Abstract
Western Central European Loess-Palaeosol-Sequences (LPS) provide valuable terrestrial records of palaeoenvironmental conditions, which formed in response to variability in the North Atlantic climate systems. Over the last full glacial cycle (~130 ka), climate oscillations within these systems are best documented in deep sea and ice cores; the responses of terrestrial systems are not yet fully understood. A better understanding of metabolism governing input and output variables of organic- and inorganic C pools is, however, crucial for investigating landscape-atmospheric feedback processes and in particularly, for understanding the formation of calcareous LPS as environmental archives. Here we quantify the contributions of primary carbonates (PC) and secondary carbonates (SC) to the overall inorganic carbon pool down a LPS at the Schwalbenberg site, based on the natural abundance ratio of stable carbon isotopes (δ13C). This facilitates detailed insights into the carbonate metabolism and hence, loessification and percolation processes. PC accumulate predominantly in cold phases during periods of reduced biological activity and become leached during wetter and warmer periods contemporary with higher rates of SC re-precipitation and total organic carbon (TOC) increases due to enhanced biomass production. We find that mineral dust input is most significant during stadials, as well as towards the end of warmer interstadials, characterised by gradual cooling back to stadial conditions. Pedogenesis in the Schwalbenberg LPS kept pace with surface accumulation of mineral dust. This indicates that palaeosols are of accretionary nature, which gives raise to the idea of incorporation of former topsoils in preserved subsoil horizons. Our study decodes fundamental aspects of the link between atmospheric dust circulation and terrestrial records in western Central Europe. In addition, interdependencies between factors governing the regional moisture budged and LPS can be reconstructed in a more holistic way than before.
Highlights
Terrestrial carbon pools respond to changes in climate by trapping or releasing carbon to the atmosphere (Adams and Post, 1999; von Lützow and Kögel-Knabner, 2009)
We showed that enhanced water availability for plants indicated by δ13C(TOC) is not necessarily a function of increased precipitation but can be caused by increased sediment moisture due to permafrost dynamics
Direct responses of terrestrial C pools to North Atlantic atmospheric and climate oscillations are likely to be reflected by the total organic carbon (TOC)/primary carbonates (PC) ratio, which is shown by a correlation of the new sediment core REM 3A to the Schwalbenberg II section
Summary
Terrestrial carbon pools respond to changes in climate by trapping or releasing carbon to the atmosphere (Adams and Post, 1999; von Lützow and Kögel-Knabner, 2009). Total organic carbon (TOC) and total inorganic carbon (TIC) records derived from terrestrial archives can be used for correlations with ice core data along with independent age control (Adams and Post, 1999; Hatté et al, 1999) These correlations, pre-require detailed understanding of formation processes of investigated archives against the background of climate and environmental changes affecting terrestrial carbon pools. The quantification of PC and SC, based on the natural abundance ratio of stable carbon isotopes in TIC (δ13C(TIC)), provides a promising tool to gain insight into the role of carbonate metabolism during loess formation and to relate this processes to the palaeoenvironmental conditions prevailing during LPS formation This can inform us about past water percolation in loess and palaeosols (cf Zamanian et al, 2016). We aim to get detailed insights into the carbonate metabolism of the LPS to estimate the degree of loessification and PC input
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