Recent Bottom Sediments Research Articles

Biostratigraphy of Late Holocene bottom sediments from the Northern part of Chukchi Sea

The research goal is the investigation of environmental processes of recent sedimentation in the Arctic Ocean area. A short core (length – 37 cm) was taken from the Northern part of the Chukchi Sea. Analytical methods included macroscopic sedimentological description by smear-slides, dating by γ-measurements of 137Cs and 210Pb, diatom and palynological analyses. Sedimentation rates at the research site have been determined to be 1 mm y-1. Thus, the age of the cored sediments spans approximately 400 years, which includes the period of the Little Ice Age. Abundant cold-water diatom species and spores of terrestrial plants within the lower part of the sediment core are characteristic for cold climate conditions, which dominated the Little Ice Age. The occurrence of Jurassic, Cretaceous, and Neogene species of spores and pollen in the Holocene deposits are the evidence of coastal abrasion and the subsequent transfer of the material to the coring site by currents. Southern, subtropical, and tropical species of diatoms within the upper, more recent part of the core reveal the transfer of material by currents from the Pacific Ocean to the Arctic Ocean through the Bering Strait. The results of biostratigraphic analyses indicate environmental changes during the last 400 years, revealed in bottom sediments of the Northern part of the Chukchi Sea.

Paleogeography and Natural Environment of the Karelian Coast of the White Sea in the Holocene According to the Study of Lake Sediments Near the Mouth of the Keret River

The article presents the results of a comprehensive (diatom and spore-pollen analysis and 14C-dating) study of the Holocene bottom sediments of a lake located on the coast of the Kandalaksha Bay of the White Sea near the mouth of the Keret River. Three stages in the development of the lake basin have been identified: marine, transitional, and lacustrine. Diatom assemblages characteristic of each facies are given. The indicator value of pollen, spores and non-pollen palynomorphs for identifying marine, transitional and freshwater sedimentation conditions is noted. A decrease in sea level was established at the turn of 7200 calendar years ago. The change of the marine environment of sedimentation to the lacustrine was recorded approximately at the turn of 6700 calendar years ago. For a given time, the position of the coastline of the sea is shown within the studied coast. The data of spore-pollen analysis were used for relative dating of post-glacial deposits. Vegetation was reconstructed from the end of the early Holocene to the present.

Carbonate Sedimentation in High-Mineralized Lake Bolshoi Bagan (South of West Siberia): Dependence on Holocene Climate Changes

Abstract ––We present the results of comprehensive studies of Holocene bottom sediments from the shallow hypersaline (mineralization up to 282 g/L) Lake Bolshoi Bagan, located in the East Baraba lowland (south of Western Siberia). The research methods include X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, scanning electron microscopy, elemental analysis of sediments and pore water, radiocarbon (14C AMS) dating. It has been found that during the Holocene an intensive authigenic mineral formation took place in the lake basin; gypsum, halite and carbonates of calcite-dolomite series dominate among the newly formed mineral phases. Mg-calcites with different Mg contents, excess-Ca dolomites, aragonite and occasionally Mg-siderite have been found in the assemblage of carbonate minerals by mathematical modeling of complex XRD patterns. Mineralogical and crystallochemical studies, supplemented by the results of geochemical analyses, allowed us to identify four stages of the evolution of Lake Bolshoi Bagan in the Holocene, due to regional climate variations. The boundaries of the stages in general correspond to the boundaries of the climatostratigraphic phases by the Blytt–Sernander system: Stage I (the end of the Boreal) – the lake formation, humid climate; Stage II (Atlantic) – climate aridization, shallowing of the lake; Stage III (Subboreal) – unstable climate, frequent change of conditions; Stage IV (Subatlantic) – moderately cool and dry climate.

Composition of Late Holocene Deposits of Southern Part of the Chukchi Sea

The aim of the study was comprehensive study of Late Holocene bottom sediments from the southern part of the Chukchi Sea and reconstruction of the conditions of their accumulation. Analytical methods included macroscopic description with smear slides inspection, 210Pb dating of the sediments, determination of biogenic components, magnetic susceptibility measurements, grain size distribution, palynological and mineral analyzes. The rate of modern sedimentation established at the study point is 8–10 mm/year. Sediments are mainly represented by silts. In the upper part of the core, there are increased concentrations of SiO2biog, Corg, Ntot and decreased values of magnetic susceptibility. This is probably due to the increased bioproductivity of the Chukchi Sea during last years, caused by the current climate warming. The palynological composition of the studied deposits reflects the tundra and forest-tundra vegetation on land adjacent to the Chukchi Sea. The presence of Neogene pollen in the Late Holocene sediments is evidence of their transfer from eroded ancient sediments.

