Pedogenic Origin Research Articles

Resolving the Interpretation of Magnetic Coercivity Components From Backfield Isothermal Remanence Curves Using Unmixing of Non‐Linear Preisach Maps: Application to Loess‐Paleosol Sequences

AbstractUnmixing of remanent magnetization curves, either isothermal remanent magnetization (IRM) or backfield IRM, is widely used in rock magnetic and environmental magnetic studies to discriminate between magnetic coercivity components of different origins. However, the wide range of physical properties of natural magnetic particles gives rise to an ambiguous interpretation of these components. To reduce this ambiguity and provide a straightforward interpretation of coercivity components in terms of domain state, interactions, and constituent magnetic phases, we combined backfield IRM unmixing with unmixing of nonlinear Preisach maps for two typical mid‐latitude northern hemisphere loess‐paleosol sequences. Both backfield IRM and nonlinear Preisach maps unmixing are based on the same non‐parametric algorithm, and provide similar endmembers (EMs) in the two sections studied. The first EM (EM1) has a low median coercivity (∼21 mT) and is a non‐interacting single domain (SD) magnetite/maghemite of pedogenic origin. The second EM (EM2) has a moderate median coercivity (∼60 mT) and is a mixture of pseudo‐single domain/multidomain, SD magnetite/maghemite and non‐interacting SD hematite, all of eolian origin. The same EM1 found in both sections suggests that this component's grain size and coercivity are independent of pedogenesis intensity. The same EM2 indicates that a similar magnetic population is being transported and deposited, irrespective of the dust source area and loess granulometry. The approach outlined here provides strong evidence that non‐parametric backfield IRM unmixing isolates physically realistic EMs. Unmixing nonlinear Preisach maps elucidates these EMs in terms of domain states and their constituent magnetic phases.

Soil crust development on playa surfaces of Lake Urmia and its controlling factors: New insights to combat dust sources

The recession of lake shores, including the ones of Lake Urmia (LU), and later exposure of the lake bed sediments to wind erosion as a consequence of climate change and drought, is a devastating phenomenon worldwide. In the absence of stable surface crusts, these areas can be the source of airborne dust causing health and environmental issues. The present study aims at investigating the crust formation and development on Lake Urmia playa (LUP) surfaces through physicochemical and morphological studies and to determine the major factors affecting crust stability. To achieve the above goals, 50 soil crust samples from playa surfaces of the western LU playa were collected. The soil crust thickness and compressive strength were determined by a digital micro penetrometer. By means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), the main morphological and chemical factors responsible for the crust development and evolution in LUP were identified. Results showed that crust samples from clay flats (CFs) and clay flats-salt crusts (CF-SC) possessed the most stable crusts with a thickness of 2.2 and 1.9 cm and maximum compressive strength of 6709 and 7399 kPa, respectively, while sand sheets (Sa-sheets) showed weak and locally restricted crust development. Evaluation of correlation coefficients (CC) between soil crust physicochemical properties and crust stability parameters revealed that clay, silt, and organic matter enhance the crust stability and decrease the erodible fraction by increasing the crust thickness, while salt content quantified as Na+ concentration and electrical conductivity increase the firmness of the crusts. Interestingly, total carbonates quantified as calcium carbonate equivalent (CCE) correlated negatively with crust stability although pedogenic calcite is known as cementing agent in soils. XRD together with FTIR spectroscopy revealed that calcite is indeed the predominant mineral form in most soils with the exception of Sa-sheets with the highest share of carbonates, in which aragonite prevailed over calcite. While carbonates of pedogenic origin act as cementing agent, geologic carbonates present as coarse aragonite particles decrease soil stability. Therefore, samples with the highest total carbonate content exhibited the weakest crust, which explains the negative correlation between soil crust and CCE. SEM coupled with Energy Dispersive X-ray (EDX) and elemental mapping revealed that NaCl is the major cementing agent of the soil particles in crusts developed on LU playa surfaces. Its coexistence with phyllosilicates has increased the crust stability and resilience against wind erosion in CF and CF-SC samples while in the Sa-sheet samples, the absence of clay-size minerals (silt and clay) along with the prevalence of geologic carbonates (dolomite and aragonite) and lower NaCl content, limited crust formation and stability. This study emphasizes the importance of the intrinsic soil physicochemical properties together with the secondary (pedogenic) carbonate formation and more importantly the presence of NaCl, as the best determining factors controlling crust formation over LU playa surfaces.

