Loess Units Research Articles

Assessing phytolith preservation in a Late Quaternary loess-paleosol sequence from the Kashmir Valley, Northwest Himalaya, India

Phytolith content and its preservation in soils form a robust tool for paleoecological reconstruction. Post-depositional processes, however, influence the preservation of phytolith assemblages in soils thus making the paleoecological inferences biased. Here we evaluated the preservation of phytoliths in a Late Quaternary loess-paleosol sequence (LPS) from Kashmir Valley, northwest Himalaya. The soil micromorphological study, physicochemical parameters, phytolith morphometry, and phytolith translocation rates were employed to assess phytolith preservation and absence (not recorded) in the various litho-units of the Wanihama LPS. The comparison of phytolith content and soil physio-chemical parameters including pH, electrical conductivity, available N, P, K, organic carbon, extractable Fe, Zn, Mn and Cu do not show any significant correlation. This suggests that soil physicochemical parameters have a minor role in regulating the preservation of phytoliths in the LPS. The depth distribution of phytoliths exhibits an inconsistent pattern and phytolith content doesn't decrease systematically with depth. The phytolith content usually follows the loess-paleosol stratigraphy, with low concentrations in loess units and high concentrations in paleosols indicating that phytolith assemblages in the LPS have not been altered or translocated as a result of pedogenic processes. The micromorphological observations suggest weak pedogenesis and the sequence does not seem to be significantly mixed by bioturbation activities. This is augmented by the low translocation rate of <18%, and phytolith morphometry suggesting well-preserved phytoliths with minimum morphological alterations along the depth. The absence of phytoliths at certain stratigraphic units in the LPS thus suggests that climatic conditions rather than physicochemical parameters determine the phytolith preservation and their content in the Kashmir LPS.

Grain-size and geochemical investigations on the Novyi Tik site (NW Ukraine) and their significance for understanding the local sedimentary environment in the Pleistocene

&#x0D; &#x0D; &#x0D; Grain size and geochemical composition of the loess-palaeosol sequences are important evidence of the sedimentary environment in the Pleistocene, which enables to revela- tion of the sedimentation rates, the origin of deposits, and the sources of material that contributed to the loess accumulation and pedogenesis. The Kd index (10-50 μm / &lt;5 μm), and the Ti/Zr, Ti/Nb and Ce/Y ratios considered to be indicators of aeolian silt accumulation, whereas the ratio of physical sand to physical clay have been suggested to reveal the relationship between sedimentation and pedogenesis. The grain size and geochemical analysis were applied at the Novyi Tik section (Volyn’ Upland), which is characterized by detailed stratigraphy and lateral diversity of palaeosols and deposits. Based on grain size and geochemical data from the section, four main units have been distinguished, which represent periods with similar sedimentary environment such as MIS 10-7, MIS 6, MIS 5 and MIS 4-2. During MIS 9 and 7, pedogenesis pre- vailed with a slight sedimentary contribution; during short-term cooling, thin loess beds were formed. High loess accumulation rates occurred during MIS 6, however, the source of aeolian dust material was different from those to other loess units. At the end of MIS 6, a period of dynamic sedimentation began, which resulted in the sandy grain-size composition of soils and non-soil deposits of MIS 5. The highest sedimentation rates presumably occurred during the stadials, therefore the soils could inherit the grain-size composition of the parent material. Moreover, during MIS 5 in the valley of the Styr River, episodes of aeolian sand accumulation could take place, since the sandy grain-size composition of soils of that time is widespread throughout the basin of the modern Khrinnyky reservoir. At the end of MIS 5, abrupt changes occurred in the sedimentary environment: sand sedimentation almost ceased and a period of aeolian silt accumulation began, and proceeded until the Holocene.&#x0D; &#x0D; &#x0D;

Periodic variations of alpine glaciation and desertification of the NE Tibetan Plateau: Evidence from the loess-paleosol sequences in the Menyuan Basin

