Program
Earth and Planetary Sciences
College
Arts and Sciences
Student Level
Doctoral
Start Date
12-11-2020 4:00 PM
End Date
12-11-2020 5:00 PM
Abstract
Our planet has experienced roughly 14 glacial-interglacial cycles over its last one million years, undergoing fluctuations between cold ice ages and warm periods much like today. Archives of this paleoenvironmental change can be found in sediment cores and provide a means to observe environmental responses to various climate states and transitions. Here in the southwestern US, terrestrial climate records from ancient lakes are interrupted by desiccation during warm and dry interglacials. This has limited our knowledge of how past warm and dry periods have affected our land and therefore stymied more precise predictions of environmental conditions in a warmer and drier future. One environmental factor without a long-term record is an undeniable aspect of southwestern life, windblown dust. Climate variables not just related to wind are intimately involved in dust entrainment in source areas, transport across potentially vast distances, and ultimate deposition. Rainfall and temperature control the amount and type of vegetation on a landscape and the prevalence of roots, branches, and leaves which stabilize soils and baffle winds. The strength, duration, and seasonality of rainfall also influences erosive processes which expose fresh sediment to wind. A new core record from Stoneman Lake in central Arizona offers a unique and continuous view of the last ~1.2 million years. Among other aspects of the climate system this core is suited to address, the lake’s geologic situation allows the quantity of quartz in core sediment to be used as a measure of windblown dust accumulation, itself a proxy for climate in and around the major dust producing areas of the southwest. Elemental and grain size analyses can track changes in the input of locally eroded material and airborne sediment to the lake through time. X-ray probing of the atomic structure of clay minerals will offer insights into chemical weathering and the development of soils. Taken together, these data will address interrelationships among regional climate, weathering, erosion, and dust activity over an extensive and as-of-yet unresolved period in the southwest’s geologic history.
The Climatology of Windblown Dust over the Millennia in the American Southwest
Our planet has experienced roughly 14 glacial-interglacial cycles over its last one million years, undergoing fluctuations between cold ice ages and warm periods much like today. Archives of this paleoenvironmental change can be found in sediment cores and provide a means to observe environmental responses to various climate states and transitions. Here in the southwestern US, terrestrial climate records from ancient lakes are interrupted by desiccation during warm and dry interglacials. This has limited our knowledge of how past warm and dry periods have affected our land and therefore stymied more precise predictions of environmental conditions in a warmer and drier future. One environmental factor without a long-term record is an undeniable aspect of southwestern life, windblown dust. Climate variables not just related to wind are intimately involved in dust entrainment in source areas, transport across potentially vast distances, and ultimate deposition. Rainfall and temperature control the amount and type of vegetation on a landscape and the prevalence of roots, branches, and leaves which stabilize soils and baffle winds. The strength, duration, and seasonality of rainfall also influences erosive processes which expose fresh sediment to wind. A new core record from Stoneman Lake in central Arizona offers a unique and continuous view of the last ~1.2 million years. Among other aspects of the climate system this core is suited to address, the lake’s geologic situation allows the quantity of quartz in core sediment to be used as a measure of windblown dust accumulation, itself a proxy for climate in and around the major dust producing areas of the southwest. Elemental and grain size analyses can track changes in the input of locally eroded material and airborne sediment to the lake through time. X-ray probing of the atomic structure of clay minerals will offer insights into chemical weathering and the development of soils. Taken together, these data will address interrelationships among regional climate, weathering, erosion, and dust activity over an extensive and as-of-yet unresolved period in the southwest’s geologic history.
