Rectangular drainage pattern evolution controlled by pipe cave collapse along clastic dikes, the Dead Sea Basin, Israel

Abstract

Rectangular drainage networks are characterized by right-angle bends and confluences. The formation of such patterns is commonly associated with orthogonal sets of fractures, making them an outstanding example for structurally controlled landform evolution. However, this association remains largely circumstantial because little is known about how rectangular drainages mechanistically link to orthogonal fractures. We investigated these linkages in the hyper-arid Ami'az Plain located within the Dead Sea Basin in Israel. The Ami'az Plain is incised by a rectangular canyon system and is penetrated by hundreds of sub-vertical clastic dikes (mode-I fractures infilled with sediments). Numerous caves extend from the banks and heads of the canyon system. Based on field surveys and analysis of a high-resolution LiDAR data, we mapped the Ami'az Plain drainage network and its associated geomorphic landforms including sinkholes. Our analysis revealed that the subaerial tributaries of the canyon system share dominant orientations with the strike of the clastic dikes. In addition, subsurface mapping assisted by Ground scanning LiDAR, together with field experiments, demonstrated that the caves and sinkholes in the Ami'az Plain are spatially associated with clastic dikes and that the caves formed by piping erosion along dikes. Based on these findings, we suggest that clastic dikes act as efficient infiltration pathways to the subsurface, and subsurface flow along clastic dikes induces internal erosion that forms pipe caves. The sinkholes form by collapses of cave roofs. Coalescence of sinkholes and seepage erosion where dikes intersect canyon heads generate new tributaries and act to extend existing ones. Fluvial erosion and bank collapse modify the drainage network. Our findings emphasize the critical role of subsurface erosion, caves and sinkholes in linking fractures to drainage pattern evolution, and provide new process-based framework to interpret rectangular drainage networks on Earth and other planetary surfaces.