In deserts, the interplay between occasional fluvial events and persistent aeolian erosion can form composite modern and relict surfaces, especially on the distal portion of alluvial fans. There, relief inversion of alluvial deposits by differential erosion can form longitudinal ridges. We identified two distinct ridge types formed by relief inversion on converging alluvial fans in the hyperarid Chilean Atacama Desert. Although they are co-located and similar in scale, the ridge types have different ages and formation histories that apparently correspond to minor paleoclimate variations. Gravel-armored ridges are remnants of deflated alluvial deposits with a bimodal sediment distribution (gravel and sand) dated to a minor pluvial phase at the end of the Late Pleistocene (~12 kyr). In contrast, younger (~9 kyr) sulfate-capped ridges formed during a minor arid phase with evaporite deposition in a pre-existing channel that armored the underlying deposits. Collectively, inverted channels at Salar de Llamara resulted from multiple episodes of surface overland flow and standing water spanning several thousand years. Based on ridge relief and age, the minimum long-term deflation rate is 0.1–0.2 m/kyr, driven primarily by wind erosion. This case study is an example of the equifinality concept whereby different processes lead to similar landforms. The complex history of the two ridge types can only be generally constrained in remotely sensed data. In situ observations are required to discern the specifics of the aqueous history, including the flow type, magnitude, sequence, and paleoenvironment. These findings have relevance for interpreting similar landforms on Mars.

在沙漠中，偶然的河流事件和持续的风蚀作用之间的相互作用可以形成复合的现代和残余表面，特别是在冲积扇的远端部分。在那里，由差异侵蚀引起的冲积沉积物的浮雕反转可以形成纵向脊。我们确定了两种不同的山脊类型，这些山脊类型是由在超干旱的智利阿塔卡马沙漠中汇聚的冲积扇上的地貌反演形成的。尽管它们位于同一地点且规模相似，但这些山脊类型具有不同的年龄和形成历史，显然对应于较小的古气候变化。砾石铠装山脊是具有双峰沉积物分布（砾石和沙子）的瘪的冲积沉积物的残余物，其年代可追溯到晚更新世末期（~12 kyr）的小雨洪阶段。相比之下，较年轻的 (~9 kyr) 硫酸盐覆盖的山脊形成于次要干旱阶段，蒸发岩沉积在预先存在的通道中，为下面的沉积物提供保护。总体而言，拉马拉盐沼的倒置河道是由跨越数千年的多次地表地表流和积水造成的。根据山脊起伏和年龄，最低长期紧缩率为 0.1-0.2 m/kyr，主要由风蚀驱动。这个案例研究是等值概念的一个例子，不同的过程会导致相似的地貌。两种脊类型的复杂历史只能在遥感数据中得到普遍约束。需要原位观察来辨别水历史的细节，包括流动类型、大小、序列和古环境。