ВПЛИВ МІГРАЦІЇ ФЛЮЇДІВ НА МАГНІТНУ МІНЕРАЛОГІЮ ҐРУНТІВ

Background. The war in Ukraine arises the urgent need to intensify hydrocarbon production on its own territory in order to maintain and develop the country's energy independence. The effectiveness, low cost and relevance of the involvement are demonstrated by magnetic methods of studies of the near surface geological section and the soil for the oil and gas prospecting. Methods. The methodology of magnetic studies for the hydrocarbon prospecting is based on the methods of studying the environmental magnetism and soil, precision magnetic survey of natural systems and authigenic models of changes in magnetic mineralogy under the influence of hydrocarbon fluid migration. Results. The crucial aim is to distinguish the sources of the formation of the magnetic minerals. In most cases, soils contain minerals of natural pedogenic origin, authigenic secondary magnetic minerals, and sometimes detrital fine-coarse magnetic phases. For Ukraine, magnetite, maghemite, hematite, and goethite are the most common magnetic minerals of soils of the pedogenic origin. At the same time, the experience of conducting magnetic mineralogical analyzes of soils in the territories of oil and gas deposits indicates the presence of iron sulfides. First of all, monoclinic pyrrhotite is identified. The soils also contain accompanying hexagonal pyrrhotite, pyrite, and greigite. The results of thermomagnetic analyzes and hysteresis loops of soil samples collected at the territories of hydrocarbon deposits are presented and their mineral composition is analyzed. Conclusions. The results of the study of the impact of hydrocarbon fluid migration (microseepage) on the change in the mineral composition of soils indicate significant informativeness and the perspective of introducing the method into the complex of geological exploration works at various stages. Authigenic changes of magnetic minerals in the near surface geological section and soil, as well as natural and anthropogenic accumulation of hydrocarbon products in soils, cause changes in magnetic properties and form magnetic field anomalies.

The geomorphology and neotectonics of the Vaalputs Radioactive Waste Disposal Facility site, Namaqualand, South Africa: Palaeoseismological and geodynamic implications

Abstract The safe disposal of radioactive waste products remains a challenging and controversial issue, yet their burial in a stable geological environment is the option favoured by most countries. Past investigations of the Vaalputs facility in South Africa’s semi-arid Bushmanland Plateau demonstrated its suitability for the disposal of low-level, short-lived (<300 years) radioactive waste, but also the need for more data on hazardous seismotectonic and climatic processes for the potential storage of longer-lived spent nuclear fuel. We review and then provide new information on the regional geomorphological and morphotectonic features of the Bushmanland Plateau, focusing on pedogenic features and compressive shear fractures in the trenches excavated over the past two decades. The fractures, provisionally dated between ~75 ka and ~46 ka, resemble east-verging thrust faults of limited horizontal displacement (≤1 m) and die out at depths of 4 m. Having discounted a pedogenic origin, the shear fractures likely represent stress relief structures triggered by the seismogenic reactivation of one of the Quaternary active faults in the area. The most likely candidate is the Santab Fault Zone (SFZ), which has a strike length ≥20 km and a throw of up to ~5 m at its closest point (8 km) to the Vaalputs site. Regional remote sensing and off-site investigations in the Bushmanland Plateau relate the neotectonic episodes at Vaalputs and environs to a late Pleistocene climax of the Namaqualand seismic source zone. This zone is characterised by the Wegener Stress Anomaly, a long-lived ~northwest-southeast oriented compression that, at its apex in the Late Santonian, caused large scale folding and thrusting not only in Bushmanland and parts of central-southern Namibia, but also swept across the entire African plate.

