The precise determination of landforms and their formation processes are key to accomplish detailed soil mapping and better understand of soil genesis. The Upper General River Basin is located at the southeast of Costa Rica on the transition between Cordillera de Talamanca and General River Valley, forming an extensive alluvial fan sequence. Our work aims to determine the soil–geomorphology relationships on these alluvial fans. The methods employed consisted of geomorphological mapping using 1:25,000 aerial photographs to determine five alluvial fans: buried inactive, modeled inactive, early, intermediate, and late. Soil maps were established by combining landforms with soil survey data that allowed to differentiate twelve soil units of Ultisols associated with Oxisols, Inceptisols and Entisols. The most weathered soils were classified as Anionic and were Acrustox found on the oldest landforms located on buried inactive and early alluvial fans. These soils were found associated with Typic Rhodustults and Ustic Haplohumults. Typic Ustifluvents occurred on early alluvial fans and modeled inactive alluvial fans. Similar morphologic and chemical characteristics of the evaluated Oxisols were found for soils previously classified as Ultisols. These findings support the hypothesis that many soil currently classified as Ultisols could be reclassified as Oxisols (if the appropriate mineralogical analyses were conducted). These results put in perspective that the origin of the fans and hence their ages control the consequent soil development. In addition, the study contextualizes the implications of mapping and classifying highly weathered tropical soils for territorial planning, agricultural management and natural resources conservation.

精确确定地貌及其形成过程是完成详细的土壤测绘和更好地了解土壤成因的关键。上将军河流域位于哥斯达黎加的东南部，在塔拉曼卡山脉和将军河谷之间过渡，形成了广泛的冲积扇序列。我们的工作旨在确定这些冲积扇上土壤与地貌的关系。所采用的方法包括使用1：25,000的航拍照片进行地貌制图，以确定五个冲积扇：埋没的非活动性，建模的非活动性，早期，中期和晚期。通过将地貌与土壤调查数据相结合来建立土壤图，从而可以区分十二种土壤单位，其中与尿溶胶，承兑溶胶和恩替酚相关。风化最严重的土壤被归类为阴离子土壤，是在埋藏的非活动和早期冲积扇上最古老的地貌上发现的Acrustox。这些土壤被发现与典型的Rhodustults和Ustic Haplohumults相关。典型的Ustifluvents发生在早期的冲积扇上，并模拟了不活跃的冲积扇。对于先前分类为Ultisols的土壤，发现了评估的Oxisols具有相似的形态和化学特征。这些发现支持以下假设：当前分类为Ultisols的许多土壤可以重新分类为Oxisols（如果进行了适当的矿物学分析）。这些结果表明，风扇的起源以及它们的年龄控制着随之而来的土壤发育。此外，