Evolução dos processos de carstificação da formação Jandaíra, Bacia Potiguar, utilizando dados obtidos por LiDAR e VANT

Abstract

This research analyzes different types of karst landforms and their relationships with fracture systems, sedimentary bedding, and fluvial processes. We mapped karst features in Cretaceous carbonates of the Jandaíra Formation in the Potiguar Basin, Brazil. The study area is a semi-arid region, with low annual rainfall (600mm) and high evaporation (2000mm). We used high-resolution digital elevation models acquired by Light Detection and Ranging (LiDAR) and aerial ortophotographs acquired by unmanned aerial vehicle (UAV). This study focuses on surface and near surface process and grouped karst evolution into four stages. Fractures were opened by dissolution, which form vertical fluid pathways during stage 1 in a centimetric to metric scale. The most pervasive set of fracture concentrates the dissolution. Coeval intrastratal and interstratal dissolution occurred along horizontal layers, which bound dissolved fractures. This conduit system acted as pathways for water flow, which caused advanced leaching. The enlargement of conduits in subsurface contributed to the collapse of blocks, generation of sinkholes, and caves expansion in stage 2. During stage 3, propagation of horizontal and vertical dissolution along fractures and layers cause coalescence of sinkholes and capture of small streams. Fluvial processes dominate karst dissolution during stage 4, where alluvial sediments that caps the carbonate karst surface and fill caves and sinkholes along the valley. Tectonic and sedimentary bedding control all stages of karst evolution and resulting structures and landforms formed during these stages coexist. Comparisons with GPR, borehole and seismic surveys in sedimentary basins indicate that these structures are preserved after burial.