Identifying Detrital and Diagenetic Minerals in Paleosols of the Illinois Basin

Phyllosilicates are hypothesized to be primarily of pedogenic origin in shallowly buried paleosols (≤3 km depth), regardless of the age of the paleosol. To test this hypothesis, this work evaluates the possible presence of detrital and diagenetic phyllosilicates in middle and upper Pennsylvanian paleosols, collected from three drill cores along a north–south transect in the Illinois Basin. The abundances of 2M1 muscovite, quartz, and K-feldspar are greater in a morphologically immature Protosol from the southernmost core; 1Md illite and interstratified illite-smectite with R1 and R0 stacking orders are more abundant in the more mature Vertisols of the central and northern cores. K-Ar age values of multiple clay-size fractions from each paleosol averaged ~260 Ma in the northern core, 270 Ma in the central core, and 295 Ma in the southern core. While considering the complex tectonic and thermal history of the Illinois Basin, detrital minerals are more abundant in immature paleosols that experienced relatively greater maximum burial depths and thus greater sediment supply whereas illitization in more mature paleosols was probably initiated primarily during protracted burial diagenesis. As the present study found evidence for diagenetic and detrital minerals in clay-size fractions of shallowly buried, deep-time paleosols, caution is advised when using paleosol minerals for ancient climate and environment reconstructions.

The origin and transformation of soil lamellae in calcareous and non-calcareous loess soils in the Central European loess belt – A case study from southern Poland

Loess in Europe is heterogeneous due to differences in paleoenvironmental conditions during sedimentation and pedogenesis. In many regions of Europe, including southern Poland, loess accumulation was followed by the leaching of carbonates followed by clay translocation, which is typical in silty soils in humid climates. Loess soils in the temperate climate zone are characterized by the presence of well-developed or well-preserved microfabrics of different origin but with similar morphology, among which lamellae can be distinguished. Lamellae commonly occur in loess soils; however, detailed studies focused on their origin and evolution are lacking. The main aim of the present study was to determine the origin and transformation of lamellae both in calcareous and non-calcareous loess soils in the Central European loess belt, using an example from southern Poland. The following three hypotheses were tested: (1) decalcification of the upper part of loess soils is a necessary condition for soil lamellae formation, while frost action is not a key factor shaping their morphology and properties in the Central European loess belt, (2) occurrence of carbonate in the lower part of calcareous loess soils inhibits lamellae formation, (3) soil lamellae are transformed due to bioturbation and shrinking-swelling processes in both calcareous and non-calcareous loess soils. The obtained results indicate that decalcification of the upper part of calcareous loess soils enables the translocation of clay particles and lamellae formation. Field observations and micromorphological analysis indicate that the presence of carbonate limits the development of soil lamellae and constitutes a barrier to deeper clay translocation in loess soils. This finding suggests a pedogenic origin of lamellae in the loess soils of southern Poland. Soil lamellae show a number of signs indicating their mechanical degradation due to swelling and shrinking, bioturbation, and dissolution driven by eluviation and redox processes. The progressive evolution of lamellae leads to an enhancement of their expression in the illuvial Bt and transitional BC horizons.

Effects of turning rainforest into oil-palm plantations on silicon pools in soils within the first 20 years after the transformation