The NE Tibetan Plateau (NETP) is one of the most ecologically vulnerable areas, with large expansion and retreat of desert area since the Last Glacial Maximum. However, the long-term history of desertification in this area and its mechanisms are still unknown due to lack of long-term and well-dated records. Here we present the results of sand particle content (a proxy of local materials) and detrital-zircon ages from a high-resolved loess-paleosol section spanning the past 420 ka in the Menyuan (MY) Basin lying in the NETP. Our results show that the provenance of loess units (formed in glacial periods) was strongly influenced by local desertified materials that were mainly produced by alpine glaciers surrounding the basin, which was significantly different from the paleosol units (formed in interglacial periods). The strong signals of ~100 kyr and ~ 20 kyr cycles in the content of local materials suggest that the desertification of the MY Basin was controlled by both the late Quaternary ~100-kyr ice age and the ~20-kyr precession cycles, which is obviously different from the periodicities of the classic Luochuan loess section in the mainland of the Chinese Loess Plateau (CLP). The strong ~20-kyr cycle in the MY Basin suggest that the alpine glaciation activities in the NETP were driven by local summer insolation. These results allow us to characterize the long-term natural variability of desertification in the NETP, as well as the mechanisms for the spatial and glacial-interglacial variations of loess provenance on the CLP.

Reconstructed Malacothermometer July Paleotemperatures from the Last Nine Glacials over the South-Eastern Carpathian Basin (Serbia)

In this study, the compiled malacological record of the two most important loess–palaeosol sequences (LPS) in Serbia was used to reconstruct the Malacothermometer July Paleotemperature (MTJP) of the last nine glacials. The sieved loess samples yielded shells of 11 terrestrial gastropod species that were used to estimate the MTJP. Veliki Surduk (covering the last three glacial cycles) and Stari Slankamen (covering the last fourth to ninth glacial cycle) LPSs previously lacked the malacological investigations. After the sieving, a total of 66,871 shells were found, from which 48,459 shells were used for the estimation of the MTJP. Through the studied period, the reconstructed MTJP was ranging from 14.4 °C to 21.5 °C. The lowest temperature was recorded during the formation of the loess unit L5, equivalent to the Marine Isotope Stage (MIS) 12. The second-coldest summers were occurring during the MIS 16 glacial. Although the warmest glacial was L8 (MIS 20) according to MTJP, these July temperatures might be overestimated due to only two samples from the poorly preserved L8 unit. The malacological material derived from the loess units at Veliki Surduk and Stari Slankamen LPSs showed great potential for July temperature reconstruction, as the comparison with other regional records showed similar climate changes. Further work is necessary to validate the age scale of the oldest samples, and a higher resolution sampling could lead to more detailed July temperature fluctuations, as was shown for the youngest glacial in this study. Likewise, estimating the July temperature using different proxies (e.g., pollen) from the same LPSs could be used to confirm the observed climate trends.

10Be Indicator for the Matuyama‐Gauss Magnetic Polarity Reversal From Chinese Loess

AbstractThe Matuyama‐Gauss (M‐G) magnetic polarity reversal is regarded as a fundamental time marker in the stratigraphic division of the Quaternary‐Neogene. However, previous paleomagnetic studies have shown that the M‐G is mainly recorded in the Chinese loess unit L33—a glacial stage (corresponding to marine isotope stage 104, i.e., MIS 104)—which is asynchronous with the timing recorded in marine sediments. Here, we solve this long‐standing debate by exploiting a method to extract reproducible records of paleomagnetic field intensity from Xifeng and Lantian loess profiles with meteoric 10Be. The results showed that for both loess profiles, the 10Be‐derived M‐G boundary is located in paleosol S32 ca. 2,589 ± 3 ka, which corresponds to MIS 103. This is synchronous with that seen in marine sediments, though it is, on average, ∼19 ka younger than the boundary inferred from paleomagnetic measurements from the two profiles, which demonstrates that magnetic overprinting has occurred.