Distribution of palynomorphs in recent bottom sediments offshore Niger delta: A preliminary study

A palynological and sedimentological study of recent bottom sediments from shallow proximal and distal locations offshore Niger Delta was carried out in order to assess the distribution of palynomorphs viz-a-viz the lithofacies in the study area. Fractions of the sediments were subjected to standard laboratory treatments to recover palynomorphs and to make deductions on their lithofacies types. The salinity and pH values of the sediments were also recorded. The most abundant palynomorphs recovered were those of Poaceae, Rhizophora, Elaeis guineensis, Alchornea cordifolia, and spores of fern species. Four lithofacies types were recognized across the locations. They are: Poorly sorted sands (I), Moderately sorted sands (II), Hard textured shale (III) and Sandy shale (IV). Shallow distal locations recorded higher proportions of palynomorphs than deeper proximal locations. Distal location A1 had the highest number of palynomorphs while proximal location B4 is devoid of palynomorphs. The result also revealed that sandy samples from proximal locations (B2,4,5,6) had paucity of palynomorphs; samples with mixture of sand and shale i.e., paralic (B1, 3 and A4) had moderately abundant palynomorphs while shaly samples in distal locations A1, 2, 3 had the highest number of palynomorphs. Seafloor morphology/topography made different areas to have different lithofacies at the same period, hence, low palynomorph recovery in sandy deposits may not always indicate dry paleoclimate condition of source area. Palynomorph abundance in the sediments studied seems to be guided primarily by lithofacies and salinity.

Climate signals in the Holocene bottom sediments of shallow saline lakes of the Southwestern Siberia

Abstract. We present the results of the study of the Holocene sediments from two shal low lakes of different salinity located in the East Baraba lowland (Southwestern Siberia). The research methods: X-ray diffractometry (XRD), IR spectroscopy, laser particle size analysis, AMS dating, etc. By the mathematical modeling of complex XRD patterns Mg-calcites with different Mg contents, excess-Ca dolomite and aragonite have been established in the assemblages of carbonate minerals. Based on studies of mineralogical-crystallochemical features and quantitative ratios of Ca-Mg carbonates the evolution stages of lakes corresponding to the regional cycles of aridization/humidization were identified and the correlations with global climatic events were carried out. The obtained results is an important source of new information about the Holocene climate in the Southwestern Siberia.

BIOGENIC SILICA SEDIMENTATION ON THE SHELF AND CONTINENTAL SLOPE OF THE BLACK SEA

Investigation of the marine sediments processes, regularities of their accumulation in the inland seas is one of the main tasks of marine geology and sedimentology. Biogenic sedimentation is extremely important in the general sediment deposition cycle in the Black Sea basin. This article provides an overview of the literature and analysis of our own research of the distribution of biogenic siliceous deposits in Holocene bottom sediments on the shelf and continental slope of the Black Sea. The composition and conditions of biosilicates formation, their relationship with coccolithic silts and sapropels in sedimentary strata, sources and forms of siliceous biogenic matter input, the dynamics of transformation of modern bottom sediments, as well as the influence of various environmental factors on the process of sedimentary accumulation of silica in the Black Sea basin in the late quarter are considered. The relevance of the topic is caused by insufficient coverage of a number of issues regarding the sources of mobilization and the nature of material input, the features of the origin and deposition of silicate biogenic matter in the basin, paleogeoecological factors that influenced on sedimentogenesis in the late Quarter. The study of the formation processes of modern bottom sediments in a wide range of facies conditions is of undoubted practical importance for diverse geological, sedimentological and facies research, both fundamental and applied, related to prospecting, exploration and exploitation of minerals, as well as for using the results obtained in the development of marine water area.