Potential effects of land-use/land-cover (LULC) transformation from lowland rainforest into oil-palm plantations on silicon (Si) pools in tropical soils remain poorly understood, although appropriate levels of plant-available Si in soils may contribute to maintain high crop yields and increase the vitality and drought resistance of oil palms. Therefore, the aim of our study was to identify possible effects of such LULC change on soil Si pools. For this purpose, we compared soil Si pools under lowland rainforest and ca. 20 year-old oil-palm plantations in Jambi Province, Indonesia. The investigated soils were Acrisols and Stagnosols, in which we quantified six different soil Si pools following a sequential extraction procedure to evaluate, whether 20 years of oil-palm cultivation has led to a depletion of these soil Si pools. The considered pools included mobile Si, adsorbed Si, Si bound in soil organic matter (SOM), Si included in pedogenic oxides and hydroxides, and Si in amorphous silica of biogenic and pedogenic origin. Finally, we also determined total Si. All oil-palm plantations established on sloping terrain and Acrisols only showed decreased Si stocks of mobile Si, adsorbed Si and SOM-bound Si; those established in floodplains and Stagnosols had decreased stocks of SOM-bound Si and biogenic-amorphous silica. Lower Si stocks were mostly attributed to a missing “stable” phytolith pool in the subsoil and less organic matter in topsoils under oil-palm plantations. When comparing well-drained and riparian areas, flooding seemed to increase phytolith dissolution. We conclude that 20 years of oil-palm cultivation has not yet led to a significant depletion of soil Si pools. As topsoils comprise the highest concentrations of SOM-bound Si and Si in amorphous silica of biogenic origin but are susceptible to erosion and surface runoff under managed oil-palm plantations, it would be advisable to instate specific management practices that maintain organic-rich and well-aired topsoils on oil-palm plantations.

Sedimentological and geochemical properties of authigenic carbonates in Kyushu, Japan: Implications for the transition from semi-arid to humid climate during the Eocene

The timing of the East Asian monsoon system has attracted attention because of the possible relationship between the tectonic uplift of the Himalaya and Tibetan Plateau and climatic evolution in East Asia. Although the existence of the East Asian monsoon in the late Eocene has recently been suggested, few paleoclimatic records have been reported from the mid-latitude coastal area in East Asia where the climate might have changed dramatically when the East Asian monsoon was established. In this study, we examined the climatic conditions in the early and late Eocene at two localities in the northern part of Kyushu, Japan, focusing on the depositional environments of freshwater carbonate nodules. The lower Eocene Akasaki Formation yields dolomite and calcite nodules in the red mudstone layers, which record low δ13C and variable δ18O. The geochemical and textural features of the nodules suggest a pedogenic origin, which we interpreted as indicating formation on a floodplain with well-drained soils under a semi-arid climate with seasonal precipitation. In contrast, the upper Eocene Yoshinotani Formation yielded nodules composed of siderite with distinctively positive δ13C and stable δ18O values, suggesting that they developed on wetlands covered by poorly drained soils in a temperate climate with stable rainfall throughout the year. These two types of nodule-bearing formations imply that the climate became wet in the middle Eocene. This climate change in Kyushu predated the rapid global cooling at the Eocene-Oligocene transition and may be related to the appearance of the monsoon system in East Asia, which was caused by the uplift of the Himalaya and Tibetan Plateau.

Multivariate Urban Air Quality Assessment of Indoor and Outdoor Environments at Chennai Metropolis in South India

The present study examines indoor and outdoor environmental particulate matter and gaseous pollutants in order to evaluate the urban air quality, the sources and pathways of pollutants, and its impact on Chennai megacity, South India. A total number of 25 air conditioner filter particulate matter samples collected from residential buildings, schools, colleges, commercial shopping malls, and buildings near urban highways were studied for indoor air quality. Similarly, outdoor air quality assessments have been done in various parts of the Chennai metropolis, including the Manali-Industrial area, the Velachery-Residential site, and the Alandur Bus Depot, as well as collected air quality data sets from the Central Pollution Control Board at continuous ambient air quality monitoring stations. The suspended atmospheric particles where the highest concentration (47%) occurred were mostly located in the roadside environments followed by commercial areas (42%), which indicates the increase in air pollution in the roadside areas. Further, environmental magnetism and ecological risk indices were studied from the collected data set. The study predicts that the air pollutants were predominantly from anthropogenic sources, such as vehicle emissions, effluents from power plants, abrasion of tires, steelworks, burning of fossil fuels and construction materials, etc. As a result, the current study suggests 68% of indoor pollutants were from the anthropogenic input, 18% from the pedogenic origin, and 14% from high heavy metal pollution at the sampling sites. This indicates that raising the ventilation rate via mechanical components significantly enhances the indoor air quality. These findings might be valuable in improving urban air quality, reducing traffic-related pollutants, and improving environmental quality.

