The multiplicity of units present in a single loess bed greatly complicates the reconstruction of the history of polycyclic loess-derived soils. The present study implemented a combination of techniques to characterize different depositional events in a pedogenized loess formation of North-Western Italy. Field morphological observations, laboratory Particle Size Distribution (PSD) analyses, and single-grain image processing techniques were applied.

Five different loess depositions, or cycles, were distinguished in the field. Laser PSD curves highlighted the fine nature of the studied loess, which stood out even in comparison to similar Italian loess-derived soils. All PSD functions showed a tri/bimodal distribution with a dominant peak at 8–14 μm, wider in younger depositions. The second most relevant peak, at 0.5–4 μm, displayed a greater intensity in older cycles where it also fell in correspondence of slightly bigger particles. The fine-grained nature of the loess was read as a sign of its alluvial origin, therefore the Po plain has been addressed as the source of the material. This hypothesis was supported by evidence of a dominant SE-to-NW paleo-wind direction, proved by the spatial trends of the coarse and fine silt fractions. The typical aeolian size-dependant depositional trait of one of the cycles (IV) was however opposite to that of the other four loess depositions. Therefore, the source of this material was attributed to a site North of the study area where, right behind the Lanzo ultramafic massif, an ice lobe stretched during the Last Glacial Maximum (LGM). Image analysis supported this hypothesis: as the loess grains of cycle IV were significantly darker colored than the others, this would agree with the provenance from an ultramafic source. In conclusion, the variety of applied techniques allowed us to combine different pieces of information in order to assess the physical and morphological properties of the studied loess-derived soils, trying to determine the most probable sources of the material and the weathering pathways.

在一个单一的黄土层中存在大量的单元，这使得重建多环黄土来源的土壤的历史大大复杂化。本研究实施了多种技术组合，以表征意大利西北部成岩的黄土层中不同的沉积事件。应用了现场形态学观察，实验室粒度分布（PSD）分析和单颗粒图像处理技术。

在该领域中区分了五个不同的黄土沉积或循环。激光PSD曲线突出显示了所研究的黄土的优良性质，即使与类似的意大利黄土来源的土壤相比，该性质也很突出。所有的PSD功能都显示出三峰/双峰分布，其主峰在8–14μm处，在较年轻的沉积物中较宽。第二个最相关的峰为0.5–4μm，在较旧的循环中显示出更高的强度，在此过程中，它也随着稍大的颗粒而下降。黄土的细粒性质被认为是其冲积起源的标志，因此蒲平原已被视为该物质的来源。该假设得到了SE向NW主导的古风方向的证据的支持，粗粉和细粉尘组分的空间趋势证明了这一观点。然而，其中一个周期（Ⅳ）的典型的风成大小依赖于沉积特征与其他四个黄土沉积相反。因此，这种材料的来源归因于研究区域以北的一个位置，在该区域的正上方，Lanzo超镁铁质断层之后，在最后一次冰河期（LGM）期间伸展了一个冰叶。图像分析支持了这一假设：由于第IV周期的黄土色泽明显比其他色泽深，这与超镁铁质来源的来源相符。总之，各种应用技术使我们能够组合不同的信息，以便评估研究的黄土土的物理和形态特性，从而确定最可能的物质来源和风化途径。