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Soil development on sediments and evaporites of the Messinian crisis
Catena ( IF 6.2 ) Pub Date : 2019-12-04 , DOI: 10.1016/j.catena.2019.104368
Markus Egli , Michael Plötze , Dmitry Tikhomirov , Tatjana Kraut , Guido L.B. Wiesenberg , Gabriele Lauria , Salvatore Raimondi

Vast areas in the Mediterranean are characterised by evaporite deposits of the Messinian crises (c. 6–5.3 Ma BP). During this period, large deposits were built up in shallow lagoon-like systems and are now found in southern Italy, Albania, Cyprus and Turkey. So far, soil formation on evaporites has been studied predominantly in subarid to arid environments. Although the formation of soils has received new significance, little is known about the evolutional trajectories on evaporites of the Mediterranean. We therefore studied soil formation in the Caltanissetta basin (Sicily) where evaporites are most widespread. The lithologies included the sequence: marine clay deposits, laminated marl (diatomite; Tripoli sediments), Calcare di Base (limestone), detritic deposits, gypsum (selenite). The chemical signature (immobile elements, rare earth elements) indicated that they all have a similar origin. Surprisingly, both an increasing Corg and carbonate content in the soils caused a decrease in the δ13C signal in carbonates and in part in the bulk soil. The low δ13C and δ18O values of carbonates in the parent material indicate a high rock-water (or meteoric water) interaction that has occurred during sedimentation and diagenesis. Organic matter was oxidised into the shallow lagoon-like systems and its carbon incorporated in the limestone.

Elemental leaching from silicates during pedogenesis was most intense in the soils that developed on clays and Tripoli sediments. Vertisols and Mollisols have evolved, together with a high amount of oxyhydroxides (non-crystalline and crystalline forms) and kaolinite. Only weak soil formation was recognisable at sites having gypsiferous parent material. The presence of a high amount of selenite hindered a more advanced evolution. The soils developed on detritic and gypsiferous material exhibited some palygorskite that was inherited from the parent material. At sites having selenite or limestone, shallow Aridisols or Mollisols are found. Weathering is weakly pronounced, e.g. indicated by a high proportion of trioctahedral minerals. Besides inheritance from the parent material, smectite and kaolinite are also actively formed in the soils with increasing weathering. Plagioclase and mica are the main sources of smectite and K-feldspar is a main source of kaolinite neo-formation.

The evaporite deposits vary greatly within short distances causing a high spatial diversity of soils. Consequently, soil quality strongly varies, which challenges agricultural use. Well-developed soil profiles and advanced weathering stages are only possible when marine clays, Tripoli sediments or detritic deposits are the parent material. Limestone (Calcare di Base) and gypsiferous sediments (selenite) strongly limit soil formation and mineral transformation.



中文翻译:

墨西尼危机的沉积物和蒸发物上的土壤发育

地中海广大地区的特征是发生了麦西尼危机的蒸发岩沉积(约6–5.3 Ma BP)。在此期间,大型沉积物堆积在浅泻湖状系统中,现在在意大利南部,阿尔巴尼亚,塞浦路斯和土耳其发现。到目前为止,主要是在干旱环境下研究蒸发物上的土壤形成。尽管土壤的形成已经有了新的意义,但对地中海蒸发岩的演化轨迹知之甚少。因此,我们研究了蒸发最普遍的卡尔塔尼塞塔盆地(西西里岛)的土壤形成。岩性包括以下顺序:海相粘土矿床,层状泥灰岩(硅藻土;的黎波里沉积物),Calcare di Base(石灰石),碎屑矿床,石膏(硒矿)。化学特征(固定元素,稀土元素)表明它们都有相似的起源。令人惊讶的是,两者的C都在增加土壤中的org和碳酸盐含量导致土壤中的有机物减少。δ碳酸盐中和部分散装土壤中的13 C信号。低δ13 C和δ母体材料中碳酸盐的18 O值表明在沉积和成岩过程中发生了高的岩石-水(或陨石水)相互作用。有机物被氧化成浅泻湖状系统,其碳被掺入石灰石中。

在成土过程中,硅酸盐中元素的浸出在粘土和的黎波里沉积物上发育的土壤中最为强烈。垂直溶胶和毛溶胶以及大量的羟基氧化物(非晶体和晶体形式)和高岭石已经形成。在具有石膏形母质的部位只能识别出较弱的土壤形成。大量亚硒酸盐的存在阻碍了更高级的发展。在有害的和石膏形的材料上发育的土壤表现出一些坡缕石,而坡缕石是从母体材料继承而来的。在含有亚硒酸盐或石灰石的地方,发现有浅的阿里地溶胶或莫利溶胶。风化作用较弱,例如,八面体矿物的比例很高。除了从父材料继承外,随着气候的增加,绿土和高岭石也活跃地形成在土壤中。斜长石和云母是蒙脱石的主要来源,钾长石是高岭石新形成的主要来源。

蒸发岩的沉积物在短距离内变化很大,导致土壤的高度空间多样性。因此,土壤质量变化很大,这给农业使用带来了挑战。仅当以海洋粘土,的黎波里沉积物或有害沉积物为母质时,才能发育出良好的土壤剖面和高级的风化作用。石灰石(Calcare di Base)和石膏状沉积物(亚硒酸盐)强烈限制了土壤的形成和矿物的转化。

更新日期:2019-12-04
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