Removal of atmospheric CO2 by engineered soils in infrastructure projects

The use of crushed basic igneous rock and crushed concrete for enhanced rock weathering and to facilitate pedogenic carbonate precipitation provides a promising method of carbon sequestration. However, many of the controls on precipitation and subsequent effects on soil properties remain poorly understood. In this study, engineered soil plots, with different ratios of concrete or dolerite combined with sand, have been used to investigate relationships between sequestered inorganic carbon and geotechnical properties, over a two-year period. Cone penetration tests with porewater pressure measurements (CPTu) were conducted to determine changes in tip resistance and pore pressure. C and O isotope analysis was carried out to confirm the pedogenic origin of carbonate minerals. TIC analysis shows greater precipitation of pedogenic carbonate in plots containing concrete than those with dolerite, with the highest sequestration values of plots containing each material being equivalent to 33.7 t C ha−1 yr−1 and 17.5 t C ha−1 yr−1, respectively, calculated from extrapolation of results derived from the TIC analysis. TIC content showed reduction or remained unchanged for the top 0.1 m of soil; at a depth of 0.2 m however, for dolerite plots, a pattern of seasonal accumulation and loss of TIC emerged. CPTu tip resistance measurements showed that the presence of carbonates had no observable effect on penetration resistance, and in the case of porewater pressure measurements, carbonate precipitation does not change the permeability of the substrate, and so does not affect drainage. The results of this study indicate that both the addition of dolerite and concrete serve to enhance CO2 removal in soils, that soil temperature appears to be a control on TIC precipitation, and that mineral carbonation in constructed soils does not lead to reduced drainage or an increased risk of flooding.

Polyarenes Distribution in the Soil-Plant System of Reindeer Pastures in the Polar Urals

Humic substances of soils consist of various organic compounds, including polycyclic aromatic hydrocarbons (PAHs). Soil as a fairly stable medium allows the correct use of polyarenes as markers of the humus formation process. Monitoring of the accumulation of PAHs as resistant organic toxicants is also necessary due to their carcinogenic and mutagenic properties. Natural plant resources serve as the feed base of northern reindeer husbandry. In this study, high-performance liquid chromatography in a gradient mode and gas chromatography-mass spectrometry methods were used to estimate the content of PAHs in mountain tundra and meadows of the Polar Urals (Russia). The accumulation of polyarenes in soils on carbonate rocks of the Bolshoi Paipudynsky ridge occurs mainly in the process of soil formation and largely depends on factors such as productivity of plant communities, the composition of standing biomass, the site’s position in relief, the granulometric composition of soils, cryogenesis process and pyrogenesis. According to the set of polyarenes, their number, and ratio, the studied objects were classified into separate groups by discriminant analysis. The most typical representatives of pedogenic origin are naphthalene and phenanthrene. The accumulation features of dibenz[a,h]anthracene and benz[b]-, benz[k]fluoranthene, benz[ghi]perylene, and benz[a]perylene are shown. In mountain tundra landscapes, the characteristics of PAHs can be used to diagnose the intensity and direction of soil formation processes in general and humification in particular.

