Regional geomorphological and gravimetric analysis of the Gualilán depression: An endorheic basin in the Andean Precordillera, Argentina

Abstract

This study provides the first integrated geomorphological and gravimetric assessment of the Gualilán depression, an endorheic basin located in the Central Precordillera of San Juan, Argentina. The basin covers 1463 km2 and is bounded by mountain ranges that strongly influence its hydrological and sedimentary dynamics. Three main morphostructural units were recognized: Mountainous, Piedmont, and Playa. Six river sub-basins were analyzed morphometrically, showing contrasts between the larger, north–south oriented western, northern, and southern sub-basins and the smaller, east–west oriented ones in the eastern sector. Digital elevation models and swath profiles reveal a marked asymmetry, with broader, gently sloping piedmonts in the west and narrower, steeper piedmonts in the east. This morphology reflects tectonic control associated with east-verging thrusts and dominant north–south reverse faults, further segmented by oblique NW–SE and SW–NE structures. Residual Bouguer anomaly analysis (XGM2019e) shows clear correlations between topography and subsurface geometry. Mountainous units are linked to positive anomalies up to +20 mGal, whereas piedmonts display negative values (0 to 20 mGal), indicating lower-density deposits and transitional domains. The Playa unit, with anomalies between -5 and +5 mGal, corresponds to alternating depocenters and areas of limited sediment accumulation. The results support the interpretation of the Gualilán depression as a closed continental piggyback basin that has functioned since at least the Cenozoic as a sediment reservoir. The integration of geomorphology, morphometry, and gravimetry highlights the role of inherited basement structures and neotectonic activity in shaping drainage patterns, sediment storage, and overall basin evolution within an actively deforming compressional orogen.