X 
paleoclimatic and paleohydrological changes may arise from 
compound-specific 8'°C analyses on the same samples. 
Because all 81°C wrax values are in the range of published Cz 
plant waxes, we conclude that there was a reduced influence 
of C, plants during the last glacial period. Moreover, the 
8RC wax variations in the loess section do not correlate with 
the pattern of the atmospheric CO, curve. Thus, the basic 
assumption is that varlations in 8RCwax in the Paraiso section 
were most likely controlled by water availability, 1.e., precip- 
itation and relative humidity. According to plant physiologi- 
cal processes, the incorporation of carbon into plant leaves, 
and thus the significance of our 81°C wrax moisture record, is 
highest during the vegetation period. However, because the 
moisture budget in the Mediterranean is a result of complex 
relations between, e.g., atmospheric moisture content, atmo- 
spheric circulation patterns, evaporation from the sea and 
over land, etc. (see D’Agostino and Lionello. 2020), state- 
ments about the last glacial rainfall distribution over a year 
or seasonal effects are not feasible at this time. Accordingly, 
we assume that the decrease of 8*° Con during MIS 4 (SU-5) 
indicates a trend to generally less arid conditions, while SU-6 
shows significant increase of 8'°C (Fig. 9), reflecting gener- 
ally higher aridity. We expect that the formation of SU-6 
may have been linked to so-far unprecedented aridity in the 
ıberian interior because 81°C wax values of more than —-30%o 
surpass the values of all previous phases. After maximum val- 
ues appear in SU-7 (end of MIS 3, beginning of MIS 2), 
a trend to more depleted values in SU-8 indicates less arid 
conditions during the middle MIS 2 (Fig. 9). 
Provenience of loess deposits 
Based on heavy mineral analyses on different loess sections 
and representative samples from potential source areas, we 
were able to identify adjacent river floodplains as the most 
likely local loess sources. Moreover, the contribution of the 
different sources changed over time, enabling reconstruction 
of regional paleoenvironmental changes. A summary of the 
heavy mineral results is presented here (for more information, 
see Wolf et al., 2019). 
In total, 42 samples were analyzed from five different loess 
sections. Another seven samples were taken from potential 
source regions: (i) Tertiary marls that mark the underlying 
substrate of all loess deposits (gypsum marl in Fig. 13); (1) 
Paleozoic metamorphic and granitic rocks located west of 
the loess deposits (represented by Algodor River sediments; 
see Fig. 1); and (iii) Mesozoic sedimentary rocks east of the 
study area (represented by Tagus River sediments; see Fig. 1). 
The most important findings are that the reference samples 
show significant changes in heavy mineral composition and 
heavy mineral concentration (HMC). Marls show the lowest 
soncentrations (HMC = 0.04%) and are characterized by a 
dominance of apatite minerals. Paleozoic rocks (Algodor 
River sediments) reveal highest values for HMC (0.51—- 
0.78%) and are characterized by higher garnet contents. 
Finally, Mesozoic rocks (Tagus River sediments) show a 
HMC between 0.08-0.13%, and are represented by higher 
D. Wolf et al. 
tourmaline contents, and only these samples showed an 
admixture of dolomite minerals. 
While the heavy mineral composition of the loess sam- 
ples is quite similar, the proportions of the different trace 
minerals show significant variation. As shown in the ternary 
Jdiagram in Fig. 13A, samples from the same loess section 
plot generally close together, while different sections 
3how a considerably higher scatter. This indicates marginal 
homogenization of the sediments during aeolian transport, 
pointing to different local sources and short transport dis- 
:ances. Moreover, there are strong similarities between dom- 
inant trace minerals in individual loess sections and the 
closest local source (Algodor River floodplain vs. Tagus 
River floodplain vs. marls). However, due to methodologi- 
cal limitations, grains smaller than 40 um could not be ana- 
Iyzed, and statements on the origin of medium and fine silt 
are not feasible as of yet. 
Samples with higher proportions of apatite that are consid- 
ered as evidence for a more intense admixture of marl substra- 
um belong, without exception, to unit SU-3, which further 
strengthens the scenario that SU-3 is comprised of soil sedi- 
ments derived from surface erosion of surrounding marl 
areas. In addition, a recent flood loam sample from the Algo- 
dor River floodplain shows high apatite content, clearly dem- 
Onstrating that these cohesive floodplain deposits originate 
from soil erosion of the surrounding marl slopes. 
The Paraiso section reveals a general increase of HMC 
from bottom to top, in line with increasing fine sand contents. 
Because this section is considered to be a key section for ana- 
(yzing aeolian transport processes due to its more distant loca- 
‘1on from the river floodplain, this trend points to an 
increasing wind strength over the last glacial period. More- 
over, in the Parafso section, changes in the dominant sedi- 
ment source appear, beginning with sediment contributions 
from a certain portion of Paleozoic rocks (Algodor River sed- 
iments) during MIS 5, to a dominance of sediments from the 
Tagus River floodplain during MIS 3, and finally to an exclu- 
sive contribution of Tagus floodplain sediments during the 
end of MIS 3 and MIS 2 (Figs. 9, 13B). This might indicate 
ı change from dominant west winds during the early glacial 
period towards a stronger effect of close-to-ground winds. 
Alternatively, this might indicate a strong increase in fluvial 
sediment supply from the Iberian Range. The transition 
from middle MIS 3 (SU-6) to upper MIS 3 (SU-7) is charac- 
‚erized by a three-fold increase of HMC and dolomite, point- 
ing to a strong increase in the amount of material that was 
deflated from the floodplain. Therefore, apart from increasing 
wind strength, we likewise expect a stronger supply of fluvial 
sediments to the Tagus River floodplain starting from the 
upper MIS 3. 
Spatial aspects of loess characteristics 
As already discussed, the base (SU-3) of all sections located 
on the middle to late Pleistocene terrace level (Fuentiduena, 
A3, Villamanrique) is characterized by relocated material 
derived from catchment erosion. Likewise, unit SU-4 shows 
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