Most of the loess in the southeast of the Ebro Valley encompass mostly the Marine Isotope Stage 2 (MIS2) but some exceptions date back to more than 115 ka. Soils formed on these older loess deposits are normally categorised as red soils. We studied the pedogenesis of two of these red soils. Macro-micromorphological, particle size, color-redness rating, and iron form analyses were performed in combination with luminescence and radiocarbon dating. Mas de l’Alerany is a primary loess deposit, 3.15 m thick. Recarbonation is shown as carbonate coatings covering previous clay coatings in a red matrix, besides carbonate nodules and rhizocretions. Its deepest horizon dates back to ca. 140 ka. Chiprana is a 3.2 m loess-like sequence. It also reveal carbonate nodules and rhizocretions throughout the profile, together with a strong bioturbation and frequent queras, which are channel infillings of biosparite surrounded by decarbonated reddish hypocoatings. The bottom of the sequence has an age between 100 and 130 ka and shows residual clay coatings. The age of the upper part is about 30 ka, while the biosparite grains have an age of 26 ka. The genesis of the Mas de l'Alerany red soil, after its deposition, comprises the subsequent processes of decarbonation - rubefaction - clay illuviation - recarbonation. Chiprana presents a similar succession, but with a more recent decarbonation due to the biological activity that generated the queras, which were responsible for revealing the previously rubefacted material. Although Mas de l’Alerany and Chiprana red soils were probably formed from loess of the penultimate glaciation and both underwent a similar cycle of processes, the origin of the red colours in Chiprana is due to micro-site, biologically driven recent decarbonation. Our results suggest that the biological activity may play an important role in the reddening process in similar Mediterranean soils.

埃布罗河谷东南部的大多数黄土主要包括海洋同位素第二阶段（MIS2），但有些例外可追溯到115 ka以上。这些较早的黄土沉积物上形成的土壤通常被归类为红色土壤。我们研究了其中两种红色土壤的成岩作用。结合发光和放射性碳测年进行了宏观微观形貌，粒度，色红等级和铁形态分析。Mas de l'Alerany是主要的黄土矿床，厚度为3.15 m。再碳酸化显示为碳酸盐涂层，除了碳酸盐结节和根瘤根外，它覆盖了以前红色基质中的粘土涂层。它最深的地平线可以追溯到大约 140 ka。Chiprana是一个3.2 m的黄土样序列。它还在整个剖面中显示出碳酸盐结节和根瘤菌，加上强烈的生物扰动和频繁的丘疹，这是生物碳酸钙的通道填充物，周围是脱碳的红色底涂层。序列的底部年龄在100到130 ka之间，并显示出残留的粘土涂层。上部的年龄大约为30 ka，而生物滑石颗粒的年龄为26 ka。Mas de l'Alerany红壤的沉积后，其形成过程包括脱碳-磨碎-粘土浸润-再碳化的后续过程。Chiprana表现出相似的连续性，但由于产生斑马的生物活性而出现了较近的脱碳作用，该斑马负责揭示先前的仿生材料。尽管Mas de l'Alerany和Chiprana红色土壤可能是由倒数第二次冰川形成的黄土形成的，并且都经历了相似的过程循环，但Chiprana中红色的起源是由于微场所的，生物驱动的近期脱碳作用所致。我们的结果表明，在类似的地中海土壤中，生物活性可能在变红过程中发挥重要作用。