| 1. |
- Baykal, Yunus, et al.
(författare)
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Detrital zircon U–Pb age analysis of last glacial loess sources and proglacial sediment dynamics in the Northern European Plain
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 274
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Tidskriftsartikel (refereegranskat)abstract
- Loess deposits along the northern fringe of the European loess belt potentially record past changes in dust emission from areas proximal to former ice sheets. Recent chronologies from loess deposits across this region generally agree on greatly enhanced dust deposition rates when the Fennoscandian Ice Sheet reached its maximum extent during the late last glacial. However, uncertainties over the material's source and origin limit understanding of the causes of this enhanced dust activity. In particular, loess in southwestern Poland has been attributed to multiple origins, mainly involving glaciofluvial outwash plains along the Fennoscandian Ice Sheet margin and/or local sources in the mountainous areas of the Sudetes and Western Carpathians. Here we apply detrital zircon U–Pb age analyses for a large number of grains recovered from four loess samples taken from different stratigraphic units exposed at Biały Kościół in southwestern Poland, previously luminescence dated to MIS 4–2, to assess loess provenance as well as its temporal evolution during last glacial Fennoscandian Ice Sheet fluctuations. Furthermore, we analysed the detrital zircon U–Pb age spectra of five samples from potential source sediments to constrain the history of sediment recycling and mixing within the Northern European Plain prior to deflation and loess deposition. The broad range of zircon age components detected in the four loess samples suggests both Fennoscandian and closer Peri-Gondwanan proto-sources while a narrow, dominant Carboniferous age peak is consistent with sourcing from the local Strzelin Hills in the Sudetic foreland. However, the presence of both Fennoscandian and Peri-Gondwanan derived grains in samples from potential source sediments reveals that this mixture of sediment sources is widespread across the Northern European Plain, as a result of long-term glacial and fluvial reworking of cover sediments in the proglacial area throughout the Quaternary. Local rivers draining the Sudetic foreland transported this Fennoscandian-Peri-Gondwanan sediment mixture along with particles denuded from the Strzelin Hills, resulting in a nearby, temporally stable dust source for the Biały Kościół loess during MIS 4–2, while dust emission rates were substantially increased during the last glacial maximum. Given that our model for loess formation at Biały Kościół essentially involves sediment distribution via rivers prior to short distance aeolian transport, we infer that the proportion of northern ice sheet derived particles in European loess deposits is mainly controlled by the drainage pattern of major rivers in relation to Pleistocene ice margins where glaciofluvial sediment is abundant. Based on the presence of Fennoscandian derived zircon grains in European loess deposits, we constrain a southern limit of the influence of northern ice sheet dust sources along the central European highlands that currently divide drainage between the Northern European Plain and the Danube Basins.
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| 2. |
- Bradák, Balázs, et al.
(författare)
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Magnetic susceptibility in the European Loess Belt : New and existing models of magnetic enhancement in loess
- 2021
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 569
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic susceptibility measurements play a key role in Quaternary studies. Magnetic proxies, such as low field and frequency-dependent magnetic susceptibility, are widely applied in the reconstruction of terrestrial paleoclimate, e.g., in the study of loess-paleosol successions. In general, the interpretation of loess magnetic susceptibility signals is based on two commonly accepted models: the pedogenic magnetic enhancement and wind-vigour models. However, there are an increasing number of cases where such models cannot be used. These cases show unusual relationships between the two common loess magnetic susceptibility proxies: low field and frequency-dependent magnetic susceptibility. Such relationships have been attributed to various phenomena including the dissolution of fine-grain minerals and the formation of ultrafine magnetic rims on the surface of coarser grains by weathering. Despite the growing number of these exceptional cases of magnetic enhancement, our knowledge about the occurrence and potential causes of the unusual behaviour of magnetic susceptibility parameters is still limited. This, in turn, hinders the wider application of magnetic susceptibility parameters in loess. To fill this knowledge gap, magnetic susceptibility data of various profiles from the European Loess Belt were collected and compared to reveal various enhancement trends in loess. Along with the analysis of magnetic susceptibility parameters, combined scanning electron microscopy (SEM) and rock magnetic analyses were applied to samples from the Paks loess sequence in Hungary to describe some of the irregular cases, notably the cause of increasing frequency-dependent susceptibility in non-altered sediments. Analysis of loess, paleosol and common mineral samples separated from loess (e.g., muscovite) revealed that various features may be responsible for these increasing frequency-dependent susceptibility values: i) surface weathering (maghemitization) of coarser detrital grains, ii) nanofragmentation by physical weathering and iii) the appearance of significant amounts of ultrafine magnetic inclusions in micas. These special modes of magnetic enhancement of loess do not undermine the importance of the basic theories suggested above, but rather provide three mechanisms that account for some of the increasing number of unusual cases. To aid in the wider and more accurate use of magnetic susceptibility parameters in loess, we review the current magnetic enhancement models with special emphasis on the identification of unusual trends in magnetic enhancement and understanding their drivers.