Geophysical sediment properties of a late Pleistocene loess–paleosol sequence, Chenarli, northeastern Iran

AbstractWe present stratigraphic, magnetic, diffuse reflectance spectrophotometric analyses, and chronologic data for the Chenarli loess–paleosol sequence in northeastern Iran. Eight loess units (LU) are identified, described, and constrained in time based on relative stratigraphy and luminescence dating from &gt;130 ± 9.1 ka to ~9.8 ± 0.7 ka. Our data indicate that pedogenic magnetite/maghemite formation gives rise to magnetic enhancement in modern soil and paleosols. The top of LU 7 is demarcated by the well-developed last interglacial soil in which magnetic depletion occurred. We infer that magnetic depletion in this paleosol was produced by reducing conditions in a seasonally waterlogged soil during a warm and wet phase within Marine Isotope Stage (MIS) 5e. Units LU 6 to 1 record several episodes of dust accumulation and soil formation during the last glacial and Holocene. Increased dust accumulation rates occurred during middle-late MIS 3 and lasted into the late MIS 2, with a peak during the last glacial maximum (LU 2). These findings could be applicable to understanding magnetic enhancement/dissolution mechanism in the loess–paleosol sequences in study area. We infer paleoenvironmental changes in northeastern Iran relative to northern Iran, Eurasia, and China.

Tectonic Forcing of the Extreme Aridification of the East Asian Interior at Around 900 ka–Insights From the Spatially Inconsistent Magnetization of Chinese Loess

AbstractThe upper sandy loess unit L9 on the Chinese Loess Plateau (CLP) corresponds to marine isotope stages 22–24, and it represents aeolian deposition under conditions of extreme aridification. However, the forcing mechanism remains controversial. Numerous paleomagnetic studies in the eastern CLP show that the coarsest part of L9 is remagnetized and has a normal geomagnetic polarity. However, our results show that in loess sections in the western CLP the coarsest part of L9 records a primary reverse polarity. This spatially inconsistent magnetization pattern originates mainly from the different magnetic carriers of the characteristic remanent magnetization (hematite in the western CLP and magnetite in the eastern CLP), which suggests a different dust provenance between the western and eastern CLP. We ascribe this spatial contrast in dust provenance to the episodic uplift of the northeastern Tibetan Plateau, which also led to the extreme aridification of the East Asian interior at ∼900 ka.

Paleoenvironmental changes in the Brazilian Pampa based on carbon and oxygen stable isotope analysis of Pleistocene camelid tooth enamel

ABSTRACTHere we present paleoenvironmental and paleoclimatic reconstructions of the Brazilian Pampa based on stable isotopes (δ13C, δ18O) in tooth enamel of the Pleistocene camelidsLama guanicoeandHemiauchenia paradoxafrom the Chuy Creek fossil assemblage, including oneH. paradoxafrom a stratigraphic level within a loess unit deposited during the Last Glacial Maximum (26.5–19 ka b2k). The δ13C results show that both species fed mostly on C3 plants, although the mixed diets ofL. guanicoeincluded ~30% C4 or CAM plants.H.paradoxahad C3 diets with &lt;10% C4 or CAM plants. Both species exhibit higher δ18O and aridity indexes compared to other mammals from the assemblage, consistent with ingestion of18O‐enriched water from plants growing in arid/semi‐arid conditions. A comparison with δ13C of camelids from Argentina indicates the camelids from Chuy Creek fed on vegetation similar to that of Dry Pampa, Monte and Patagonic xerophytic steppes. Aridification and expansion of dry steppes in southern Brazil suggest a climate‐driven northeastwards shift of the Arid Diagonal of South America that may have contributed to local extinction of the Pleistocene megafauna. These Lateglacial environmental changes are reflected in the characteristics of the plant and mammalian assemblages of the modern Brazilian Pampa.

