Upper Tagus loess formation and the marine atmosphere off the Iberian margin 
Total lipid extraction and separation into lipid fractions is 
described in Schäfer et al. (2016a). The compound-specific 
carbon isotope measurements were performed on an IsoPrime 
‚00 mass spectrometer, coupled to an Agilent 7890A gas 
chromatograph via a GC5 Pyrolysis/Combustion interface 
that operated in combustion mode (CuO reactor) at 850°C. 
Samples were injected using a split/splitless injector in split- 
liess mode. The GC was equipped with a 30 m fused silica col- 
umn (HP5-MS, 0.32 mm i.d., 0.25 um film thickness). The 
precision was checked by injecting a standard alkane mix 
(C27, Coo, Cz33) with known isotopic composition (Schimmel- 
mann) twice every six runs. The analytical error was gener- 
ally better than 0.5%o (triplicate measurements). The stable 
carbon isotope composition is given in the delta notation 
85°C) versus Vienna Pee Dee Belemnite (V-PDB). For the 
compound-specific hydrogen isotope measurement, the 
GC5 mode was changed to pyrolysis by using a Cr (Chro- 
meHD) reactor at 1000°C. Adjustments for the GC, the stan- 
dard and the injection procedure were the same as for the 
stable carbon isotope measurements. The H3+ correction fac- 
tor was checked every two days and was stable at 3.48 + 0.06. 
The analytical error was generally better than 5%o (three rep- 
licates), and we report only values with a standard deviation 
better than 6%o (for more details, see Schäfer et al., 2018). 
55%, and sandy layers, some with more than 50% of fine 
and medium sand. Among the sandy and clayey layers, 
‘here are very thin, laminar, carbonate accumulations with 
carbonate contents of up to 66% that indicate precipitation 
from carbonate-saturated runoff (Fig. 5A, B). SU-3 lacks 
clear indications of in-situ soil formation. Instead, the high 
soluble salts and clay contents, and high values of magnetic 
zusceptibility (Fig. 2), indicate that SU-3 mainly consists of 
‚elocated loamy soil material that was derived from surface 
erosion of the surrounding evaporate marls. Sedimentation 
features in these footslope positions are tentatively interpreted 
as a mixture of slope processes and fluvial sedimentation pro- 
cesses in a still-active floodplain environment. 
In contrast to the sections at Fuentiduena and Villamanri- 
Jue, loess and loess derivates of the Paraiso (Figs. 5C, 6) 
and Villarubia (Figs. 5D, 6, 7) sections, located 50m and 
33 m above recent river level (Fig. 8), rest directly on Mio- 
cene marls (SU-1). These marls are characterized by soluble 
salt contents between 48 and 78%, and carbonate contents 
between 9 and 29% (Figs. 6, 7). At the beginning of section 
accumulation, these more elevated areas were not influenced 
5y floodplain processes, but rather were affected by erosive 
instead of depositional processes. Accordingly, in the Paraiso 
section, there is no indication of major SU-3 deposition apart 
from a thin layer of relocated marl deposits. 
RESULTS 
Lithofacies and pedostratigraphic patterns of the 
Upper Tagus loess record 
The Upper Tagus loess record can be subdivided into 10 main 
stratigraphic units (SU-1 to SU-10). The basal two units con- 
:ain the underlying substrates: Miocene marls (SU-1) and 
Middle Pleistocene fluvial gravel terraces (SU-2). Unit 
SU-3 is comprised of relocated material at the base of the sec- 
tions, while SU-4 to SU-9 contain loess deposits that were 
formed during the last glacial period. Holocene colluvial 
deposits (SU-10) cover the top of most of sections. All strati- 
graphic columns together with standard analytical results are 
show in Figures 2-7. The Villamanrique section is strongly 
influenced by slope processes and also contains runoff chan- 
nels in its upper part (Fig. SE), indicating active surface 
dynamics during loess deposition. 
Lower part of the sections (SU-2 and SU-3) 
General topographic positions of the described loess sections 
are shown in Figures 1 and 8. The lower parts of the sections 
differ significantly in relation to their respective elevation 
above the recent river level. In the Fuentiduena (Figs. 2, 3), 
A3 (Fig. 4), and Villamanrique (Fig. 5) sections, which are 
elevated between 10-20 m above recent river level, the last 
glacial deposits rest on older fluvial terraces consisting of 
poorly sorted, well-rounded gravels and coarse-grained 
sand lenses (SU-2). The subsequent unit (SU-3) is character- 
ized by a more than 2-m-thick succession of alternating layers 
of dark brown clayey sediments with clay contents of up to 
First indications of loess deposition (SU-4) 
The next unit, SU-4, marks the beginning of the last glacial 
ioess formation in the study area. Sediment samples show 
aigher silt and fine sand contents, while sections located 
closer to the river level show generally higher sand contents 
‘e.g., Fuentiduefa) compared to sections in more elevated 
ositions (Fig. 8). 
These relations are well expressed in form of texture- 
:‚elated indices, such as the grain-size index (GSID) that 
compares coarse silt contents with all finer fractions, thus 
indicating wind strength in loess archives (Rousseau et al., 
2002). In view of the high fine sand contents (e.g., up to 
27% in Fuentiduefa section, Fig. 2), loess deposits appear 
Oo be mainly of local origin (see e.g., Bosq et al. 2018). In 
order to consider the fine sand fraction for calculating a 
wind-strength-related proxy, we applied a new particle-size 
index (PSI=(20-200um)/<20um) which, besides coarse 
silt, also emphasizes fine sand (Calvo et al., 2016; Wolf 
et al., 2019). In the Parafso section, which is (along with 
‘he Villarubia section) the most suitable section for studying 
aeolian transport processes due to its distal position from the 
deflation area, the PSI rises to about 1.5 in SU-4 (Fig. 6), 
which is quite low compared to other loess units. Further sed- 
.mentological characteristics of SU-4 include the highest car- 
2onate contents in all sections (Figs. 2, 6, 7), the highest 
content of medium and coarse sand in Fuentiduena (Fig. 2), 
and a scattered occurrence of angular, several-cm-thick 
stones or pebbles in Paraiso and Fuentiduefa that indicate 
the contribution of slope processes during the formation of 
SU-4. In the upper part of SU-4, a strongly weathered 
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