Windblown dust from southern South America plays a significant role in regional and global systems by delivering micronutrients and important trace metals like iron to the Southern Atlantic Ocean. Dust from South America facilitates marine phytoplankton productivity, which reduces atmospheric CO2 levels and impacts global temperatures. This project investigated loess (windblown dust) deposits in Argentina. The intellectual merit of this work resides in understanding the source locations of windblown dust, the causes behind dust production, the relationship between regional rivers and windblown dust, and the multi-million year history of wind-transported dust throughout southern South America.

Using single-grain provenance (origin) techniques on minerals like zircon this study demonstrated that several distinct sediment source locations in the southern Andes play dominant roles in supplying windblown dust. The expansive dust deposits in central Argentina and surrounding regions are divisible by the zircon grains that record the original source location of the dust grains, meaning that dust in one part of Argentina can be distinguished from identical dust in an adjacent area. This study showed that the rivers exiting the southern Andes are critical for transporting sand and dust to the low-elevation regions in front of the Andes, where the dust is entrained by regional and local winds. Although windy and arid conditions are necessary to blow the dust into the South Atlantic Ocean, there needs to be sufficient precipitation to maintain river flow from the mountains to the low-elevation plains in order to provide a steady supply of sand and dust. Based on the dust deposits in northern Argentina, wind patterns across the Puna Plateau in northern Argentina and Chile have changed over time, reflecting northward migration of westerly winds during colder periods in the earth’s history.

Because dust in southern South America is important for marine phytoplankton productivity, which can impact global climate, it is critical to determine when and how the windblown transport of dust in this region began. This study was able to demonstrate that significant deposits of windblown dust appear in southern South America approximately 6.5 million years ago and were derived from the same locations as the dust in modern settings. The initiation of wind-transported dust corresponds to a period of global cooling and a change in atmosphere circulation that produced more arid conditions in southern South America. Based on the results of this study, the global cooling trend that initiated greater windblown dust activity in southern South America led to more arid conditions, a greater influx of micronutrients to the South Atlantic Ocean, increased phytoplankton production and higher rates of CO2 drawdown. Thus it is likely that the global cooling event between 7 and 5 million years ago sparked conditions and processes in South America that resulted in even cooler global temperatures.

This study produced graduate theses, conference presentations and peer-reviewed publications and also served as the core of numerous informal presentations at public outreach events. Two master’s students and eight undergraduate students at the University of South Carolina were supported by this research. Collaborations with three Argentine institutions were initiated and currently involve multiple Argentine researchers.

Last Modified: 10/11/2024
Modified by: Andrew Leier