Chronostratigraphy of the Periglacial Loess-Paleosol Sequence in Zaprężyn, SW Poland

Abstract Loess-paleosol sequences (LPS) are an exceptional source of palaeoclimate data constituting an indirect record of changing environmental and climatic conditions that prevailed during loess deposition and early diagenesis. The Zaprężyn LPS (17°11′52″E, 51°14′44″N) is situated in the southern morphological edge of the Trzebnica Hills. This sequence provides an opportunity to reconstruct past climate conditions in this part of SW Poland. In this work, we used two sets of optically stimulated luminescence (OSL) dating from the Gliwice and Bayreuth laboratory to establish a chronological framework for this profile. The results of 14C accelerator mass spectrometry (AMS) dating were also used. The dating results are accompanied by detailed analyses of grain-size distribution and colour. The applied methodology allowed us to distinguish four litho-pedotratigraphic units: modern soil S0, L1LL1 loess unit, L1LL2 loess unit and fossil S1 soil. The OSL dating results indicate an unconformity representing a time interval &gt;30 ka between the L1LL1 and L1LL2 units. This unconformity explains the lack of a L1SS1 soil unit. In Zaprężyn LPS, the presence of the ice wedge pseudomorph in L1LL2 loess unit was recorded. Ice wedge pseudomorph approves the presens the permafrost conditions during the Lower Plenivistulian in Trzebnica Hills.

A detailed luminescence chronology of the Lower Volga loess-palaeosol sequence at Leninsk

We present a detailed luminescence chronology of the loess-palaeosol sequences in the Lower Volga region of Russia at the Leninsk site – an important palaeogeographic archive describing the climate and environmental conditions of regressive stages of the Caspian Sea. The chronology of these sediments has received very little attention compared to the under- and overlying marine deposits. The degree of bleaching was addressed by making use of the differential resetting rates of quartz and feldspar. Our results show that the quartz OSL and feldspar pIRIR 50,290 signals were sufficiently bleached before deposition and uncertainties in bleaching have a negligible impact on the reliability of the luminescence ages. The combined quartz OSL and K-feldspar pIRIR 50,290 chronology constrains the main stages of the Northern Caspian Lowland evolution during the Late Quaternary. During early MIS 5 (130–120 ka), the northern part of the Lower Volga was covered by a shallow brackish water estuary of the warm Late Khazarian Caspian Sea transgression. After ∼122 ka, the Volga incised the Northern Caspian Lowland surface following sea-level decrease and the start of subaerial conditions at Leninsk. Loess accumulation rate increased towards the end of MIS 5 and two palaeosols of presumably MIS 5с and MIS 5a age formed, exhibiting features evidencing a dry, cold climate, influenced by long seasonal flooding by the Volga River. Cryogenesis affecting the MIS 5a soil is a regional phenomenon and is dated to between ∼70 and 90 ka. The overlying thick Atelian loess unit formed during the cold periods of MIS 4 and MIS 3. Clear erosional features at the top of the Atelian loess are constrained by luminescence to ∼35 to ∼24 ka, allowing reconstruction of erosion of 150–200 cm of loess.

Comparative analysis of the magnetism between Chinese and Serbian loess deposits

In this study, a systematic comparison of the magnetic properties of the Xifeng loess in northern China and the Titel loess in northern Serbia was conducted. This comparison was performed to identify the causes of the different ranges of magnetic susceptibility (χlf) enhancements from loess units to paleosol units between the two regions. Ultimately, four differences in the contents and domain states of the magnetic minerals were detected. First, the different concentration of magnetic minerals, especially fine-grained ferrimagnetic minerals between the Xifeng and Titel paleosols is the leading cause. Although the factor of pedogenesis dominated the variations in magnetic properties for each of the loess profiles, the different degrees of pedogenesis between them seemingly cannot fully explain the different contents in magnetic minerals. We consider the difference in source distances of aeolian dust or the related factors played a significant role in the contents of the included magnetic minerals. Second, the lower content of thermally unstable maghemite in the Titel paleosols is an important cause of the lower χlf. This difference can be attributed to the varying levels of effective moisture during the pedogenesis periods, which were caused by the precipitation-evaporation difference. Third, the higher content of single-domain particles in Titel paleosols is one of the causes of the lower χlf. This is an attractive point for promoting our understanding of the pedogenic mechanism under different geographical and climatic backgrounds; however, its origin remains unclear. Finally, the higher proportion of antiferromagnetic hematite/goethite in the Titel paleosols is an element that causes the lower χlf, despite its weak effect. Different water and heat conditions during pedogenesis may be responsible for this difference, and the possibility of the influence of the contemporaneous Mediterranean-like climate in the Pannonian Basin should not be excluded.

