Abstract

Paleosoil accretions of carbonates in the Tandilia system (Southern Pampas, Argentina) dated to the lower/middle Pleistocene age are locally referred to as tosca. The characterization of this indurated layer of carbonates were analyzed via a biophysicochemical approach, including, physicochemical analysis of soils, mineral x-ray diffraction of the tosca, and microbial diversity of modern soils and tosca layers. The minerals found within tosca were calcite, albite, muscovite, quartz, orthoclase and dolomite in order of most to least abundant. The microbial metataxonomics of tosca was described for the first time. The most abundant microorganisms in tosca were g_Geobacter, g_Pseudonocardia and p_Gemmatimonadetes2 and redundancy analysis of physicochemical parameters and relative microbial abundances revealed positive correlations between Nitrospirae and calcium ions, while mineral and microbial correlations associated Gemmatimonadetes and Firmicutes with calcite and dolomite presence. Magnetospirillum, Geobacter and Bacillus were present in the tosca and the soil above, indicating possible prenucleation sites for calcite and dolomite. Core microorganism abundance was >80% throughout horizons including tosca, hence either microbial entrapment via calcium carbonate precipitation or microbial leaching occurred within this layer.

摘要

Tandilia 系统（阿根廷南部潘帕斯）中碳酸盐的古土壤增生可追溯到下/中更新世，当地称为tosca。通过生物物理化学方法分析了这种硬化碳酸盐层的特征，包括土壤的物理化学分析、托斯卡的矿物 X 射线衍射以及现代土壤和托斯卡层的微生物多样性。在托斯卡内发现的矿物按丰度从高到低的顺序依次为方解石、钠长石、白云母、石英、正长石和白云石。首次描述了tosca的微生物元分类组学。tosca中含量最多的微生物是 g_ Geobacter , g_Pseudonocardia和 p_ Gemmatimonadetes2以及理化参数和相对微生物丰度的冗余分析揭示了 Nitrospirae 和钙离子之间的正相关，而矿物和微生物的相关性将 Gemmatimonadetes 和 Firmicutes 与方解石和白云石的存在相关联。磁螺，Geobacter菌和芽孢杆菌存在于托斯卡和上述土壤中，指示用于方解石和白云石可以预成核位点。包括tosca在内的整个层位的核心微生物丰度 > 80% ，因此在该层内发生了通过碳酸钙沉淀或微生物浸出的微生物截留。