Таксономическое разнообразие диатомовых комплексов голоценовых донных отложений малых водоемов депрессии озера Имандра

Исследования таксономического разнообразия диатомовых водорослей в голоценовых донных отложениях двух малых водоемов на западном побережье оз. Бабинская Имандра (Мурманская область) продемонстрировало исторические трансформации видового состава и структуры диатомовых комплексов в ответ на меняющиеся условия окружающей среды в голоцене. Изученные водоемы характеризовались доминированием бентосных форм и обрастателей в составе палеосообществ на протяжении всего голоцена. Наиболее резкие изменения в диатомовых комплексах были вызваны тектоническим событием в зоне Имандровской депрессии.

Mineralogical and geochemical composition of Late Holocene bottom sediments of Lake Onego

The analysis of both the mineralogical and geochemical composition and the stratigraphy of Holocene sediments of Lake Onego provided a novel interpretation of their genesis. Their mineral composition suggests that Holocene bottom sediments generally inherit the composition of terrigenous material that enters the lake with river runoff. The predominant authigenic minerals include biogenic opal from diatom skeletons, Fe-illite, and Fe-chlorite, which are the main iron mineral forms in bottom sediments of Lake Onego. Unstable suspension components (illite and chlorite) transform into their ferruginous varieties under humid climate conditions and high concentrations of iron and silicon in the lake waters. Both the presence of ferromanganese nodules in the uppermost part of bottom sediments of Lake Onego and their formation result from the location of the lake in the northern humid zone, geological composition of Fennoscandian crystalline rocks on the Lake Onego watershed, and the presence of an oxidative geochemical barrier into the lake sediment sequence. Late Holocene bottom sediments are represented by two types of sequences: 1) Fe-Mn enriched layers are formed near the sediment-water interface under oxygenated near bottom waters, and 2) such layers are not formed due to low concentrations of oxygen in water; but there are also non-laminated, homogeneous greyish-green silts, similar to those present in the lower parts of the first type of cores. Sedimentation rates (~0.10 cm y−1) were determined by 210Pb- and 137Cs geochronologies.

Composition of recent bottom sediments of the Chukchi Sea. Results of an integrated sedimentological research

Results of high-resolution research of recent bottom sediments from south, central and north Chukchi Sea reveal striking data on environmental changes during the last decades. The composition of surface sediments from the Arctic Sea gives evidence of the decrease of ice cover and an increase of biogenic elements, caused by higher bioproductivity.

Hydrocarbon molecular markers in the Holocene bottom sediments of the Barents Sea as indicators of natural and anthropogenic impacts.

The recent intensification of energy resource exploration and human activities in the Barents Sea (BS) requires a more thorough assessment of the natural and anthropogenic impact of hydrocarbons on the environment. We analyzed a wide set of sensitive indicators, including hydrocarbon molecular markers and organic matter (OM) maturity parameters in the Holocene sediments from three regions of the BS: the Kola-Kanin Monocline (KKM), the Svalbard shelf, and the Shtokman gas-condensate field (GCF). An increase in pyrogenic polycyclic aromatic hydrocarbons toward the core surface traces the intensification of anthropogenic contamination in the KKM region during last century. An input of highly mature OM from the eroded coal rocks of Barentsburg were confirmed by comparison of biomarker distribution in sediments and coals. An increase in biogenic hopanes and hopenes content down-core, and a crude-oil stage of OM maturity in surface sediments of the Shtokman GCF attests to hydrocarbons migration from subsurface strata.

CYFRA 21.1 in the diagnosis of differents cancer types

The analysis of both the mineralogical and geochemical composition and the stratigraphy of Holocene sediments of Lake Onego provided a novel interpretation of their genesis. Their mineral composition suggests that Holocene bottom sediments generally inherit the composition of terrigenous material that enters the lake with river runoff. The predominant authigenic minerals include biogenic opal from diatom skeletons, Fe-illite, and Fe-chlorite, which are the main iron mineral forms in bottom sediments of Lake Onego. Unstable suspension components (illite and chlorite) transform into their ferruginous varieties under humid climate conditions and high concentrations of iron and silicon in the lake waters. Both the presence of ferromanganese nodules in the uppermost part of bottom sediments of Lake Onego and their formation result from the location of the lake in the northern humid zone, geological composition of Fennoscandian crystalline rocks on the Lake Onego watershed, and the presence of an oxidative geochemical barrier into the lake sediment sequence. Late Holocene bottom sediments are represented by two types of sequences: 1) Fe-Mn enriched layers are formed near the sediment-water interface under oxygenated near bottom waters, and 2) such layers are not formed due to low concentrations of oxygen in water; but there are also non-laminated, homogeneous greyish-green silts, similar to those present in the lower parts of the first type of cores. Sedimentation rates (~0.10 cm y−1) were determined by 210Pb- and 137Cs geochronologies.