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| 3. |
- Hällberg, Lars Petter, et al.
(författare)
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Magnetic susceptibility parameters as proxies for desert sediment provenance
- 2020
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Ingår i: Aeolian Research. - : Elsevier BV. - 1875-9637 .- 2212-1684. ; 46
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic susceptibility in sediments has been thoroughly studied as a paleoenvironmental proxy over the last decades. However, it is unknown to what extent magnetic susceptibility variation is also a diagnostic of different sediment sources. Here we investigate if multiple magnetic susceptibility-based parameters can effectively be used as sediment source indicators. New magnetic property data from the Mu Us and Tengger Deserts in China are compared to previously known sediment provenance based on other well-established proxies. To assess the magnetic properties of these deserts, magnetic susceptibility and its out-of-phase component, its dependence on frequency, temperature and low-field amplitude are analyzed. Our results indicate similar sources for the western Mu Us Desert and the Tengger Desert and a distinct source for the eastern Mu Us, in-line with previously hypothesized provenance patterns. However, magnetic properties within the Tengger Desert sediments are homogenous, which may suggest a uniform provenance for the entire Tengger Desert, that the sediments are greatly reworked, or similar magnetic properties in potential multiple source regions. Magnetite is the major magnetic mineral in the study area and the dominant causes for divergence in magnetic properties are the magnetic mineral concentration and domain state. The results here, in particular from the Mu Us, suggest considerable promise for using magnetic susceptibility parameters in desert sediment provenance research.
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| 4. |
- Költringer, Chiara Amalia
(författare)
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Past environment and sediment dynamics in the Black Sea-Caspian Sea region from Southern Russian loess sequences
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Loess deposits are excellent past climate and environment archives and contain records of aeolian mineral dust accumulation. Loess deposits stretch across Eurasia and sequences along the Lower Volga in the Northern Caspian lowland in the South East European Plain represent a key link between European and Asian loess. They were deposited during phases of Caspian Sea sea-level low stands in the Late Quaternary and are confined by deposits of marine sediments from transgressive phases. These sea-level fluctuations of the Caspian Sea and their driving factors are not well resolved, and one obstacle is the lack of palaeoclimate information during phases of sea-level low stands. In contrast to the marine sediments, the continental deposits are understudied and the origin and formation of the material is debated. As a consequence, loess along the Lower Volga is often left out from palaeoclimate reconstructions in the region. This thesis aims to resolve the origin, formation and post-depositional modification of this loess and determines its aeolian origin. Provenance analyses show that Lower Volga loess particles were formed due to glacial grinding and were transported over long distances via rivers prior to near-source aeolian deposition, where the loess experienced phases of pedogenic and cryogenic reworking. While no temporal changes in material supply can be identified for Lower Volga loess, a remarkable spatial variability is seen in dust sources over the wider East European Plain and in the South Caspian Sea region. This variability is linked to material input from multiple local sources, while the larger material supply to the region has broadly similar provenance and derives mainly from areas of continental and mountain glaciation, transported via rivers prior to aeolian deflation. This thesis explores the potential of Lower Volga loess for palaeoclimate reconstructions in Eurasia, and shows a generally cold and arid climate in the Northern Caspian lowland during the Late Quaternary Caspian Sea regression, with strong dusty winds, punctuated by slightly more humid and/or warmer periods. The thesis shows that enviromagnetic methods are suitable for palaeoclimate reconstructions from such cold climate loess, as long as several methods are applied in combination and interpreted appropriately. It also provides information about the magnetic fabric of Lower Volga loess. The findings of this thesis in broader implication show that the Caspian Sea level is only secondarily influenced by local-regional climate variation and that Quaternary Northern Hemisphere glaciation is the primary controller via river discharge to the Caspian Sea.