Quartz luminescence sensitivity variation in the Chinese loess deposits: the potential role of wildfires

AbstractThe sensitivity of optically stimulated luminescence (OSL) of quartz grains has been applied to trace the provenances of sediments in various environments. Here, we studied the OSL sensitivity of quartz grains in four sections (Jingyuan, Huanxian, Xifeng and Luochuan) along a west–east transect on the Chinese Loess Plateau (CLP). The quartz OSL sensitivity in the palaeosol units is higher overall than that in the loess units, and it shows an increasing trend from the west CLP to the east CLP. In palaeosol units, it increases by a factor of ~20 along the west–east transect; while in loess units it increases by a smaller degree of 3–5. The change of provenances and the change of distances between the provenances and the loess sections cannot fully account for the large degree of sensitivity variation between the loess and palaeosol units in the central and eastern CLP. We propose that wildfires may have played an important role in enhancing the quartz OSL sensitivity in the palaeosol units in the central and eastern CLP. Quartz OSL sensitivity has the potential to be used as a proxy for palaeowildfires.

A detailed magnetic record of Pleistocene climate and distal ash dispersal during the last 800 kyrs - The Suhia Kladenetz quarry loess-paleosol sequence near Pleven (Bulgaria)

Loess-paleosol sequences (LPS) from the Lower Danube area are valuable terrestrial archives of environmental change in SE Europe during the Pleistocene. A twenty-seven meters thick sequence has been sampled in Central North Bulgaria near the city of Pleven within the Suhia Kladenetz (SK) quarry. The sedimentary sequence consists of seven loess units and six interbedded paleosol complexes covering the last 800 kyrs. The continuous 2 cm resolution sampling depth interval enabled the recovery of several cryptotephras in addition to a ~ 20 cm thick tephra deposit observed in the field within the L2 loess unit. All cryptotephras are clearly identified in laboratory analyses by their strong magnetic signal, particularly well expressed by concentration – dependent anhysteretic susceptibility (χARM), isothermal remanence (IRM), low field magnetic susceptibility (χlf) and in some cases by frequency dependent magnetic susceptibility (Δχ), coercivity of remanence (BCR), and hard isothermal remanence (HIRM2.0–0.3T). Complementary optical and scanning electron microscope analyses of single grains from the tephra deposit and cryptotephra intervals reveal the presence of volcanogenic grains with smooth glassy surfaces and vesicular internal structure; fluidal grains with bulbous surfaces and dense irregular grains. Grain size sensitive magnetic ratios χARM/χlf, ARM/IRM100mT, IRM2T/χlf are not always discriminative, suggesting that (crypto)tephras do not have a single uniform source. Preliminary correlative age models are used to estimate ages for the (crypto)tephras and propose likely associated volcanic eruptions. Finally, strong pedogenic magnetic enhancement of the younger paleosols (S4, S3, S2 and partly S1) contrasts with the smeared and low magnetic signal of the older paleosols (S6 and S5). Moreover, an enhanced content of low-coercivity hematite observed from the upper part of the S5 paleosol upwards to the present and a sharp increase in the concentration of maghemite at the expense of magnetite observed for the S3, S2 and S1 paleosols provides strong evidence for a significant paleoenvironmental change. The timing of this change, based on the SK LPS age models, is compatible with the mid-Brunhes climate transition.

