-situ 10Be to date surface exposure of tor slopes in formerly glaciated and non-glaciated parts of the plateau during the last glacial period.

Based on the surface exposure ages, surface denudation variations covering the last ∼200 ka could be derived that revealed glacial retreat dynamics in greater detail. Higher isotope contents and, thus, surface exposure ages were found in the non-glaciated area. At the formerly glaciated sites, the ice margin retreat is reflected in the isotope signature of the tors. The younger rock surfaces had a higher chemical weathering degree than older surfaces at the non-glaciated site as a result of a higher water availability. Highest-elevation tors have experienced (subglacial/hydrothermal) chemical weathering, mass wasting and stripping (∼6 ± 0.5 ka) during the transition from a cool moist, to an oceanic-Mediterranean climate.

Yet, tors in the non-glaciated area yielded lower surface denudation rates with a maximum of 0.53 [mm yr−1] compared to the glaciated area (reaching values of up to 18.29 [mm yr−1]). Since the LGM and the concomitant increase in air temperature, surface denudation also distinctly changed. Temperature trends and surface denudation developed analogously for the last ∼150 ka. Vegetation change or human activity's impact on surface denudation cannot be discerned due to the too low chronological resolution. Overall, we demonstrated that multi-millennia tor records of variation in surface denudation can be obtained using the TEA, even in formerly glaciated areas. Thus, this study contributes to revealing the sensitivity of mountain erosion rates to past environmental changes.

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多千年地表动态:新颖的调查方法揭示了气候与山脉侵蚀的关系(葡萄牙埃斯特雷拉山脉)
有关高山地貌地表剥蚀变化的千年数据记录非常稀少,但要了解环境变化对剥蚀的影响却需要这些数据记录。以葡萄牙埃斯特雷拉山高原(Serra da Estrela)为例,我们探索了一种新的档案--垂直基岩露头(tors),以及 Tor Exhumation/Exposure Approach(TEA)捕捉地表剥蚀变化的能力,即使在以前的冰川地貌中也是如此。因此,我们利用垂直原位 10Be 测定了末次冰川时期高原上前冰川地区和非冰川地区托尔斜坡的地表裸露年代。根据地表裸露年代,可以得出过去 ∼200 ka 的地表剥蚀变化,从而更详细地揭示了冰川退缩的动态。非冰川地区的同位素含量较高,因此地表暴露年龄也较高。在以前冰川侵蚀的地方,冰缘后退反映在山体的同位素特征上。较年轻的岩石表面的化学风化程度高于未冰川化地区较古老的岩石表面,这是因为水的供应量较高。在从凉爽潮湿气候向海洋-地中海气候过渡的过程中,海拔最高的山丘经历了(亚冰川/热液)化学风化、大规模流失和剥蚀(∼6 ± 0.5 ka)。然而,与冰川地区相比,非冰川地区的山丘表面剥蚀率较低(最大值为 0.53 [mm yr-1],最高值为 18.29 [mm yr-1])。自全新世以来,随着气温的升高,地表剥蚀也发生了明显的变化。在过去的 ∼150 ka期间,温度变化趋势与地表剥蚀的发展情况类似。由于年代分辨率太低,无法辨别植被变化或人类活动对地表剥蚀的影响。总之,我们证明了利用 TEA 可以获得地表剥蚀的千年变化记录,即使在以前的冰川地区也是如此。因此,这项研究有助于揭示山区侵蚀率对过去环境变化的敏感性。
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来源期刊
Geomorphology
Geomorphology 地学-地球科学综合
CiteScore
8.00
自引率
10.30%
发文量
309
审稿时长
3.4 months
期刊介绍: Our journal''s scope includes geomorphic themes of: tectonics and regional structure; glacial processes and landforms; fluvial sequences, Quaternary environmental change and dating; fluvial processes and landforms; mass movement, slopes and periglacial processes; hillslopes and soil erosion; weathering, karst and soils; aeolian processes and landforms, coastal dunes and arid environments; coastal and marine processes, estuaries and lakes; modelling, theoretical and quantitative geomorphology; DEM, GIS and remote sensing methods and applications; hazards, applied and planetary geomorphology; and volcanics.
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