Tectonic versus climatic control on the evolution of a loess–paleosol sequence at Beremend, Hungary: an integrated approach based on paleoecological, clay mineralogical, and geochemical data
Tectonic versus climatic control on the evolution of a loess–paleosol sequence at Beremend, Hungary: an integrated approach based on paleoecological, clay mineralogical, and geochemical data
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DOI：
10.1016/j.quaint.2010.10.032
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发表时间：
2011-08
影响因子：
2.2
通讯作者：
A. Varga;G. Újvári;B. Raucsik
中科院分区：
文献类型：
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作者：
A. Varga;G. Újvári;B. Raucsik
两个主要因素，气候和构造作用，在控制黄土-古土壤演化的作用进行了评估，在本研究的基础上，多代理数据集，包括软体动物，散装和粘土矿物，地球化学数据。最近的一个趋势是使用化学指标，如化学蚀变指数（CIA）的古气候重建黄土-古土壤序列跨越几十万年，但没有任何构造解释。讨论了地球动力学因素对物理侵蚀、化学风化以及风化指标的可能影响。显然，沉积环境中物理侵蚀和化学风化的相对速率可能受到地球动力学因素的重大影响，而不仅仅是受气候的影响。构造隆起的加剧导致物理侵蚀的增强，导致新鲜矿物表面的供应增加，与风化剂反应的时间减少。从理论上讲，这一过程可能会导致化学风化作用在一个序列中减少，而没有任何真实的气候变化。在所研究的Beremend（匈牙利）黄土-古土壤序列中，观察到化学风化减少的趋势，这可以用全球气候恶化和沉积盆地及其周围的加速隆起来解释。从理论上讲，由于非线性放大后，反映风化记录中气候变化的干旱化和风力增加，灰尘沉降增加也可能有助于这一过程。研究结果指出，在追踪数十万年（或数百万年）时间尺度上的过去化学风化趋势时，也应考虑构造作用的影响。这是因为构造效应可能会施加在CIA信号和扭曲，这表明在重建古气候变化的基础上，只有这个代理从某些黄土序列与年轻的造山带的潜在偏见。
The role of two major factors, climate and tectonism, in controlling loess–paleosol evolution has been evaluated in the present study based on a multi-proxy dataset comprising mollusc, bulk and clay mineralogical, and geochemical data. A recent trend has been to use chemical indices such as the chemical index of alteration (CIA) for paleoclimate reconstructions in loess–paleosol sequences spanning several hundreds of thousands of years, but without any tectonic interpretation. Possible effects of geodynamic factors on physical erosion, chemical weathering and consequently weathering proxies are discussed. Clearly, the relative rates of physical erosion and chemical weathering in a sedimentary environment could be significantly influenced by geodynamic factors and governed not just by climate. Intensifying tectonic uplift gives rise to enhanced physical erosion, leading to increased supply of fresh mineral surfaces having less time to react with weathering agents. In theory, this process may point towards decreasing chemical weathering in a sequence without any real changes of climate. In the studied loess–paleosol sequence at Beremend (Hungary) a trend of decreasing chemical weathering has been observed, which can be explained by a global climate deterioration and accelerating uplift in and around the sedimentary basin. Increasing dust sedimentation could theoretically also contribute to this process as a result of increasing aridification and wind strength reflecting climate change in weathering records following a non-linear amplification. The findings refer to the fact that the impact of tectonism should also be taken into consideration in tracing past chemical weathering trends on timescales of hundreds of thousands (or millions) of years. This is because tectonic effects may impose on the CIA signal and distort it suggesting a potential bias in reconstructing paleoclimate change based only on this proxy from certain loess sequences associated with young orogenic belts.