Late Pleistocene Climate and Dust Source From the Mobarakabad Loess–Paleosol Sequence, Northern Foothills of the Alborz Mountains, Northern Iran

Paleoclimatic investigation of loess-paleosol sequences from northern Iran is important for understanding past changes in a region highly sensitive to shifts in precipitation, and along potential routes of past human migration. Here, we present carbon and oxygen isotopic compositions of bulk carbonate (δ13Cbc and δ18Obc, respectively) coupled with particle size distributions of samples from the Mobarakabad section, northern Iran, to study past wind dynamics and hydroclimate. We also present new initial clay-sized Hf-Nd isotope results from key horizons in order to assess general dust sources. Variations of δ13Cbc and δ18Obc values of modern soils compared to paleosols allow reconstruction of late Pleistocene–Holocene climate change in the area. Our results show severe drought during a major eolian deposition phase (EDP) after 34 ka. The thickness and PSD of the C horizon of unit 5 suggest significant shifts in loess sources and depositional environments during this EDP after 34 ka. Indeed, based on our new clay-sized Hf-Nd data, we hypothesize that the loess unit 5 might originate from the young crustal source of the Alborz and Kopet Dagh mountains. In general, the PSD of C horizons in the section is bimodal in the silt fraction and the very small, very fine clay fraction, with a mode at c. 1 μm in the modern soil and paleosols possibly produced by weathering and pedogenic processes. There also appears to be a good correlation between δ13Cbc and δ18Obc values, differentiating phases of loess accumulation and paleosol formation and hence providing quantitative data for reconstructing paleoclimatic conditions in the study area.

Establishing a Luminescence-Based Chronostratigraphy for the Last Glacial-Interglacial Cycle of the Loess-Palaeosol Sequence Achajur (Armenia)

The loess-palaeosol section Achajur is part of the Sevkar loess area in north-eastern Armenia and comprises three prominent pedocomplexes with intercalated loess units, probably spanning at least three glacial-interglacial cycles. With its central position between the Black Sea and the Caspian Sea, the Sevkar loess area serves as important bridge between loess sections in southeastern Europe and Central Asia. Establishing a numerical chronology of the Achajur loess section enables correlation with other loess-palaeosol sections and a palaeoenvironmental reconstruction of the region. In this paper, we focus on the chronology of the last glacial-interglacial cycle using luminescence dating on fine grain (4–11 µm) material. We compare two post-IR-IRSL protocols on polymineral fine grain using different stimulation temperatures, in order to evaluate the influence of fading and potential unbleachable residuals on our samples. For a backup of the younger ages (&amp;lt;50 ka), we also applied a single aliquot protocol on the quartz fine grain fraction. The results indicate that the upper loess unit was deposited during MIS3 and 4, while MIS2 ages are not present. The underlying pedocomplex and loess unit fall into MIS5 and MIS6, respectively. This confirms that the loess was deposited during dry phases and pedocomplexes formed during wetter phases, as is also shown by comparison with other palaeoenvironmental proxies from the area.

Detrital zircon geochronology and provenance of Pleistocene loess and contributing glacial sources, midcontinental USA

Midcontinental North America contains extensive loess deposits that have been studied with geochemical, mineralogical, and stratigraphic techniques to explore glacial history and sediment provenance. Much of this analysis has focused on loess deposits that accumulated during the last glacial maximum (LGM), in part because of the ubiquity of unweathered Peoria Silt deposits. We test the utility of detrital zircon (DZ) U–Pb dating, which offers a weathering-resistant approach to the determination of loess provenance and can uniquely be applied to both LGM and older (commonly more altered) pre-LGM loess units. We determined DZ U–Pb age distributions (n = 1385 U–Pb ages) for the lobes that contributed sediment to Mississippi and Illinois River valley loess: Des Moines Lobe, Superior Lobe, Green Bay Lobe, Lake Michigan Lobe and Huron-Erie Lobe. We also measured DZ U–Pb age distributions (n = 4466 U–Pb ages) sampled from loess sites located along the bluffs of the Illinois River Valley and Mississippi River Valley. Samples were collected from Peoria Silt (Wisconsin Episode; Marine Isotope Stage (MIS 2)), Roxana Silt (Wisconsin Episode; MIS 3), Loveland Silt (Illinois Episode; MIS 6), and Crowley's Ridge Silt (pre-Illinois Episode).LGM glacial tills provide distinct DZ age signatures that can be used to identify glacial source contributions to loess deposits. Loess DZ age signatures in the Peoria Silt of the Illinois River Valley and the Roxana Silt of the northern lower Mississippi River Valley change temporally in a manner consistent with blockage and avulsion of the ancient Mississippi River, representing a proof-of-concept for the DZ loess provenance method in the midcontinent. The loess DZ record also provides insight into the pre-LGM drainage network and glacial lobe extents. DZ signatures for the MIS 3 Roxana Silt, along the Mississippi Valley, implies minimal sediment input from the Des Moines Lobe, suggesting this lobe was short-lived, existed further northward, or provided only limited sediment to meltwater valleys during this time. The dominant Huron-Erie Lobe signature throughout pre-LGM loess units shows that ice flow from the eastern Labrador Dome was a persistent feature during earlier glaciations. Finally, some western-derived DZ ages in pre-MIS 2 loess of the middle and lower Mississippi River Valley suggests that drainage networks that followed the modern Missouri River system were present prior to the LGM and integrated with the Mississippi River system.

