Upper Tagus loess formation and the marine atmosphere off the Iberian margin 
A3 section upper part 
ISLages SU 
ka] 
Sof Coarse sIk contenl (%)} sand content (%) 
taxture (%) (63-20um)} ® Ms es 
A Ü mm nn * 19 m 7 WO 10 20 30 
Pedoganic = 
ormanic carbonate Ictal = Fa(dVFail} 
sontent (%} cantenl (%) iron (g/kg) 
05 OI0482 9 10 3% 9 A 6 * NY 4 9 20 ALS O5 02 
22.164 1.64 
23.29 4 L75 
26,27 + 2.00 
24.67 + 1.99 
28.35 + 2.44 
A3 section lower part 
OSL ages SU 
ka] - 
a schen = 
YOBUM liminalon 
sah 
AXtune (9%) 
12 3. 4 5 8 
PS —— 
{(20-20Cum ! <20um' 
arse Sit conten! (%) 
(63-20um} 
x fine sand (200-63um} 
is: medium Sand (630-ZUyim)} 
8: (0ar88 Sand (2000-630um) 
„sand content (%) 
5 Ne SS 
r 
Ongank: 
ent (6) 
a1 Hann 
Aa Conan 
"Oarse ailt-sized 
rboanala contarnt 
carbonate 
An lent (6) 
HEN = 
ctäl = Fe(dyFe(1) 
fon (darkp+ 
— 
17.50 + 11.927 
95.38 + 9.21 
; dlssalwe 
Wosum Blämanaborn 
% 
PS —— 
M-200ym I Nam) 
6: fine sand [200-63yum} 
MS: mechurm Sad (630-200) 
"8: onarae sand LAKXKHE Cm 
Ola Conan 
Darse silt-alzed 
*achonate eonbant 
Figure 4. (color online) Stratigraphic sequence and analytical data for the A3 section (40°06’38.9”N, W 03°08’47.5”W; 560 m asl), showing 
OSL dating results, sediment units (SU), sampling points, palaeo surfaces (PS), and grain-size parameters (soil texture %, coarse silt content % 
sand content %), organic content, carbonate content (total and coarse silt-sized fractions), and ratio between pedogenic and total iron as a 
weathering index. For legend, see Figure 2. 
paleosol (palaeo surface (PS) 1; Fig. 5C) shows a strong red- 
dish ochre-brown color, bioturbation features, and numerous 
carbonate nodules as well as up to 15-cm-long carbonate con- 
cretions with rhizolith-like shapes. The paleosol (PS-I1) 
exhibits maximum values of magnetic susceptibility and a 
peak in the Fe(d)/Fe(t)-ratio. However, the grain-size patterns 
require closer consideration. Generally, in all sections, —30— 
70% of the silt and sand fraction are comprised of calcium 
carbonate minerals. The clay fraction shows a much lower 
percentage of carbonate, but in line with maximum values 
of the total carbonate content, it rises up to more than 50%, 
showing a sedimentary origin for the clay-sized carbonate 
minerals. Therefore, grain-size patterns appear to be suitable 
for analyzing sedimentation processes, but less suitable for 
detecting pedogenic processes. This can be seen, e.g., in 
the Paraiso section in SU-4, in which clay contents show 
higher values in the parent material as compared to the pale- 
osol (Fig. 6), although it is the most intensely developed pale- 
osol of the whole section. However, if we also consider clay 
contents measured after decalcification of the samples 
(Fig. 9), 37-54% of the clay below the paleosol consists of 
calcium carbonate minerals, while the paleosol itself also 
shows an increase of clay after decalcification. This may be 
due to the disaggregation of clay aggregates during 
Jdecalcification or the release of clay from inside of secondary 
carbonate concretions. Finally, this paleosol shows the high- 
est carbonate-free clay contents in the Paraiso and Villarubia 
sections. 
Middle part of the sections (SU-5 and SU-6) 
In SU-5, the content of coarse silt increases slightly with 
almost no coarse components except for some pebbles in 
Fuentiduena. SU-5 is characterized by bioturbation fea- 
res and secondary carbonate concretions. In Paraiso, a 
paleosol (PS-2; Fig. 5C) developed in the upper part of 
SU-5 showing a dark reddish-brown color and reduced 
carbonate contents (28%; Fig. 6) compared to the loess 
elow (40%). Clay contents again reach values higher 
:han 19%, but the less intense color suggests a lower 
degree of pedogenesis compared to the paleosol below. 
Except for Paraiso, the paleosol (PS-2) is missing in all 
ather sections, pointing to surface erosion before the dep- 
osition of the next loess layer. 
In all sections, SU-6 contains the highest contents of coarse 
silt encountered thus far (>50% in Parafso and Fuentiduena), 
which is likewise expressed by a PSI surpassing 2.5 in Paraiso 
and 2.76 in Fuentiduefa. In all sections. the coarse silt 
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