277-7 Rates and dates of loess deposition and soil formation on the Snake River Plain, Idaho, USA

Session: Critical Zone Science: Intersection of Processes Linked to Geomorphology, Ecology, Fire and Climate

Presenting Author:

Tanzila Hanif

Authors:

Hanif, Tanzila¹, Pierce, Jennifer², Huber, Dave³, Jin, Lixin⁴, Rittenour, Tammy M.⁵, Reynard, Linda M.⁶, Finstad, Kari⁷, Phillips, William M.⁸

Abstract:

Loess-paleosol sequences in eolian deposits on the Snake River Plain, Idaho, western US preserve records of Late Pleistocene to Holocene glacial-interglacial cycles. Here, we examine climate-driven changes in the timing and rate of loess accretion, soil formation, and pedogenic carbonate accumulation in the eastern and central Snake River Plain. High rates of loess deposition often correspond with dry, cold, and windy conditions and/or high sediment supply, while soil formation indicates landscape stability. Optically stimulated luminescence (OSL) dating of four loess-soil sequences provides a record of the timing of loess deposition, and radiocarbon dating (¹⁴C) of soil inorganic carbon (SIC) provides ages for soil formation and pedogenic carbonate precipitation. On the central Snake River Plain, marine isotope stage (MIS) 3 is marked by loess deposition between ~33 and 50 ka, and pedogenic carbonate accumulation between ~31 and 42 ka cal BP. During MIS 2, loess deposition between ~15 and 21 ka is contemporaneous with pedogenic carbonate precipitation. MIS 2 is characterized by diffuse pedogenic carbonate formation and rapid loess accumulation. Both the eastern and central Snake River Plain study sites experienced high rates of loess deposition during MIS 2; however, the eastern Snake River Plain had almost three times faster rates of loess accumulation (0.56-0.63 m/kyr from ~17-25 ka) as compared to the central Snake River Plain (0.18-0.26 m/kyr from ~15-21 ka). During MIS 1, loess deposition on the central Snake River Plain around ~11 ka was coincident with pedogenic carbonate formation ~10 ka cal BP. Soils developed during MIS 3 and MIS 1 are characterized by A horizons and well-developed Bk horizons, indicating soil stability and lower rates of loess accumulation during these intervals. This study highlights the role of Late Quaternary-scale climatic variability on rates and amounts of soil inorganic carbon storage.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7615

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