D. Wolf et al.
2010), sample preparation was performed under subdued
red-light conditions (640 + 20 nm), including wet sieving,
removal of carbonates and organic material, and a density
separation using sodium polytungstate. We etched the quartz
separates in 40% HF for 50 minutes.
For OSL measurement, quartz grains were mounted on alu-
minum cups, using a 3-mm mask that restricted the number of
grains to 100-300 grains per disc. Except for samples HUB
470, HUB 471, and HUB 472, which were measured at the
Humboldt University in Berlin, all luminescence measure-
ments were carried out at the University of Bayreuth using
an automated Risg-Reader TL/OSL-DA-15 equipped with a
9J0Y/90Sr ßB-source for artificial irradiation. Blue LEDs
(470 + 30 nm) were used for OSL stimulation, and the lumi-
nescence signal was detected by a Thorn-EMI 9235 photo-
multiplier combined with a 7.5mm U-340 Hoya filter
(290-370 nm).
All luminescence shine-down curves were recorded for 40
seconds at an elevated temperature of 125°C, using a single
aliquot regenerative-dose (SAR) protocol (Murray and
Wintle, 2000), which was enhanced by an additional hot-
bleach step (Murray and Wintle, 2003). Equivalent doses
were determined using the first 0.6 seconds of the OSL signal
after subtracting a background that was derived from the last
7,5 seconds.
Only aliquots with a recycling ratio of 0.9-1.1, a recuper-
ation of < 5% of the natural sensitivity corrected signal inten-
sity (Murray and Wintle, 2000), and an OSL-IR depletion
ratio (Duller, 2003) in the range of 0.9-1.1 were accepted
for equivalent dose calculation. Because dose response
curves of some samples (BT 1368, BT 1372, BT 1374, BT
1376, BT 1383, BT 1384, and HUB 470) suggested that
these samples might be close to their saturation levels, we
would like to emphasize that all ages derived from these sam-
ples may seriously underestimate the true burial age and can
anly be interpreted as minimum ages.
For dose rate (D) determination, the U- and Th-concentrations
were detected by thick source w-counting, and the K-contents
were measured by ICP-OES. Calculations for determining the
2nvironmental dose rate were done applying DRAC v1.2 (Dur-
can et al., 2015) in combination with the conversion factors
given by Guerin et al. (2011). Applying an interstitial water con-
tent of 8 + 3% for samples BT 1375, BT 1381, BT 1383, BT
1384, and BT 1544, a water content of 5+3% was assumed
to be representative for all other samples as derived from
measurements of present-day water contents and considering
both sedimentological properties and differences in the geo-
graphical settings of the locations. Cosmic dose rates were cal-
culated according to Prescott and Hutton (1994) using the
‘calc_CosmicDoseRate’ function provided by the R package
‘Luminescence’ (Kreutzer et al., 2012, 2016; R Development
Core Team. 2016).
Heavy mineral analyses
The separation of heavy minerals was conducted after the pro-
cedure described by Mange and Maurer (1991), including
drying the samples, sieving to a grain-size fraction between
40 um and 400 um, removal of carbonates by adding acetic
acid, eliminating gypsum by repeated soaking and sieving,
and dispersing with Na4,P,O-. Finally, the heavy mineral frac-
jon was separated by using sodium polytungstate. For the
identification of the heavy minerals, we produced strewn
slides after Kurze (1987) for transmitted light microscopy
2y coating with gelatin, and unilateral embedding in the
immersion fluid &-chloronaphtalene with a light refraction
3f 1.633. For optimal analyses, we identified and counted at
least 200 translucent mineral grains. Determination of the
identity of translucent minerals was based on grain morphol-
agies, colors, pleochroism features, fissility, break, light
refraction, double refraction, as well as inclusions (for details,
zee Wolf et al., 2019).
Rock magnetic measurements
Magnetic susceptibility was measured on two different
frequencies (300 and 3000Hz) using the MAGNON
VFSM susceptibility bridge (320 Am”' AC field, sensitivity
greater than 5 x 107° SI) and transferred to mass specific sus-
ceptibility x after determining sample density. The frequency
dependent susceptibility (Xga) was calculated using the differ-
ence of both measured frequencies. The isothermal remanent
magnetisation (IRM) was generated employing a MAGNON
Pulse Magnetiser II with fields of 2000 mT and 200 mT
backfield) and resulting imposed magnetic remanences
were determined using an AGICO JR6-spinner magnetome-
:er. The s-ratio was calculated based on both values (s-ratio =
((IRMb00 m1t/IRMho000 mT) + 12).
Stable isotope analyses
In order to reconstruct paleoclimatic and paleohydrological
changes, we performed compound-specific stable isotope
analyses of 8'°C and &°H on the aliphatic lipid fraction con-
:aining n-alkanes. The 8BC signal of leaf waxes can be used
© distinguish between Cz and C„, vegetation (Rommer-
;kirchen et al., 2006), with Cz plants showing lower values
(—23%o to -34%o) compared to C, plants (-6%o to —-23%o,
Schidlowski, 1987). Additionally, the 8°C value of leaf
wax n-alkanes depends on the 8'°C of the atmospheric
CO», as well as on its concentration, air temperature, relative
numidity, and precipitation during the growing season (e.g.,
Diefendorf et al., 2010). The 8°H values of leaf waxes reflect
‘he isotopic signal of the precipitation, which depends mainly
on the isotopic composition of the moisture source, but is also
influenced by the temperature, amount, continentality, and
altitude effect (Berke et al., 2015; Sachse et al., 2012; Tipple
st al., 2013). Because we assume that S’Hıyax variations in the
ıpper Tagus loess correspond to changes in 5'°O in the North
Atlantic surface waters, thus indicating that the source effect
was one dominant control on S’Hoyax (Schäfer et al., 2018),
here we focus solely on 8'°C as proxy for hydrological
changes.
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