Disentangling Sedimentary Pathways for the Pleniglacial Lower Danube Loess Based on Geochemical Signatures

Stephan Pötter,Yunus Baykal,Philipp Schulte,Daniel Veres,Janina J Nett,Frank Lehmkuhl,Ulrich Hambach

doi:10.3389/feart.2021.600010

Stephan Pötter, Yunus Baykal + Show 5 more

Open Access

https://doi.org/10.3389/feart.2021.600010

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Abstract

The source of aeolian sediments such as loess has been investigated since decades. Reliable knowledge on potential dust sources is crucial to understand past climatic and environmental conditions accompanying the dispersal of early modern humans (EMH) into Europe. Provenance studies are usually performed on small sample sets and most established methods are expensive and time-consuming. Here, we present the results of high-resolution geochemical analyses performed on five loess-palaeosol sequences from the Lower Danube Basin (LDB), a region, despite its importance as a trajectory for EMH, largely underrepresented in loess provenance studies. We compare our results with geochemical data of loess-palaeosol sequences from Austria, Hungary, Serbia, and Ukraine. Based on published literature, we thus evaluate five plausible sedimentary pathways for the LDB loess: 1) the Danube alluvium (DA) pathway, which constrains the transport and re-deposition of detrital material by the Danube and its tributaries; 2) the Carpathian Bending (CB) pathway, where sediment is mainly transported from the Cretaceous to Neogene flysch of the Eastern Carpathian Bending; 3) the Eastern Carpathian (EC) pathway, in which sediment is eroded from the flysch of the Outer Eastern Carpathians, transported by rivers, and deflated by northwesterly to westerly winds; 4) the glaciofluvial (GF) pathway, where dust is deflated from glacial outwash plains in nowadays Ukraine, and 5) the Black Sea (BS) pathway, where dust originates from the exposed shelf of the Black Sea. Based on geochemical data, we consider the DA pathway to be the major sediment trajectory for loess in the LDB. Especially the sequences located close to the Danube and the Dobrogea show similarities to sites in Central and Northeast Hungary as well as Northern Serbia. For the northeastern part of the LDB, we demonstrate that dust input is mainly sourced from primary material from the Eastern Carpathians. Mineralogical estimations and geochemical data render the CB pathway as an additional substantial source of detrital material for the loess of this area. We consider the influence of the GF pathway in the LDB as negligible, whereas some minor influences of the BS pathway cannot be ruled out based on geochemical data.

Highlights

Since the earliest days of loess research, the origin and source of aeolian sediments such as loess have been a matter of debate. Richthofen (1882), a pioneer in loess research, named nonvegetated deserts and desiccated lake beds as potential source areas for loess in China
Our high-resolution geochemical study on several loess-palaeosol sequences from the Lower Danube Basin is among the first multirecord analyses contributing to the understanding
we subdivide the basin into two major domains of loess geochemical signatures

Summary

Introduction

Since the earliest days of loess research, the origin and source of aeolian sediments such as loess have been a matter of debate. Richthofen (1882), a pioneer in loess research, named nonvegetated deserts and desiccated lake beds as potential source areas for loess in China. Since the earliest days of loess research, the origin and source of aeolian sediments such as loess have been a matter of debate. Most studies agree that the formation of dust (i.e., silt-sized particles) essentially involves a series of sedimentary processes prior to aeolian transport and loess formation (Smalley and Smalley, 1983; Pécsi, 1990; Pye, 1995; Muhs and Bettis, 2003; Badura et al, 2013; Sprafke and Obreht, 2016). The knowledge of the sedimentary pathways, the transport chains from the initial production of silt-sized particles to its final deposition and loess formation, is crucial to understand past environmental and climatic systems in varying geographical settings (Muhs, 2018). The reconstruction of atmospheric circulation patterns and climatic gradients is crucial to understand past environmental constraints on the spread of early modern humans (Obreht et al, 2017; Staubwasser et al, 2018), especially in areas which are believed to be important trajectories for their migration into Europe (Anghelinu and Nita, 2014; Chu, 2018; Fitzsimmons et al, 2020)

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