Abstract
Holocene climate in Central Europe was characterized by variations on millennial to decadal time scales. Speleothems provide the opportunity to study such palaeoclimate variability using high temporal resolution proxy records, and offer precise age models by U-series dating. However, the significance of proxy records from an individual speleothem is still a matter of debate, and limited sample availability often hampers the possibility to reproduce proxy records or to resolve spatial climate patterns. Here we present a palaeoclimate record based on four stalagmites from the Hüttenbläserschachthöhle (HBSH), western Germany. Two specimens cover almost the entire Holocene, with a short hiatus in between. A third stalagmite grew between 6.1 ± 0.6 ka and 0.6 ± 0.1 ka and a fourth one covers 11.0 ± 0.4 ka to 8.2 ± 0.2 ka. Trace element and stable isotope data allow to compare coeval stalagmites and to reconstruct potential climate patterns in the Holocene. In addition, Sr isotopes reveal soil processes and recharge of the aquifer. The aim of this study was to evaluate the consistency of the proxy data recorded by the individual stalagmites and to validate the results using a multi-proxy approach. Due to the close proximity of HBSH (<1 km) to the intensively investigated Bunker Cave system, this dataset also provides the unique opportunity to compare this record with a time-series from another cave system in the same climate region. While the initial growth phase at the onset of the Holocene shows similar patterns in both caves, the data show an opposing trend in the past 6 ka, most likely induced by the effect of disequilibrium isotope fractionation, resulting in a strong increase in δ13C and δ18O values. The stable isotope data from Bunker Cave do not show this pattern. Trace element data support the interpretation of the HBSH stable isotope data, highlighting the importance of a multi-proxy approach, and the need to replicate speleothem records both within a cave system and ideally using other caves in the region.
Highlights
Speleothems are well established terrestrial palaeoclimate archives and widely used for the reconstruction of past climate and environmental variability on different time scales (e.g., Genty et al, 2003; Fohlmeister et al, 2012; Moseley et al, 2014; Luetscher et al, 2015; Wassenburg et al, 2016a; Mischel et al, 2017a; Lechleitner et al, 2018; Weber et al, 2018a; Budsky et al, 2019)
For sample HBSH-3, HBSH-4, and HBSH-5, sample amounts of approximately 300 mg were used, and chemical separation of U and Th prior to analysis was performed at the Max Planck Institute for Chemistry (MPIC) and the Institute for Geosciences following the methods described in Hoffmann (2008) and Yang et al (2015)
The growth history of speleothem HBSH4 is similar to HBSH-3 with an initial growth phase during the Bølling-Allerød between 13.6 ± 0.3 ka and 13.2 ± 0.1 ka, followed by a growth stop until 11.4 ± 0.1 ka, representing a growth inception shortly after the onset of the Holocene at 11.7 ± 0.1 ka
Summary
Speleothems are well established terrestrial palaeoclimate archives and widely used for the reconstruction of past climate and environmental variability on different time scales (e.g., Genty et al, 2003; Fohlmeister et al, 2012; Moseley et al, 2014; Luetscher et al, 2015; Wassenburg et al, 2016a; Mischel et al, 2017a; Lechleitner et al, 2018; Weber et al, 2018a; Budsky et al, 2019) One of their key features is the possibility to obtain independent, precise and accurate ages, using the U-series disequilibrium method (Scholz and Hoffmann, 2008; Cheng et al, 2013) and the construction of a robust age-depth model, provided that post-depositional alteration did not affect U-mobilization (Scholz et al, 2014; Bajo et al, 2016). Additional proxies have been established for speleothems, such as Sr isotopes to reconstruct changes in aeolian dust transport, weathering conditions, precipitation amount, and water pathways in the karst aquifer (e.g., Banner et al, 1994, 1996; Li et al, 2005; Hori et al, 2013; Belli et al, 2017; Weber et al, 2017, 2018a)
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