Sources of CO2 Produced in Freshly Thawed Pleistocene-Age Yedoma Permafrost

The release of greenhouse gases from the large organic carbon stock in permafrost deposits in the circumarctic regions may accelerate global warming upon thaw. The extent of this positive climate feedback is thought to be largely controlled by the microbial degradability of the organic matter preserved in these sediments. In addition, weathering and oxidation processes may release inorganic carbon preserved in permafrost sediments as CO2, which is generally not accounted for. We used 13C and 14C analysis and isotopic mass balances to differentiate and quantify organic and inorganic carbon released as CO2 in the field from an active retrogressive thaw slump of Pleistocene-age Yedoma and during a 1.5-years incubation experiment. The results reveal that the dominant source of the CO2 released from freshly thawed Yedoma exposed as thaw mound is Pleistocene-age organic matter (48–80%) and to a lesser extent modern organic substrate (3–34%). A significant portion of the CO2 originated from inorganic carbon in the Yedoma (17–26%). The mixing of young, active layer material with Yedoma at a site on the slump floor led to the preferential mineralization of this young organic carbon source. Admixtures of younger organic substrates in the Yedoma thaw mound were small and thus rapidly consumed as shown by lower contributions to the CO2 produced during few weeks of aerobic incubation at 4°C corresponding to approximately one thaw season. Future CO2 fluxes from the freshly thawed Yedoma will contain higher proportions of ancient inorganic (22%) and organic carbon (61–78%) as suggested by the results at the end, after 1.5 years of incubation. The increasing contribution of inorganic carbon during the incubation is favored by the accumulation of organic acids from microbial organic matter degradation resulting in lower pH values and, in consequence, in inorganic carbon dissolution. Because part of the inorganic carbon pool is assumed to be of pedogenic origin, these emissions would ultimately not alter carbon budgets. The results of this study highlight the preferential degradation of younger organic substrates in freshly thawed Yedoma, if available, and a substantial release of CO2 from inorganic sources.

Silicon mobilisation by root-released carboxylates.

Plants have evolved numerous strategies to acquire poorly available nutrients from soil, including the release of carboxylates from their roots. Silicon (Si) release from mineral dissolution increases in the presence of chelating substances, and recent evidence shows that leaf [Si] increases markedly in old phosphorus (P)-depleted soils, where many species exhibit carboxylate-releasing strategies, compared with younger P-richer soils. Here, we propose that root-released carboxylates, and more generally rhizosphere processes, play an overlooked role in plant Si accumulation by increasing soil Si mobilisation from minerals. We suggest that Si mobilisation is costly in terms of carbon but becomes cheaper if those costs are already met to acquire poorly available P. Uptake of the mobilised Si by roots will then depend on whether they express Si transporters.

Genesis of lamellae in sandy soils: A case study in a semi-arid region in NE-Brazil

The occurrence of lamellae in soils and sediments has direct implications for agricultural production, and for stratigraphic and geomorphological studies. Although lamellae have been studied for more than a century, their origin remains controversial. The aim of this study was to identify the origin and formation mechanisms of lamellae in autochthonous soils developed from metamorphic rocks in a semi-arid area of Northeast Brazil. As such, the spatial organization of soil profiles was evaluated in a topolithosequence, through structural analysis of the pedological coverage for subsequent soil sampling. Morphological, chemical, physical, sedimentological, mineralogical, and micromorphological analyses were carried out on the studied slope and in greater detail in four soil profiles. The results indicated that clay particles predominantly smaller than 0.2 µm are eluviated in a sandy soil matrix, infilling voids and coating quartz grains, which are organized in layers of densely packed fine sand, impeding clay translocation and helping form lamellae. Although the micromorphological properties of the lamellae demonstrate their pedogenic origin, the contribution of strips of polycrystalline quartz constitutes a petrogenic component of the illuviation process. Therefore, the genesis of the lamellae is better described based on a petro-pedogenic origin. We suggest a restructuring of the concept of petro-pedogenic origins, including the structural influence of metamorphic rocks, as illuviated clay deposition occurs in accordance with a physical barrier provoked by the increase and organization of fine sand particles, distributed horizontally and in parallel, arising from the disintegration of polycrystalline quartz grains, which indicates geological control in the genesis of lamellae, corresponding to petrogenic evidence. Furthermore, the morphological distinction of the lamellae seems to be more associated with the fine sand content (<0.25 mm), and its packing with larger grains of quartz in the soils.