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| 5. |
- Költringer, Chiara, et al.
(författare)
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Enviromagnetic study of Late Quaternary environmental evolution in Lower Volga loess sequences, Russia
- 2021
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Ingår i: Quaternary Research. - : Cambridge University Press. - 0033-5894 .- 1096-0287. ; 103, s. 49-73
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Tidskriftsartikel (refereegranskat)abstract
- The late Quaternary development of the Lower Volga region of Russia is characterized by an alternating influence of marine and continental environments resulting from fluctuations in Caspian Sea level during the last glaciation. However, sediments deposited under continental conditions have received very little research attention compared to the under- and overlying marine deposits, such that even their origin is still in debate. Detailed magnetic mineralogical analyses presented here show clear similarities to loess. The results suggest that climate during the time of loess deposition, the Atelian regression (27-80 ka, MIS 4-3), was dry and cool, similar to the modern-day Northern Caspian lowland. The magnetic properties recorded in the loess-paleosol sequences of the Lower Volga also point to short episodes of potentially more humid and warmer climate during the late Atelian. The new findings in regard to the local Caspian climate and environmental evolution support decreased river discharge from the Russian Plain and Siberian Plain as the dominant factor causing the low Caspian sea level stand during the Atelian, although local-regional climate changes might have had an additional influence.
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| 6. |
- Költringer, Chiara, et al.
(författare)
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Palaeoenvironmental implications from Lower Volga loess - Joint magnetic fabric and multi-proxy analyses
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 267, s. 107057-
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic fabric (MF) investigations complemented by geochemical and grain surface analyses of the understudied and controversial marine isotope stage (MIS) 5 b, 4 and 3 loess deposits in the Lower Volga region, Russia show that the material has been transported and deposited by wind and to a large extent experienced post-depositional reworking. Grain surface features suggest that the material was glacially ground and fluvially transported prior to final aeolian deposition as loess. Secondary magnetic fabrics in the loess reveal pedogenic and cryogenic processes and a generally cold environment with brief shifts to warmer climate during late MIS 5 and MIS 3. Palaeowind reconstructions derived from preserved primary aeolian MF, indicate locally influenced westerly and north-westerly flow as part of a wider scale westerly wind pattern, similar to modern day winter conditions. We suggest that the climate of the last glacial in the Northern Caspian Lowland was cold and dry, with higher windspeeds and less variability during MIS 4 compared to MIS 3.
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| 8. |
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| 9. |
- Költringer, Chiara, et al.
