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Southwestern North America is currently experiencing a multidecadal megadrought, with severe consequences for water resources. However, significant uncertainty remains about 21st century precipitation changes in this semi-arid region. Paleoclimatic records are essential for both contextualizing current change, and for helping constrain the sensitivity of regional hydroclimate to large-scale global climate. In this paper, we present a new 2.8 Ma to present compound-specific isotopic record from Clayton Valley, the site of a long-lived paleolake in the southern Great Basin. Hydrogen and carbon isotopes from terrestrial plant leaf waxes provide evidence of past shifts in rainfall seasonality as well as ecosystem structure, and help contextualize the formation of this lithium-rich lacustrine basin. Our results suggest that regional hydroclimates underwent a substantial reorganization at the Plio-Pleistocene boundary, especially between 2.6 and 2.0 Ma. In this interval, a reduced latitudinal temperature gradient in the North Pacific likely resulted in a northward shift in storm tracks, and a reduction in winter rainfall over the southern Great Basin. This occurred against a background of increased summer rainfall and a greater accumulation of lithium in the lake basin. Our interpretation is corroborated by a compilation of Plio-Pleistocene north Pacific sea surface temperature records, as well as an isotope-enabled model simulation. Overall, these results suggest that past shifts in rainfall seasonality helped set the stage for the development and dessication of lithium-rich lacustrine deposits.
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This content will become publicly available on January 22, 2026
Rock Magnetic Signature of Red Beds From the Intermontane Tarom Basin (NW Iran): Insights Into Middle to Late Miocene Environmental Conditions and Possible Forcing Mechanisms
Abstract The study of sedimentary magnetism in the intermontane Tarom Basin (northern Iran) offers insights into local paleoenvironmental conditions during global middle‐late Miocene climate changes and the topographic growth triggered by the Arabia‐Eurasia continental collision. Rock magnetic results reveal that the ∼16.2 to ∼10–9 Ma coarse‐grained deposits at the basin's southern margin present a homogenous magnetic mineral assemblage, reflecting sediment provenance. Conversely, the ∼13.2 to ∼7.6 Ma, fine‐grained deposits in the basin's depocenter include alternating playa‐lake and lacustrine deposits, recording dry, evaporative conditions, leading to hematite formation in a low‐temperature oxidizing environment, and wetter conditions that preserve the original detrital signal, respectively. Time series analyses show cyclicity in different period bands for magnetic susceptibility, but precession and obliquity cycles can hardly be resolved in the record. Comparison with deep‐sea oxygen isotope data suggests that from ∼13.2 to ∼10.8 Ma environmental conditions likely mirrored global climatic forcing, with lacustrine and playa‐lake deposits associated with increased and decreased global temperature, respectively. At ∼10.8 Ma, the basin likely recorded the Tortonian Thermal Maximum with the establishment of a lacustrine system. From ∼10.4 Ma, the magnetic susceptibility signal departed from the global climate record, possibly due to basin margin (western Alborz and Tarom mountains) and regional (Anatolian‐Iranian plateau) topographic growth, accompanied by increased precipitation seasonality, focused rainfall and augmented erosion rates. Finally, we suggest that before ∼10.8 Ma, the Hadley cells expanded northward, leading to a trade‐dominated system with moist air masses sourced from the Caspian, while from ∼10.8 Ma, westerlies dominance progressively prevailed.
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- Award ID(s):
- 2153786
- PAR ID:
- 10570661
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Paleoceanography and Paleoclimatology
- Volume:
- 40
- Issue:
- 1
- ISSN:
- 2572-4517
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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