<sup>18</sup>O analyses of bulk lipids as novel paleoclimate tool in loess research – a pilot study
<p>The analysis of the stable oxygen isotopes <span class="inline-formula"><sup>18</sup>O</span> and <span class="inline-formula"><sup>16</sup>O</span> has revolutionized paleoclimate research since the middle of the last cent...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | deu |
| Published: |
Copernicus Publications
2022-04-01
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| Series: | Eiszeitalter und Gegenwart |
| Online Access: | https://egqsj.copernicus.org/articles/71/83/2022/egqsj-71-83-2022.pdf |
| Summary: | <p>The analysis of the stable oxygen isotopes <span class="inline-formula"><sup>18</sup>O</span> and
<span class="inline-formula"><sup>16</sup>O</span> has revolutionized paleoclimate research since the middle of the
last century. Particularly, <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> of ice cores from Greenland
and Antarctica is used as a paleotemperature proxy, and <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> of deep-sea
sediments is used as a proxy for global ice volume. Important terrestrial
archives to which <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> as a paleoclimate proxy is successfully
applied are speleothems, lake sediments, or tree rings. By contrast, <span class="inline-formula"><i>δ</i><sup>18</sup></span>O applications to loess–paleosol sequences (LPSs) are scarce. Here
we present a first continuous <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> record (<span class="inline-formula"><i>n</i>=50</span>) for the LPS
Crvenka in Serbia, southeastern Europe, spanning the last glacial–interglacial cycle
(since 145 ka). From a methodological point of view, we took
advantage of a recently proposed paleoclimate/paleohydrological proxy based on
bulk <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> analyses of plant-derived lipids. The Crvenka <span class="inline-formula"><i>δ</i><sup>18</sup></span>O<span class="inline-formula"><sub>bulk lipid</sub></span> values range between <span class="inline-formula">−10.2</span> ‰
and <span class="inline-formula">+23.0</span> ‰ and are systematically more positive in
the interglacial and interstadial (paleo-)soils corresponding to marine
oxygen-isotope stage (MIS) 1, 3, and 5, compared to the loess layers (MIS 2,
4, and 6). Our Crvenka <span class="inline-formula"><i>δ</i><sup>18</sup>O</span><span class="inline-formula"><sub>bulk lipid</sub></span> record provides no
evidence for the occurrence of interstadials and stadials comparable to the
Dansgaard–Oeschger events known from the Greenland <span class="inline-formula"><i>δ</i><sup>18</sup>O</span><span class="inline-formula"><sub>ice core</sub></span> records. Concerning the interpretation of our Crvenka <span class="inline-formula"><i>δ</i><sup>18</sup></span>O<span class="inline-formula"><sub>bulk lipid</sub></span> record, plant-derived lipids such as fatty acids
and alcohols are certainly strongly influenced by climatic factors such as
temperature (via <span class="inline-formula"><i>δ</i><sup>18</sup>O</span><span class="inline-formula"><sub>precipitation</sub>)</span> and relative air
humidity (via <span class="inline-formula"><sup>18</sup>O</span> enrichment of leaf water due to evapotranspiration).
However, pool effects in the form of non-water-correlated lipids such as
sterols or the input of root-derived lipids need to be considered, too.
Similarly, the input of soil-microbial lipids and oxygen exchange reactions
represent uncertainties challenging quantitative paleoclimate/paleohydrological
reconstructions based on <span class="inline-formula"><i>δ</i><sup>18</sup>O</span><span class="inline-formula"><sub>bulk lipid</sub></span> analyses from LPSs.</p> |
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| ISSN: | 0424-7116 2199-9090 |