2010). In fact, corresponding environmental conditions have 
been documented for periods linked to Greenland stadials 
and particularly to Heinrich stadials in many places on the 
ıberian Peninsula (e.g., Gonzälez-Samperiz et al., 2006, 
2010; Sepulchre et al., 2007; Fletcher and Sänchez Goni, 
2008; Vegas et al., 2010; Moreno et al., 2012, 2014; Dennis- 
ton et al., 2018). Underlying mechanisms are seen in specific 
land-sea relationships initiated by a decrease of sea surface 
temperatures linked to a southward incursion of the polar 
front over the Iberian margin (Roucoux et al., 2005; Sänchez 
Gofi et al., 2008; Eynaud et al., 2009; Martin-Garcia, 2019). 
This resulted in reduced moisture uptake off the Iberian coast 
and thus, reduced moisture transfer over the Iberian Penin- 
sula (e.g., Denniston et al., 2018; Budsky et al., 2019; Torner 
st al., 2019; see Genty et al., 2003 for SW France). Evidence 
for corresponding changes of atmospheric circulation pat- 
terns in the course of D-O cycles were likewise found by 
Moreno et al. (2005), and also Florineth and Schlüchter 
(2000), who discussed a shift of westerly storm tracks over 
the southern tip of Iberia during cold stages of MIS 2 in 
accordance with a southward shift of the polar front (see 
also Pailler and Bard, 2002; Roucoux et al., 2005; Colombu 
et al., 2020). 
Based on the loess sections and the proxy information con- 
tained therein, conclusions concerning dominant wind direc- 
tions seem difficult. For example, grain size and heavy 
mineral results suggest the prevalence of strong, turbulent, 
surface winds that may have been predetermined by local 
topography and relief (Wolf et al., 2019). Nonetheless, a 
general prevalence of west-east oriented winds is still likely, 
all the more so when considering that most loess deposits in 
the upper Tagus Basin are situated on eastwardly exposed 
(and presumably leeward) slope positions of dissected 
Tagus valley flanks. 
Beside these relationships, it is still an open question as to 
why loess dynamics during middle MIS 3 displayed a 
completely deviating pattern without loess formation during 
the most pronounced cold spells of GS-9/HS4 and GS-13/ 
HS5, but instead loess formed in a period between these 
cold spells. Paleoenvironmental archives in Iberia and marine 
records along the Iberian margin generally do not show indi- 
cations of very cold and arid conditions linked to GS-12, 
GS-11, or GS-10 (e.g., Sänchez Gofil et al., 2008; Moreno 
at al., 2012), when the loess unit SU-6 was formed. In turn, 
these stadials were much more pronounced in central Europe 
(Kjellström et al., 2010; Staubwasser et al., 2018) and SW 
France (Genty et al., 2003). On the other hand, GS-9 was 
less prominent in central Europe, but is reflected as the 
most intense cold period in the western Mediterranean, with 
a strong influence on inland environments in central and 
southern Iberia (Sepulchre et al., 2007; Eynaud et al., 2009; 
Staubwasser et al., 2018). Thus far, we are not able to provide 
a conclusive explanation regarding these patterns, but assume 
that climate as a main driver of geomorphic system dynamics 
may have been superimposed upon by other (perhaps local) 
factors. Below, we give a detailed characterization of SU-6 
based on extensive proxy information. 
„ 
D. Wolf et al. 
Paleoenvironmental reconstructions based on proxy 
information from the upper Tagus loess record 
Temperature and wind strength reconstruction as 
inferred from heavy mineral analyses and grain-size 
distributions 
increasing heavy mineral concentration (HMC) and fine sand 
contents in the key sections of Paraiso and Villarubia point to 
gradually increasing wind strength over the last glacial 
period, with a maximum during GS-5/H$S3 and high values 
for GS-3/HS2 and GS-2.1a/HS1. During MIS 4, wind 
strengths were reduced, while another maximum appeared 
in a period around GS-10 to GS-12. We relate these peak 
phases of gustiness with a higher frequency and magnitude 
of traversing storms due to a shift of the main storm tracks 
over central Iberia (between 35°N and 42°N; Naughton 
et al., 2009; Pinto and Ludwig, 2020) due to higher meridio- 
nal temperature and atmospheric pressure gradients over the 
eastern North Atlantic, especially during Heinrich stadials 
‘Roucoux et al., 2005). Likewise, local high- or low-pressure 
cells that were formed by strong cooling in winter or high 
insolation during summer over the flat plains of the Iberian 
Meseta may have caused stronger winds in the upper Tagus 
Basin (Lautensach, 1964). The real novelty is that GS-5/ 
HS3 appears as the phase with the highest storm activity, 
which is also obvious from the highest loess accumulation 
for the complete last glacial period (Fig. 14). Although HS3 
has been frequently documented in marine records around 
the Iberian Peninsula (e.g., Cacho et al., 1999; de Abreu 
et al., 2003) there is only sporadic evidence in terrestrial 
archives (e.g., Gonzälez-Samperiz et al., 2006; Löpez-Garcfa 
et al., 2014). Based on 15 sediment cores from the Iberian 
margin, Salgueiro et al. (2014) observed a particular cooling 
and drop in productivity during HS3 (and HS1), reflecting the 
most extreme southward extension of cold waters. The 
corresponding strong SST gradient along the Iberian margin 
‘=6°C) is in line with our interpretation of a shift in storm 
racks. 
Using heavy mineral analyses, we deduce that during the 
ıpper MIS 3, Tagus River floodplain sediments became 
‘he main source for loess formation as indicated by a three- 
fold increase of dolomite in loess layer SU-7. This, in turn, 
demonstrates a considerable increase in sediment supply 
from the Iberian Range and Sierra de Altomira (Fig. 13), 
where intensified (periglacial) weathering and erosion 
dynamics were presumably initiated by cold environmental 
conditions. This means that periglacial processes were lim- 
ited during the first stages of the last glacial period as evi- 
denced by only a minor contribution of Tagus River 
floodplain sediments to the loess sections. Thus, we 
assume less cold conditions during MIS 5, MIS 4, and dur- 
ing GS-12 to GS-10. Periglacial mountain processes 
strongly increased during the course of GS-5/HS3 and 
‚emained at a high level during GS-3/HS2 and GS-2.1a/ 
HS1, evidence of cold conditions at least in the mountain 
ranges. 
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