(författare)
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Quaternary sediment sources and loess transport pathways in the Black Sea - Caspian Sea region identified by detrital zircon U-Pb geochronology
- 2022
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Ingår i: Global and Planetary Change. - : Elsevier. - 0921-8181 .- 1872-6364. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- Constraining the controls on the distribution of sediment at a continental scale is a critical step in understandinglong-term landscape and climate evolution. In particular, understanding of the role of rivers in wider sedimentrouting and impacts on aeolian loess formation on a continental scale remains limited. Extensive Quaternaryloess deposits are present on the East European Plain and in the Black Sea - Caspian Sea region and are associatedwith major rivers draining numerous surrounding cratonic and orogenic hinterland areas. Coupled with this,complex changes in local and global sea level have affected the extent and drainage of the Caspian Sea and theBlack Sea, and Quaternary glaciations have impinged on the northern margin of the East European Plain. Thissuggests that sediment routing and loess formation may show complex patterns and controls. Here, we applyU–Pb dating of detrital zircons from fluvial, marine and aeolian (dominantly loess) sedimentary records on theEast European Plain and in the Black Sea - Caspian Sea region. This shows a strong control of large rivers on thedistribution of sediments at a continental scale in the region, through long-distance transport of several 1000 km,sourced from continental and mountain glacier areas prior to marine or atmospheric reworking and trans-portation. Strong spatial variability in zircon U–Pb data from loess deposits on the East European Plain revealsmultiple diverse sources to the different individual loess sections, whereas no significant temporal variability inloess source is detected during the Late Pleistocene of the Lower Volga loess in South Russia. While the sedimentsupply from glacial areas via rivers plays an important role for the provenance of East European Plain loessdeposits, our data indicate that the stark spatial diversity in loess provenance on the East European Plain is oftendriven by the input of multiple local sources. Similar to the loess, marine sediments from different basins of theBlack Sea and the Caspian Sea also show significant spatial variability. This variability is controlled by the ba-thymetry of the seas, leading to sedimentary intermixing by sea currents within, but not between differentseparated sea basins. A direct comparison of marine and aeolian sediments at the same depositional site suggeststhat although loess and marine sediments are both dominantly sourced from river sediments containing fartravelled sedimentary material, local sources play a more important role in many loess deposits.
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| 10. |
- Volvakh, N. E., et al.
(författare)
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First high-resolution luminescence dating of loess in Western Siberia
- 2022
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Ingår i: Quaternary Geochronology. - : Elsevier. - 1871-1014 .- 1878-0350. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- The south of Western Siberia is an important part of the Eurasian loess belt, containing an extensive record of Quaternary landscape and climate evolution in up to 100 m thick loess deposits with as many as 10 pedocomplexes. However, this important Quaternary archive lacks a reliable absolute chronology, and this has prevented the linking of the widely accepted regional chronostratigraphic correlations with those of other parts of the Eurasian loess belt. Here we present the first results of detailed luminescence dating of the Late Pleistocene loess-palaeosol sequence at the Western Siberian stratotype section of Lozhok. According to the classical regional chronostratigraphic scheme, this sequence records the main stages of the environmental evolution of the region, including three palaeosols correlated with the warming stages of MIS 5e, MIS 5c and MIS 3. Our absolute chronology is based on 38 new luminescence ages (OSL, IR50, pIRIR290). Good agreement between the OSL and pIRIR290 ages suggests sufficient bleaching before deposition. The resulting chronology reveals that, rather than being only Upper Pleistocene in age, the loess-palaeosol sequence at Lozhok actually formed in the Middle and Upper Pleistocene. The ages of individual horizons do not correspond to the previously accepted stratigraphic units and morphological features of pedocomplexes. Our Bayesian chronological model reveals remarkable variation in dust accumulation and preservation at the site. The new results unambiguously identify the presence of an erosional boundary with a hiatus lasting ∼90 ka. The upper pedocomplex, immediately below this discontinuity, formed in sediment deposited between 131 ± 9 ka and 122 ± 11 ka and clearly corresponds to MIS 5. The lower pedocomplex is found in sediment deposited between 240 ± 12 and 199 ± 9 ka, and correlates closely with MIS 7. These new findings demonstrate the urgent need for a wider programme to date the main stratotypes of loess-palaeosol sections in Western Siberia. Only then can the global implications of the regional climate record in this important continental-scale archive be correctly interpreted.
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