Magnetic and Granulometric Insights Into Dust Deposition Mechanisms in the Pampean Plains and Elevated Loess of Argentina

Abstract

Pampean loess represents one of the most important terrestrial sedimentary archives of climate change in the Southern Hemisphere, providing information on past dust dynamics and wind circulation patterns over the last million years. This article complements previous work on the loess deposits of the Pampean Plains by presenting new high-resolution magnetic suscepti- bility and grain-size data for two high-elevation loess–paleosol sections in the Sub-Andean Ranges and Sierras Pampeanas Plateau of Argentina. High background magnetic susceptibility is attributed to the andesitic and basaltic composition of the source rocks. Field observations, magnetic susceptibility and grain-size analyses highlight distinct loess–paleosol layers preserved within the high-elevation sections, contrasting with the more homogenous deposits of the lowland Pampean Plains. Grain-size distributions are multimodal on the plains, linked to diverse dust sources and wet deposition under humid conditions, while fine subpopu- lations dominate in high-elevation sections, reflecting subtropical jet stream-driven dry deposition. Magnetic susceptibility anal- ysis suggests possible wind-vigour enhancement from intensified wind strength in loess from the Sierras Pampeanas Plateau, while pedogenic enhancement and magnetic depletion from weathering is observed in loess from the Sub-Andean Ranges. These findings emphasise the role of topography and atmospheric dynamics in shaping aeolian sediment records.