In arid and semi-arid climates, soil development is strongly influenced by seasonal patterns and biogenic activity, and often results in pervasive pedogenic horizons consisting of highly concentrated carbonate. In Brazil, such horizons enriched in calcium carbonate are common and relatively well-studied in paleosols of the Upper Cretaceous Marília Formation. However, detailed analyses on the sequence of mineral precipitation phases and the role of organisms in these processes are still lacking. The present work describes eight argillic and calcic horizons characterized by different degrees of carbonate accumulation. Argillic horizons show translocation clay structures and weak to moderate cementation by calcium carbonate. Calcic horizons contain moderate to high carbonate accumulations ranging from powdery coatings to nodular masses of micrite. Carbonate distribution in these horizons is preserved largely as carbonate-cemented macropores produced by such ichnofossils as Planolites, Taenidium, Naktodemasis, Skolithos, Palaeophycus and calcareous rhizocretions. Moreover, stable isotope data, respired soil CO₂ function, and cathodeluminescence (CL) of the paleosol samples were used to evaluate soil paleovegetation, paleoproductivity, and the distinctive stages of calcite precipitation. Stable isotopic analysis suggests that paleovegetation cover in the paleosols was predominantly C₃-photosynthsizing plants. The relationship between bioturbation indices and soil respiration suggests a positive pattern of paleoproductivity controlled by higher moisture conditions and the increased activity of soil fauna. Finally, CL imaging shows that there were multiple stages of carbonate precipitation with both α-type and β-type fabrics that are interpreted as abiotic and biotic processes during pedogenesis.

在干旱和半干旱气候下，土壤发育受到季节模式和生物成因活动的强烈影响，并常常导致由高浓度碳酸盐组成的普遍成土层。在巴西，这种富含碳酸钙的地层很普遍，并且在上白垩统玛丽亚组的古土壤中被研究得比较透彻。但是，仍然缺乏对矿物沉淀阶段顺序和生物在这些过程中的作用的详细分析。目前的工作描述了以碳酸盐堆积程度不同为特征的八个泥质和钙质层位。土质层位表明粘土结构易位，碳酸钙使胶结作用弱化至中度。钙质层位含中等至较高的碳酸盐堆积，范围从粉状涂层到球状微晶状块。攀缘石，Ta烯，核生孢子，Skolithos，古生物和钙质根瘤菌。此外，使用稳定的同位素数据，土壤呼吸的CO ₂功能和古土壤样品的阴极发光（CL）来评估土壤古植被，古生产力和方解石沉淀的独特阶段。稳定的同位素分析表明，古土壤中的古植被覆盖主要是C _3。-光合植物。生物扰动指数与土壤呼吸之间的关系表明，较高的水分条件和土壤动物活动的增加控制了古生产力的正向变化。最后，CL成像显示，α型和β型织物存在碳酸盐沉淀的多个阶段，这被解释为成岩过程中的非生物和生物过程。