A tale of two signals: Global and local influences on the Late Pleistocene loess sequences in Bulgarian Lower Danube

In Central and Eastern Europe, research has been focused on loess associated with a plateau-setting, which preserves distinct and well-developed loess and palaeosol units linked to orbital scale changes. This has led to the view that during the last glacial period the Middle and Lower Danube predominantly experienced dry continental climates and supported steppic environments. However outside of the typical plateau setting, some authors have reported a presence of embryonic palaeosols within loess units suggesting sufficient moisture for short-term pedogenesis, and therefore either large scale moisture delivery systems and/or influence of local climatic and/geomorphic factors. Here the palaeoenvironmental and palaeoclimatic history is reconstructed based on two loess-palaeosol profiles in Slivata, North Bulgaria. The site is located in proximity to both the Carpathian and Balkan Mountains and rest on the Danube river terrace. To understand the timing of sediment deposition and dust fluxes chronological approaches combining quartz optically stimulated luminescence (OSL), feldspar post infrared-infrared stimulated luminescence (pIR-IRSL), and tephra correlation were applied. The results are coupled with high-resolution particle size and magnetic susceptibility analysis to provide an overview of past environmental conditions at the site. Finally, zircon U–Pb ages are used to understand potential changes to sediment delivery patterns, in the context of the site development.The investigated profile at Slivata 2 preserves a loess-palaeosol record spanning 52–30 ka, with a very complex sedimentary sequence that switches between periods of enhanced dust flux and sediment accumulation, and palaeosol development. The Slivata 2 sequence is also punctuated by multiple thin “palaeosol” like units that are interpreted as colluvial “soil” deposits on the basis of sedimentology, provenance, and geochronology, indicating a highly variable and dynamic landscape responding to the surrounding environment. The chronology shows very rapid sediment accumulation at Slivata 1 during LGM, with mass accumulation rates similar to sites in the Carpathian Basin, suggesting strong winds and high sediment supply rates. Yet LGM loess is punctuated by a thin palaeosol, which developed between 20–19 ka. This coincides with a temporary glacial retreat in the Carpathian Mountains and higher moisture availability in Eastern Carpathians, and therefore points to localised influences on loess-palaeosol development. Moreover data from Slivata 1 shows soil development and by extension landscape and climate stabilisation shortly prior to 14 ka. The pre-Holocene onset of pedogenesis at Slivata supports ecological and glacial evidence of weak Younger Dryas from the South Carpathian Mountains.Lastly this paper provides a geochemical analysis of the thin tephra horizon preserved in the Slivata 2 profile, which was correlated to the Cape Riva/Y-2 tephra. Consequently Slivata is the most northerly terrestrial site found to contain this tephra horizon, which has implications for the understanding of the size of the Santorini's Cape-Riva/Y-2 explosion. The identification of the Cape Riva (Y-2) tephra horizon and new remodelled age of 21.92 ± 0.56 cal ka BP provides a new tephrostratigraphic marker for eastern European LGM loess.

