陕西省丹凤县茶房村黄土-古土壤剖面风化程度及对气候变化的响应

对陕西丹凤县茶房村黄土剖面的地层学、沉积学特征以及常量元素、磁化率、粒度等进行了研究。结果表明:茶房村剖面具有表土(MS)→全新世黄土(L0)→古土壤(S0)→过渡黄土(Lt)→马兰黄土(L1)的地层序列;化学风化过程中元素Ca、Na、Mg、K和Si表现为迁移特征,Fe则相对富集,呈现NaSiMgKCaAlFe的迁移序列;剖面总体风化程度处于初等向中等过渡的阶段,不同地层的风化强弱顺序为S0LtL1L0。化学风化强度的变化表明该区自晚更新世以来气候经历了气候干冷→气候回暖→温暖湿润→气候转凉的变化过程。

Weathering Intensity of the Chafangcun Loess-paleosol Profile in Shaanxi,China and Its Response to Climate Change

The Chafangcun profile in Danfeng, Shaanxi, China were surveyed in detail and then sampled systematically. The stratigraphic and sediment logical characteristics, chemical weathering intensity and the profile structure were observed in the field. Magnetic susceptibility, particle-size distribution, geochemical characteristics were analyzed in laboratory. Results are shown as follows: (1)The stratigraphic sequences of Chafangcun profile changed with the stratigraphic series MS-L₀-S₀-L_t-L₁. (2) The major elements such as Ca, Na, Mg, K and Si were migrated and leached, while the element Fe was slightly enriched during the chemical weathering process. According to the migration ability, the major elements were ranked in the following order: Na>Si>Mg>K>Ca>Al>Fe. (3) The Chafangcun loess have finished the primary chemical weathering process and almost reached the secondary process as a whole. The aeolian sediments went through different degree of pedogenic modification in different periods with the sequence S₀>L_t>L₁>L₀. Geochemical characteristics of major elements indicate that the climate changed as "cool-dry (before 11500 a BP)→cool-wet(11 500~8 500 a BP)→warm-wet (8 500-3 100 a BP)→cool-dry (since 3100 a BP)".