Recent environmental changes of Al-Salam Lagoon as inferred from core sediment geochemistry and benthic foraminifera, Jeddah City, Saudi Arabia

The Al-Salam Lagoon is located at the center of Jeddah’s coast, showing unhealthy conditions such as evolving bad odor and spread of a thick sludge layer on its beach. The succession of its recent bottom sediments at the upper intertidal area was investigated through a sediment core SALAM1 (220 cm long) in order to evaluate the impact of pollution on the Al-Salam Lagoon’s environment, comparing with the conditions that existed prior to the industrial revolution. The principal component analysis and variations of benthic foraminifera in the core divided the recent bottom sediments of the lagoon into three intervals. The basal interval (below 110 cm) composed of low organic carbon, high carbonate, white-grey, bioclastic sandy mud enriched in oligotrophic, clear water, hypersaline symbiont-bearing species indicating deposition under unpolluted, natural lagoonal conditions with clear, high salinity waters. The middle interval (45 cm thick) showed a very rapid environmental change with deposition under unpolluted, natural lagoonal conditions as well but in a normal Red Sea salinity water due to a rapid overturn as evidenced by the decrease of hypersaline symbiont-bearing species. The upper interval (65 cm thick) composed of organic-rich, low-carbonate, reduced, black, sludgy mud indicating high anthropogenic activities. This black mud is devoid of benthic life except only two stress (pollution)-tolerant species, suggesting that the upper Al-Salam Lagoon is in its final stage of pollution.

Mineral and geochemical composition of the Onega Ice Lake sediments

An analysis of the mineral-geochemical composition and structure of the Holocene–Pleistocene bottom sediments was performed on Lake Polevskoye, a small lake in the northern Lake Onega area in Russian Karelia, which is considered representative to describe the Late Weichselian Onega Ice Lake sediments. The analysis was accomplished using modern analytical methods, including scanning electron microscopy and ICP-MS, which allowed us to interpret their genesis in a new light. It is assumed that the distribution of rare earth elements (REE) in the bottom sediments of the recent Lake Onega and in the sediments of Onega Ice Lake will improve our understanding of the history of sedimentogenesis. It is apparent in the distribution of REE, their composition and data on the geochemical and mineral composition of the Holocene bottom sediments of Lake Onega and Lake Polevskoye (varved clays) that in their composition of terrigenous matter the material introduced from the north-western part of the catchment area is mainly composed of Archaean and Early Proterozoic crystalline complexes. However, the values of several indicator ratios of elements in the lower part of the of varved clays with shungite interlayers indicate the presence of mixing of clastic material from two sources of different geochemical origin: the north-western part of the catchment area (source of shungite rocks) and the south-eastern part of the catchment area (Phanerozoic sedimentary rocks of the Russian Platform).

Environmental Research and Geochemical Evaluation of Recent Bottom Sea Sediments North and North –East of Lesvos Island, Greece

An environmental and geochemical investigation of 33 surficial sediments of the continental shelf north and north east of Lesvos Island Greece was undertaken to study the mineralogy and geochemistry of the sediments and understand the distribution and sources of various major and trace elements. Texturally all the sediments contain high amounts of mud and clay indicating a uniform facies at depths between 30m - 300m. The sediments are a mixture of terrigenous components (albite, K-feldspar, muscovite, quartz, illite, amphibole and biogenic components (calcite, Mgcalcite, aragonite). Pyrite and glauconite are ascribed to diagenesis. There are four distinctive groups of elements each of which includes related elements, derived from different natural sources on land or in the marine basin. The first group (Ca, Sr) reflects the biogenous carbonate fraction and is negatively correlated against every other element determined. A second (Si, Al, Fe, Na, K, Ti, Ba and Zr) group reflects the aluminosilicate minerals derived from the alteration of volcanic rocks, and a third group (Mg, Ni, Cr, C and Zn) reflects the aluminosilicate minerals derived from the alteration of ultrabasic rocks (peridotites) and the organic carbon. The group of Fe, Mn, Zn and Y is a diagenetic association reflecting the distribution of these elements with pyrite. The association of Cu with Zn reflects a mineralization control in the sediment area. Finally, La and Ce are associated with the K-bearing minerals, while P is related to K and Fe-finegrained minerals. The concentrations of heavy metals in the sediments are normal comparing to the contents of other AEGEAN SEA sediments and are due to natural lithogenic sources.

