Holocene atmospheric dust deposition in NW Spain

Abstract

Atmospheric dust plays an important role in terrestrial and marine ecosystems, particularly those that are nutrient limited. Despite that most dust originates from arid and semi-arid regions, recent research has shown that past dust events may have been involved in boosting productivity in nutrient-poor peatlands. We investigated dust deposition in a mid-latitude, raised bog, which is surrounded by a complex geology (paragneiss/schist, granite, quartzite and granodiorite). As proxies for dust fluxes, we used accumulation rates of trace (Ti, Zr, Rb, Sr and Y) as well as major (K and Ca) lithogenic elements. The oldest, largest dust deposition event occurred between ~8.6 and ~7.4 ka BP, peaking at ~8.1 ka BP (most probably the 8.2 ka BP event). The event had a large impact on the evolution of the mire, which subsequently transitioned from a fen into a raised bog in ~1500 years. From ~6.7 to ~4.0 ka BP, fluxes were very low, coeval with mid-Holocene forest stability and maximum extent. In the late Holocene, after ~4.0 ka BP, dust events became more prevalent with relatively major deposition at ~3.2–2.5, ~1.4 ka BP and ~0.35–0.05 ka BP, and minor peaks at ~4.0–3.7, ~1.7, ~1.10–0.95 ka BP and ~0.74–0.58 ka BP. Strontium fluxes display a similar pattern between ~11 and ~6.7 ka BP but then became decoupled from the other elements from the mid Holocene onwards. This seems to be a specific signal of the granodiorite batholith, which has an Sr anomaly. The reconstructed variations in dust fluxes bear a strong climatic imprint, probably related to storminess controlled by North Atlantic Oscillation conditions. Complex interactions also arise because of increased pressure from human activities.

Storm chasing: Tracking Holocene storminess in southern Sweden using mineral proxies from inland and coastal peat bogs

“…Halogens have been used as indicators of increased sea salt spray during storms (Orme et al, 2015;Stewart et al, 2017), although this has not shown to be universally applicable (Kylander et al, 2020). Multi-element approaches have also revealed changes in the source, grain size and magnitude of minerals being deposited on bogs through, for example, Si/Al ratios and elemental MAR (Kylander et al, 2020;Martinez-Cortizas et al, 2020;Sj€ ostr€ om et al, 2022).…”

Chronology of geomorphological changes in a cantabrian mountain valley over the last 20,000 years.

“…The 8.2 ky BP event has not been detected, although it has been found several times in the N and NW Iberian Peninsula (González-Amuchástegui and Martínez-Cortizas et al, 2020). The homogeneity of AC-4 layer indicates that from 10.2 -10.1 ky BP.…”

Characterization of Atmospheric Deposition as the Only Mineral Matter Input to Ombrotrophic Bog

“…Peatlands are specific anoxic and acidic environments that have the potential to retain and store large amounts of major and trace elements [1,2]. Ombrotrophic peatlands are limited to the atmosphere as a source of water and mineral matter [3,4], and are believed to be good geochemical archives of air quality over the past centuries [1,5,6]. This is based on the assumption that trace elements are immobile in the peat matrix and that accumulation in the record represents a direct measure of atmospheric deposition [7,8].…”