Evidence for strong relations between the upper Tagus loess formation (central Iberia) and the marine atmosphere off the Iberian margin during the last glacial period

Abstract

During glacial times, the North Atlantic region was affected by serious climate changes corresponding to Dansgaard-Oeschger cycles that were linked to dramatic shifts in sea temperature and moisture transfer to the continents. However, considerable efforts are still needed to understand the effects of these shifts on terrestrial environments. In this context, the Iberian Peninsula is particularly interesting because of its close proximity to the North Atlantic, although the Iberian interior lacks paleoenvironmental information so far because suitable archives are rare. Here we provide an accurate impression of the last glacial environmental developments in central Iberia based on comprehensive investigations using the upper Tagus loess record. A multi-proxy approach revealed that phases of loess formation during Marine Isotope Stage (MIS) 2 (and upper MIS 3) were linked to utmost aridity, coldness, and highest wind strengths in line with the most intense Greenland stadials also including Heinrich Events 3–1. Lack of loess deposition during the global last glacial maximum (LGM) suggests milder conditions, which agrees with less-cold sea surface temperatures (SST) off the Iberian margin. Our results demonstrate that geomorphological system behavior in central Iberia is highly sensitive to North Atlantic SST fluctuations, thus enabling us to reconstruct a detailed hydrological model in relation to marine–atmospheric circulation patterns.

Last glacial loess dynamics in the Southern Caucasus (NE-Armenia) and the phenomenon of missing loess deposition during MIS-2

“…Similar relationships between loess deposition (glacier advances) and stronger aridity (higher moisture availability) have been documented for loess deposits in the nowadays semi-arid interior of Iberia 8 , or in semi-arid basins in central Asia with direct connection to the Tian Shan Mountains 16 . Therefore, we suggest that loess formation in the mid latitude Mediterranean belt and eastern adjoining semi-arid regions is mostly sensitive to higher aridity rather than to lower temperatures 1 .…”

“…For instance, periods of strengthened East Asian Winter Monsoon (EAWM), reflected by grain-size coarsening in loess sections of the Chinese Loess Plateau (CLP), correlate with North Atlantic climate events 63 – 65 . Such North Atlantic climate events are likewise demonstrated in LPS in Europe 7 , 8 , 66 – 68 . The EAWM is driven by the SH 10 that, in turn, gains strength from cold air supply from Arctic regions such as the Nordic and Barents Seas 65 .…”

“…7 a) coincides with the early MIS-4 that was characterized by lowest northern hemisphere summer insolation 70 . This cold phase of large-scale regional dryness 71 was accompanied by massive loess deposition in large parts of Eurasia 8 , 15 , 19 , 72 – 75 as well as intensified aeolian dynamics on the CLP (Fig. 7 i,j) 65 .…”

“…Owing to remarkable progress in the field of age determination, litho-/pedostratigraphic features in LPS can be linked to millennial to centennial-scale climate variations 3 , 4 . This is exemplified by impacts of Dansgaard-Oeschger (DO) oscillations in the North Atlantic on climate and environmental changes in Western and Eastern Europe 3 – 8 . Likewise, regarding different Asian regions a teleconnection to North Atlantic patterns is widely accepted, e.g.…”

Source areas of the Eastern Ebro Valley loess (NE Iberian Peninsula): Heavy mineral composition as a provenance indicator

“…This dynamic is due to a heavy mineral depletion by weight sorting and the contributions of aeolian material from other areas, such as Miocene substrate interfluves with a lower heavy mineral concentration. The Ebro Valley loess %HM is higher than for other European loess(Chmielowska & Salata, 2020;Wolf et al, 2019Wolf et al, , 2021, except in the case of Pannonian Basin, with which they were very similar(Tham o-Bozs o et al, 2014).There was an enrichment in zircon and inosilicates in the loess compared to the terraces, and a certain impoverishment in staurolite.Zircon enrichment in loess could be explained by the preference for lower diameters during wind transport and a possible contribution from Miocene sandstones. Zircon crystals (50-70 μm) are found in the smallest particle sizes of fluvial terraces (average size 180-200 μm), favouring wind entrainment.…”