Combining Inorganic and Organic Carbon Stable Isotope Signatures in the Schwalbenberg Loess-Palaeosol-Sequence Near Remagen (Middle Rhine Valley, Germany)

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 (δ 13 C) and contents of the organic-and inorganic C pools. 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 toward 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.

Middle to Late Pleistocene environments based on stable organic carbon and nitrogen isotopes of loess‐palaeosol sequences from the Carpathian Basin

“…Other effects on the water availability, such as permafrost dynamics (Vinnepand et al . 2020), can be ruled out, based on the lack of periglacial features in the loess deposits of the southern Carpathian Basin.…”

Luminescence Sensitivity of Rhine Valley Loess: Indicators of Source Variability?

“…This study focusses on the loess deposits of the Schwalbenberg site, located west of the city of Remagen and just north of the confluence between the rivers Ahr and Rhine, in western Germany (Figure 1). Loess deposits up to 30 m thick provide some of the thickest and most complete deposits in Western Europe [54][55][56]. The loess deposits at the Schwalbenberg site drape the fluvial terraces of the Rhine, and the Devonian sedimentary bedrock at higher altitudes [52,54] (Figure 1).…”

“…Loess deposits up to 30 m thick provide some of the thickest and most complete deposits in Western Europe [54][55][56]. The loess deposits at the Schwalbenberg site drape the fluvial terraces of the Rhine, and the Devonian sedimentary bedrock at higher altitudes [52,54] (Figure 1).…”

“…Most of these investigated and excavated profiles were exposed along the margins of the hillslope, with the antiquity of the deposits inferred through correlation and observation of the c. 24 ka age Eltville Tephra e.g., [57][58][59][60], and a luminescence chronology produced in [55]. More recently, four cores (REM 1, 3A/3B, 5) were drilled and sampled across the hillslope in order to reconstruct palaeoenvironmental change in four dimensions based on physical characteristics and geochemistry [53,54]. In this study, we focus on two sets of samples collected from the Schwalbenberg locality.…”

“…One half of the core was sampled at semi-regular intervals for D e preparation and measure-ment, and the other half was sampled at the same depths for dose rate analysis to facilitate age calculations in the forthcoming work. The stratigraphy of the core was logged and correlated with the adjacent core REM3A to produce a composite core REM3 (described in [53,54]; Figure S1). A total of 102 samples were collected at high frequency (c. 10-50 cm intervals) down core REM3B.…”