Early Eocene carbon isotope excursions in a lignite-bearing succession at the southern edge of the proto-North Sea (Schöningen, Germany)
<p>Situated at the southern edge of the proto-North Sea, the lower Eocene Schöningen Formation of the Helmstedt Lignite Mining District, Lower Saxony, Germany, is characterized by several lignite seams alternating with estuarine to brackish interbeds. Here, we present carbon isotope data for b...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-10-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/18/2231/2022/cp-18-2231-2022.pdf |
| Summary: | <p>Situated at the southern edge of the proto-North Sea, the
lower Eocene Schöningen Formation of the Helmstedt Lignite Mining
District, Lower Saxony, Germany, is characterized by several lignite seams
alternating with estuarine to brackish interbeds. Here, we present carbon
isotope data for bulk organic matter (<span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span>), total
organic carbon content (%TOC), and palynomorphs from a 98 m thick
sequence of the Schöningen Formation in combination with a new robust
age model, which is based on eustatic sea level changes, biostratigraphy,
and a correlation with existing radiometric ages. Based on the <span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span> data we observe six negative carbon isotope excursions
(CIEs) reflecting massive short-term carbon cycle perturbations. A strong
CIE of <span class="inline-formula">−</span>2.6 ‰ in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span> values in the Main Seam and the succeeding marine interbed can be related to the
Paleocene–Eocene Thermal Maximum (PETM). The subsequent CIE of <span class="inline-formula">−</span>1.7 ‰ in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span> values may be
correlated with the Eocene Thermal Maximum 2 (ETM2) or slightly older events preceding the ETM2. High-amplitude climate fluctuations including at least four minor CIEs with a maximum negative shift of <span class="inline-formula">−</span>1.3 ‰ in
<span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span> in the upper part of the studied section are
characteristic of the Early Eocene Climatic Optimum (EECO). Palynological
analysis across the Main Seam proved that shifts in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span> values are correlated with changes in the peat-forming wetland vegetation, specifically the change from a mixed angiosperm
and gymnosperm flora to angiosperm-dominated vegetation at the onset of
the PETM. The PETM-related CIE shows a distinct rebound to higher <span class="inline-formula"><i>δ</i><sup>13</sup></span>C<span class="inline-formula"><sub>TOC</sub></span> values shortly after the onset of the CIE,
which is recognized here as a common feature of terrestrial and marginal
marine PETM records worldwide and may reflect a stepwise injection of carbon into the atmosphere.</p> |
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| ISSN: | 1814-9324 1814-9332 |