The influence of landslides on anticline breaching and landscape evolution in the Appalachian Valley and Ridge

The evolution of landscapes over time is governed by autogenic processes, such as sediment dynamics and landslides, and allogenic processes and factors, such as tectonics and lithology. The style of tectonic deformation governs the spatiotemporal distribution of rock types exposed at Earth’s surface, controlling how surface processes shape the landscape. The evolution of lithologically complex landscapes like fold-and-thrust belts remains incompletely understood because it is not clear how lithology affects the interactions between, and relative dominance of, different surface processes. The Appalachian Valley and Ridge physiographic province, an ancient fold-and-thrust belt, provides a unique natural laboratory for studying the interplay among tectonics, lithology, and surface processes. The region's diverse lithology is vividly displayed in exposed, breached anticlines, where resistant sandstones form ridges, and more erodible or weatherable carbonates and shales form valley bottoms in anticline cores. Breaching occurs when the crest is eroded, exposing deeper, often weaker layers. The mechanisms behind anticline breaching and breach expansion are not well understood and could be triggered by large episodic events, such as landslides, more gradual processes such as fluvial incision, or a combination of the two. In this study, we set up a landscape evolution model mimicking the evolution of Appalachian landscapes to investigate how autogenic interactions among fluvial incision, sediment dynamics, and landsliding respond to the lithological and structural variability found in ancient fold-and-thrust belts like the Appalachian Valley and Ridge province. We explore landscape evolution through a series of modeling experiments and develop new metrics to capture the dynamics of breached-anticline systems. By comparing metrics between modeled and real landscapes, we quantify the role of episodic landsliding in controlling anticline breaching and the dynamic evolution of tectonically inactive landscapes where the spatial distribution of different rock types governs landscape evolution.