Mineralogical and physico-chemical characterization of gypsiferous semi-arid soils in the north of Urmia, Iran

Gypsiferous soils contain sufficient gypsum to influence soil physico-chemical, mineralogical, mechanical properties and geotechnical conditions and as a consequence, affect plant growth and crop production. So physico-chemical and mineralogical properties of 6 soil profiles located on the gypsiferous parent material with semi-arid climate in north of Urmia, West Azerbaijan province, Iran, were investigated. Based on standard methods, morphological, physico-chemical and mineralogical properties of these soils were determined. Soils with higher gypsum content had lighter color, lighter texture, lower values of organic carbon and cation exchange capacity and higher values of electrical conductivity. These parameters were reversely changed with decreasing gypsum content of soils. Semi-quantitative analysis of clay minerals indicated the presence of smectite, illite, chlorite, kaolinite and palygorskite were as major clay minerals with decreasing order from smectite to palygorskite. The origin of illite, chlorite and kaolinite were related to the inheritance from parent material. Smectite group of clay minerals has been resulted from three origins of inheritance from parent material, transformation of illite and palygorskite and neoformation, but the transformation and neoformation are the main pathways for its formation. Palygorskite has pedogenic origin and has been formed via neoformation. The comparison of clay mineralogy of soils with different gypsum values revealed the presence of higher smectites in soils with higher gypsum. Palygorskite was identified just in soils with higher gypsum. In soils with lower values of gypsum, illite and chlorite were the predominant clay minerals and palygorskite did not identified.

High-resolution palaeoenvironmental reconstruction at Zmajevac (Croatia) over the last three glacial/interglacial cycles

A high-resolution analysis of the Zmajevac loess-palaeosol sequence in East Croatia (Baranja) was performed with the purpose to get new insights into the palaeoenvironmental history during the last three glacial-interglacial cycles. The post-IR infrared stimulated luminescence signal of feldspar, stimulated at 290°C (thereafter pIRIR290) was used to establish a reliable chronological framework and revealed intensive sedimentation during (at least) the last 300 kyr, which was five times interrupted by climate optima resulting in the formation of soils (now palaeosols). The environmental magnetic measurements support the obtained luminescence chronology. Further chronological time control was reached by age modelling based on tie points from variations in frequency dependence of magnetic susceptibility and benthic δ18O variations from the LR04 stack of Lisiecki and Raymo (2005). The grain-size record provided information about the environmental conditions and dust accumulation. Additional palaeoenvironmental implications were provided by room temperature magnetic susceptibility and colourimetric analyses and revealed a continuously lower intensity of pedogenesis, coupled with constantly decreasing temperatures and precipitation from the oxygen isotope stage (OIS) 9 to the end of OIS 3. X-ray diffraction of the clay mineral fraction revealed chlorite, smectite and illitic material as dominant mineral phases. While clay minerals from loess are mostly detrital, smectite from palaeosols is partly of a pedogenic origin. The application of our multi-proxy approach, including relative and numerical dating techniques, provided new insights into a highly resolved terrestrial paleoenvironmental record of Eastern Croatia.

The Santa Vitória Alloformation: an update on a Pleistocene fossil-rich unit in Southern Brazil

The Santa Vitória Formation is a lithostratigraphic unit known for its fossil assemblage of Pleistocene mammals, established in 1973 from sediments exposed along the banks of Chuí Creek, in the southern coastal plain of the state of Rio Grande do Sul (CPRS), Brazil. The original description was presented in a Masters’ dissertation and never formally described in a peer-reviewed publication. Moreover, surveys and fossil collecting efforts developed in the last decade have led to a better understanding of its origin and nature. An updated description of this unit is presented here, which outcrops in areas occupied by barrier-lagoon depositional systems originated by eustatic oscillations. The formation encompasses Middle-Upper Pleistocene fluvial and eolian depositional systems and paleosols formed chiefly of fine to medium quartz sand, with subordinate clay, concentrations of iron and manganese oxides, and caliche nodules of pedogenic origin. It conformably overlies upper shoreface-foreshore marine deposits, and is overlain by loess deposited during the last glacial period. Here is proposed to re-define it as Santa Vitória Alloformation, considering that the use of an allostratigraphic framework to characterize this unit has the practical purpose of grouping depositional systems genetically unrelated to the barrier-lagoon systems.

