Holocene records of eolian dust deposition from high‐elevation lakes in the Uinta Mountains, Utah, USA

Abstract

Radiocarbon-dated sediment cores from subalpine lakes were used to investigate post-glacial dust deposition in the Uinta Mountains (Utah, USA). Lake sediments were geochemically characterized with ICP-OES, ICP-MS and XRF core scanning. Collections from passive samplers constrain the properties of modern dust, and samples of regolith constrain properties of the local material within the watershed. Ca and Eu are more abundant in dust, whereas Ti and Zr are more abundant in local regolith. As a result, the Ca/Ti and Eu/Zr ratios are indices for the dust content of lake sediment. In all records, the dust index rises in the early Holocene as watersheds became stabilized with vegetation, reducing the influx of local material. After this point, values remained above average through the middle Holocene, consistent with an increased dust content in the sediment. Dust index values drop in the late Holocene in most lakes, suggesting a decrease in dust abundance. Generally synchronous shifts in dust index values in cores from lakes in different parts of this mountain range are evidence of enhanced dust deposition in this region during the middle Holocene, and are consistent with a variety of records for increased aridity in the southwestern USA at this time.

Mineral Dust and Pedogenesis in the Alpine Critical Zone

“…Statistical analysis reveals that the average amount of extractable Ca in the soils is strongly and positively correlated with the average amount of mineral Ca in the dust, and base saturation in these soils is dominated by Ca (Table 2). As noted above, ratios of elemental abundance in dust/rock and soil/rock reveal that Ca content is greatly elevated in the dust, an observation corroborated by previous work (Munroe et al, 2021a). The wet technique used in this study to remove dust from the collectors might dissolve fine-grained calcite, making it difficult to assess whether calcite is present in the dust, as reported in previous studies (Litaor, 1987).…”

“…The primary implication of this conclusion is that future changes in dust flux will have corresponding effects on future soil formation in the mountain CZ. Studies utilizing lake sediment archives have demonstrated that dust fluxes to parts of the Rocky Mountains have changed during the Holocene, likely in response to climatic factors (Arcusa et al, 2020;Routson et al, 2016Routson et al, , 2019Munroe et al, 2021a), so dust flux should not be expected to be invariant. This realization is concerning for two reasons.…”