Multi-Scale Characterization of Joint Systems in Lihué Calel, La Pampa, Argentina: Integrating Structural Mapping and Shearlet-Based Image Analysis

We present an accessible MATLAB workflow for semi-automated fracture detection that streamlines a shearlet-based approach into a guided interface, adding tools for scale and orientation correction to enable the analysis of non-georeferenced field and satellite images with minimal user input. Applied at site, outcrop, and regional scales in the Lihué Calel Range (Argentina), the method replicates manual rose-diagram trends and spatial patterns while revealing additional fractures in overlooked “gray zones.” The integrated analysis defines a consistent joint network composed of two nearly orthogonal, subvertical master sets (D3: NW–SE; D4: NE–SW), a subhorizontal set dipping ~ 20°W (D5), and subordinate N–S (D1) and E–W (D2) sets. D3 and D4 are interpreted as Permian–Triassic oblique-extensional tectoclasis affecting Choiyoi ignimbrites, while D5, D1, and D2 reflect post-emplacement unloading and later Andean tilting. These sets explain Pollard and Aydin’s block classes and the structural control of ephemeral drainage, with D3 and regionally D2 guiding valley alignments. Methodologically, the algorithm is most sensitive to minimum contrast, wavelet support, and offset. Over-segmentation inflates joint counts and underestimates lengths, emphasizing the importance of parameter tuning and image quality. The workflow provides a scalable tool for preliminary mapping, quality control of manual digitization, and hypothesis testing, while clarifying the two-stage tectono-exhumational evolution of the Lihué Calel Range.