Mineral magnetic properties of loess–paleosol couplets of northern Serbia over the last 1.0 Ma

AbstractWe conducted the first detailed mineral magnetic investigation of more than nine loess–paleosol couplets of the composite Titel-Stari Slankamen loess section in Serbia, which provides one of the longest and most complete terrestrial record of paleoclimatic changes in Europe since ~1.0 Ma. The results show that the ferrimagnetic mineral assemblage of the loess units is dominated by partially oxidized multidomain (MD) and pseudo-single domain (PSD) magnetite; however, with an increasing degree of pedogenesis, the eolian contribution is gradually masked by pedogenic superparamagnetic(SP) and single-domain (SD) ferrimagnets (mainly maghemite). The overall consistency of ferrimagnetic grain-size parameters indicates an absence of dissolution of the fine-grained ferrimagnetic fraction despite changes in climate regime over the past 1.0 Ma. The variations of normalized dJ/dT@120Kand normalized χheating@530°Creflect a long-term stepwise increase in aridity during glacials with a major step at ~0.6–0.5 Ma, over the last 1.0 Ma. Overall, the results provide an improved basis for the future use of the magnetic properties of Serbian loess deposits for paleoclimatic reconstruction.

The Požarevac loess–paleosol sequence: a record of increased aridity in the south‐eastern margin of the Carpathian Basin during the last 350 ka

ABSTRACTThe loess sequence preserved in the Požarevac brickyard in north‐eastern Serbia comprises eight loess units separated by seven paleosols. Geochronological investigation using amino acid racemization and luminescence dating support stratigraphic correlations of loess units L3, S2LL1 and L1 at the Požarevac section with loess of glacial cycles E [Marine Isotope Stage (MIS) 10], D (MIS 9–8), C (MIS 7–6) and B (MIS 5–2) across central Europe. Correlation with the marine oxygen‐isotope stratigraphy and associated paleoclimatic inferences are further supported by magnetic susceptibility, particle size and carbonate content measured in Požarevac sediments. Malacological investigations at the Požarevac section reveal the continuous presence of the Chondrula tridens and Helicopsis striata faunal assemblages throughout the last 350 ka. The loess malacological fauna, which is characterized by the complete absence of cold‐resistant and cold‐preferring species, suggests a stable, dry and relatively warm glacial and interglacial climate, compared with other central European loess localities. Together these data suggest that the south‐eastern part of the Carpathian (Pannonian, Middle Danube) Basin was a refugium for warm‐preferring and xerophilous land‐snails during the generally unfavorable glacial climates of the late Middle and Late Pleistocene.

Clay mineralogy of the Stari Slankamen (Serbia) loess-paleosol sequence during the last glacial cycle — Implications for dust provenance and interglacial climate

Clay minerals in loess-paleosol sequences carry important information on dust source and the paleoenvironments of the areas of loess distribution. The loess-paleosol sequences in the Serbian part of the Carpathian Basin are among the most complete Quaternary terrestrial sedimentary sequences in Europe. However, relatively little is known about the origin and temporal variations of clay minerals in these deposits and their paleoclimatic implications. Here we present the results of high-resolution XRD clay mineral analysis of the Stari Slankamen loess-paleosol sequence through the last glacial cycle. The roughly constant composition of the clay minerals within the loess unit and most of the paleosol suggests that the clay minerals are of detrital origin and that pedogenic transformation has only occurred in the lower part of paleosol S1, which corresponds to the climatic optimum of Marine Isotope Stage (MIS) 5e. This provides a basis for addressing several important issues regarding the Carpathian Basin loess, including its provenance, glacial dust activity, and the interglacial climate. The smectite-rich characteristic of the glacial loess provides a diagnostic indicator for confirming local sources for the Carpathian Basin loess deposits, and that these sources made little contribution to the dust deposited in Greenland during the last glacial. The first application of illite crystallinity and the chlorite ratio to the Carpathian Basin loess-paleosol sequence suggests that they are more sensitive indicators than the clay mineral proxies previously used in European loess studies. The enhanced precipitation during MIS 5e indicated by the new proxies and the transformation of clay mineral potentially provide new insights into understanding the regional climatic response to future global warming.