Abstract. Archaeological research in high mountain regions has gotten a lot more attention since
the discovery of the copper age mummy called “Ötzi” in the Ötztaler
Alps in 1991. In the Tyrolean Stubai Alps, the Mesolithic site Ullafelsen at
1869 m a.s.l. (above sea level) close to the recent upper timberline in the Fotsch Valley
represents, on the one hand, a very important archaeological reference site
and offers, on the other hand, intriguing research questions related to, amongst
others, pedogenesis. Given that no biomarkers and stable isotopes
have been hitherto investigated, we aimed at contributing with respective analyses and
additional radiocarbon dating to a better understanding of the landscape
evolution and pedogenesis on and around the Ullafelsen. Our results for modern vegetation suggest that leaf-wax-derived n-alkanes
allow us to chemotaxonomically distinguish between subalpine deciduous trees
(nC27 predominance) versus (sub)alpine grasses, herbs and dwarf shrubs
(nC29, nC31 and/or nC33 predominance). Except for Juniperus, conifers
produce no or extremely low n-alkane contents. Although no clear vegetation
changes could be inferred from the n-alkane patterns of the investigated soil
profiles, the total n-alkane content (TAC) was developed for the first time
as an unambiguous proxy for distinguishing between buried (= fossil) topsoils
(2Ahb horizons) and humus-enriched subsoils such as Bh horizons of podzols.
Based on this leaf wax proxy, we can rule out that the 2Ahb?/Bh? horizons
under question on the Ullafelsen are buried topsoils as suggested
previously. Dating of the H2O2-pretreated soil samples yielded
14C ages for the podzol Bh horizons ranging from 6.7 to 5.4 cal kyr BP. This is clearly younger than the overlying Mesolithic living floor (LL)
(10.9 to 9.5 cal kyr BP) but pre-dates the assumed intensification of
alpine pasturing from the Bronze Age onwards. Both the LL and the directly
overlying OAh3 horizon yielded black carbon maxima and benzene
polycarboxylic acid patterns reflecting fire-induced human impact during the
Mesolithic. The discrepancy between the Mesolithic charcoal 14C ages
(ages of ≥ 9.5 cal kyr BP) versus the 14C ages obtained for bulk
n-alkanes ranging from 8.2 to 4.9 cal kyr BP suggests that non-alkane-producing conifers predominated the vegetation on and around the Ullafelsen
after the Mesolithic occupation. Only with the anthropo-zoological lowering
of the timberline associated with alpine pasturing since the Neolithic and
especially the Bronze Age has an n-alkane-producing vegetation cover (grasses,
herbs or dwarf shrubs) started to predominate.