D. Wolf et al.
m
JPPER TAGUS LOESS SECTIONS
Allamanrique section
"QUATIGN
5 7.2993 X + 2.73 10° m kg
? = 0.0954 in = 261
Fr)
Jillarubia section
EQUATIGN
7 65349 X +39% 10
. SAH Di
SF
10% —
=
„OESS-PALAEOSOL SEQUENCE
SEMLAC, ROMANIA Pa
'Zeeden et al, 2076, 2078) Fa
ZQUATION E
= 6,926 - X + 1.595 - 10° m'’ka” Fa
Va
.“
BEAT - AH
5
7
| a”
Fuentidueha section
EQUATION
Y = 6.5832 X + 2.76 - 10° mg)
7' = 0.993 (n = 34]
A 0!
‚AGUS LOESS
EQUATION
Y=T1621-X + 2.53 - 107m'kg‘
1 41 ma wa
IB = 2.8-10* m’kg!
(B = 27-10” m'kg”
MB= 2.7410" m'’kg"
Y- afye=
Parafso section
EQUATION
Ya 7023d-X + 2.74: 10° m'kg”
R'=0.98457n= 54
(B = 1.4-10° m'kı‘
A3 section
ZCUATION
0m 7.8423 X + 1,4 10*m'kg"
Al ı 0,9952 {nr = a5
TG, A
10° Via in m'kg“ 107 10*
Figure 12. Low field susceptibility x300 Hz (in m’kg"') vs. frequency dependent susceptibility (x = %300 Hz - x3000 Hz in m’kg”'). (A)
Samples from the different Iberian loess sections (Villamanrique-light blue; Paraiso-dark blue; A3-green; Fuentiduena-red; Villarubia-yel-
low) follow the same trend showing increasing x300 Hz with increasing Xra, SO-called magnetic enhancement. This magnetic enhancement is
based on climatically controlled weathering processes and formation of magnetic particles. The calculated detrital background susceptibility of
he parent material Xp varies between 1.4 and 3.9 * 107° m’kg”'. (B) All samples from the upper Tagus loess were combined and plotted
against a reference data set from the Semlac loess-paleosol sequence in Romania (Zeeden et al., 2016, 2018). Both data sets show the
same trend of magnetic enhancement; however, the detrital background susceptibility Xp of the Tagus loess is considerably lower than the
values from Romania. (For interpretation of references to color in this figure caption, the reader is referred to the web version of this article.)
t-
LE
(ii) Likewise, the paleosol linked to PS-1 shows high values
at least in the lower part of the unit, although an exclusive in
situ pedogenic enhancement is unlikely because of inherited
high values in the parent material. (iv) A second maximum
of all values is linked to the paleosol of PS-2, which is less
pronounced compared to PS-1 but still clearly indicated.
Higher up, all values decrease and are characterized by
homogeneity. This may indicate loess deposition under
increasingly arıd environmental conditions that hampered
the formation and preservation of ferrimagnetic and super-
paramagnetic particles carrying elevated signals of x and
3-ratio, even during periods of surface stability. Clear indi-
cations of pedogenic magnetic enhancement are also miss-
ing in PS-3. In Fuentiduefa, PS-3 even relates to a
minimum in all magnetic parameters (Fig. 2). This may
be a result of unfavorable climate conditions during the
time of surface exposure or to the dominance of hematite
aver magnetite/maghemite (e.g., Buggle et al., 2014).
PS-4 and PS-5 also show a decline of Yır, Xtra, and the
3-ratio. These well-expressed minima in the s-ratio may indi-
cate a higher relative abundance of high coercive minerals,
such as hematite and goethite, on the total fraction of
remanence-carrying iron minerals. In view of the generally
low proportion of magnetic particles in units SU-6 to
SU-9, a higher hematite content may be demonstrated by
minima in the s-ratio in PS-5, PS-4, and part of PS-3.
This does not mean that hematite content is lower in SU-3
:o SU-5, but that the general content of magnetic particles
is higher, presumably including low coercive minerals
such as magnetite/maghemite. Therefore, we added a
curve showing the IRM,ooo/Xır ratio as an indication of rel-
ative share of hematite (Fig. 9). We assume that the incor-
poration of hematite-bearing dust (see Roettig et al., 2017,
2019) instead of climatically controlled in situ hematite for-
mation may explain the observed stratigraphic trend of the
IRM5000/ Xır -ratio.
Finally, the colluvial deposits in the Paraiso section (SU-10)
again express high values for all parameters, indicating a mag-
netic enhancement during the course of the Holocene.
Vegetation patterns and paleo-hydrological
information from isotopic analyses
n-alkane patterns
The n-alkane patterns from the Paraiso section show partly dis-
putable results. In general, the odd-over-even-predominance
(OEP) as an indicator of degradation processes (e.g., Tipple
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attns'/Aanann cambridoe oraf/carefterms https’ /Z/idal araf10 1017 /alıa 20720 "
