Distributive Fluvial Systems (DFS) are fan-shaped landforms constituted by a radial system of channels that diverge downstream from an active apex, where the drainage emerges from the confinement valley. In such landforms, elevation, distance from fluvial channels, sedimentation rates, surface stability, and plant cover control weathering processes and soil development, but these features are obliterated within geological time. Thus, the micromorphological analysis of paleosols can be helpful for paleoenvironmental reconstruction of ancient DFS, improving the knowledge of soil genesis in these depositional landforms. Here, we describe macro and micromorphological features of twenty paleosols developed under arid to semiarid climates along the proximal to the medial zone of an Upper Cretaceous DFS in the Marília Formation, Bauru Basin, Brazil. Paleosols on the proximal zone typically showed features consistent with poor drainage, namely Bg, Btg and Bss horizons, and reddish Bt horizons in higher positions. Conversely, paleosols on the medial zone commonly showed reddish colours and pronounced secondary carbonate accumulation, consistent with a predominantly arid climate. Based on this distribution, we elaborated an evolution landscape model for the proximal and medial zone of the Bauru DFS, including allogenic and authigenic controls of soil development during the Campanian to the Maastrichtian epochs of southeastern Brazil.

分配河流系统（DFS）是由径向河道系统构成的扇形地貌，这些河道从活动顶点向下游发散，排水系统从活动顶点流出。在这种地貌中，海拔、距河道的距离、沉积速率、表面稳定性和植物覆盖控制着风化过程和土壤发育，但这些特征在地质时间内就被消除了。因此，古土壤的微形态分析有助于古代DFS的古环境重建，提高对这些沉积地貌土壤成因的认识。在这里，我们描述了巴西巴乌鲁盆地马里利亚组上白垩统DFS内侧带近端在干旱至半干旱气候下发育的 20 个古土壤的宏观和微观形态特征。近端区域的古土壤通常表现出与排水不良一致的特征，即 Bg、Btg 和 Bss 层位，以及较高位置的淡红色 Bt 层位。相反，内侧区域的古土壤通常呈现微红色和明显的次生碳酸盐堆积，与主要干旱的气候一致。基于这种分布，我们详细阐述了巴乌鲁 DFS 近端和中间区域的演化景观模型，包括巴西东南部坎帕阶到马斯特里赫特阶期间土壤发育的异源和自生控制。