Changes in the Magnetic Properties of Soddy-Podzolic Soils Depending on the Conditions of Soil Formation

This paper presents the results of a study of soil cover in the Mari Chodra national park in the southeastern part of the Republic of Mari El. Magnetic properties of soddy-medium-podzolic sandy loam soils and soddy-podzolic loam soils are studied. Samples are taken along the shoreline of the karst Yalchik Lake and up the slope from the lake. Based on the results of magnetic susceptibility measurements, it is shown that the studied soil profiles are characterized by both the accumulative and eluvial–illuvial distribution of mineral components, depending on the conditions of soil formation and recreational activity of the given territory. It is shown that the increase in magnetic susceptibility in the organogenic horizons of soddy-medium-podzolic and soddy-podzolic soils is due to the contribution of a ferrimagnetic component. Differential thermomagnetic analysis and decomposition of coercive spectra into components revealed that the main carriers of the magnetization of the soils are fine-grained magnetite and hematite that have a pedogenic origin.

Major and trace elements, δ13C, and polycyclic aromatic hydrocarbons in the Late Pleistocene ice wedges: A case-study of Batagay yedoma, Central Yakutia

We studied the ionic composition of ice, the content of suspended and dissolved trace- and major elements in ice, values of δ13С, and the composition of PAHs of inclusions in the Late Pleistocene syngenetic ice wedges of the Batagay yedoma. For the first time, the complex geochemical study of Batagay megaslump was carried out. The ice of the upper and lower complex of different ages was studied. Mineralisation of the Late Pleistocene ice wedges of Batagay yedoma ranges from 66.56 to 424.8 mg L−1, from ultrafresh to desalinated, the ionic composition of the ice is bicarbonate-calcium and corresponds to snow formed under the influence of continental air masses. The proportion of Ca contained in dissolved form is not more than 20–30%; as for the other elements, the proportion of Mg, K, Na, Al, Fe, Mn, Sr, Ba in suspended form is greater than 90%. The content of trace elements in inclusions in ice wedges and soils is equal, which confirms the pedogenic origin of the inclusions in ice. According to our data, values of δ13С in lipids of the pedogenic material in ice decrease with depth. The lowest values (values of δ13С less than −30‰) were observed in the ice wedge of the upper complex at a depth of 7.4–8.6 m. The increase of δ13C values of lipids from pedogenic material in ice wedges with depth is due to the landscape change from grassland ecosystems to forest ecosystems, and may also be influenced by the increased frequency of fires that occurred during the transition to forest ecosystems and the disappearance of large herbivores.

Pedogenic origin of Mezezo opal hosted in Ethiopian Miocene rhyolites

ABSTRACT Opals are widespread within Miocene volcanic sequences in the North Shoa province of Central Ethiopia. The opal occurs as cavity fillings in a 5 m thick seam of glassy rhyolitic ignimbrite that is sandwiched between basaltic lava flows. The opals occur over a large area (&amp;gt;25 km2). X-ray diffraction analyses show that they are CT-type. The opals contain lower concentrations of trace elements (up to 100 times) than the host rhyolite. Ratios of most trace elements are, however, similar in both the opals and rhyolites. The opals have high δ18O values (28.4–33.8‰) that imply a low temperature of formation, between 20.55 and 25.74 °C. We therefore propose that the opals precipitated from meteoric waters that had percolated through and interacted with the host rhyolite. Field evidence indicates that this weathering and alteration occurred immediately after emplacement of the rhyolites, but prior to the extrusion of the overlying basalt flows.