Hydrogeochemical features of pore-waters of bottom sediments of the shelf and limans of the Northwestern Black Sea region

The article presents information on the chemical composition and salinity of pore-waters of the Holocene bottom sediments in the shelf and limans from the Northwestern Black Sea region. The specific features of the water quality distribution laterally and in depth are considered. The peculiarities of the structure of hydrogeochemical sections confirm the transgressive-regressive character of the sea level change. Analysis of the geological structure, hydrogeochemical and paleoclimatic features allowed to substantiate the hypothesis of the use of limans as sources of salt in the Holocene period. Based on the information on the hydrochemical features of bottom sediments and changes in sea level, the reconstructions of paleogeographic sedimentation environments during the late Pleistocene-Holocene time on the northwestern shelf and limans of the Black Sea are presented.

Modern Bottom Sediments of Lake Onega: Structure, Mineralogical Composition, and Systematization of Rare-Earth Elements

The results of studying the structure and mineral composition of the Upper Holocene bottom sediments of Lake Onega are presented. It is established that there are two types of columns of bottom sediments, for which stratification of layers and formation of Fe–Mn crusts are determined by the diagenesis processes occurring under physicochemical conditions of sediment accumulation according to two scenarios. The distribution spectra of rare-earth elements (REEs) are different in the indicated types of columns, which is apparently attributed to the differences in the oxidation–reduction conditions at the water–sediment interface during the formation of REEs and possibly to the influence of hydrothermal processes.

Contribution of natural and anthropogenic effects in the Iznik Lake bottom sediment: Geochemical and microfauna assemblages evidence

The relationship between the distribution of benthic foraminifera with ostracoda and sediment type and geochemical environment in the Iznik Lake is discussed. The microfauna (benthic foraminifer and ostracod) were sampled in seven recent bottom sediment samples, and geochemical variables of the sediment of the same samples were measured. This study is aimed at investigating the geochemical properties of 7 bottom sediment samples analysed in 5 lines in Iznik Lake. The depths for the samples varies from 1 to 68 m. The microfauna individuals were found in very low quantity, a total of 5 species foraminifera and 11 species 10 genus ostracod were identified. The geochemical properties were found to correspond well to the sediment type and depositional environment and five different sediment/depositional environment types could be distinguished. The individuals of microfauna reveals specific faunal assemblages that are closely related to these sediment and geochemical environment types. According to the survey, sediments encountered in the formation of gypsum crystals feature when considered together with the magnetism of Iznik Lake and the surrounding area suggest that are affected by new tectonics. Again this geochemical study the magnetic properties of the heavy-mineral contents, the entire amount of magnetite and hematite and heavy-mineral content has appeared to be affected by changes in the process. The purpose of this work is to distinguish the natural (geogenic) component, originated by techtonical origin this lake, from anthropogenic contamination owing to human activity. There were relationship between microfauna assemblages and heavy metals, trace element pollutant in the bottom lake sediments. Additionally, less individuals are found in most of the sediment samples in observed (in this 7 samples), this coincidence suggests that the heavy metals within the environment can also be a cause. The reason that of heavy metals, trace element pollutants are a factor in the distribution of microfaunal assemblages of genera and species were observed.

Impact of copper sulfate application at an urban Brazilian reservoir: A geostatistical and ecotoxicological approach

A landscape ecotoxicology approach was used to assess the spatial distribution of copper in the recent bottom sediment (surficial sediment) of a Brazilian subtropical reservoir (the Guarapiranga reservoir) and its potential ecotoxicological impacts on the reservoir ecosystem and the local society. We discuss the policies and procedures that have been employed for the management of this reservoir over the past four decades. Spatial heterogeneity in the reservoir was evaluated by means of sampling design and statistical analysis based on kriging spatial interpolation. The sediment copper concentrations have been converted into qualitative categories in order to interpret the reservoir quality and the impacts of management policies. This conversion followed the Canadian Water Framework Directive (WFD) ecotoxicological concentration levels approach, employing sediment quality guidelines (SQGs). The SQG values were applied as the copper concentration thresholds for quantitative-qualitative conversion of data for the surficial sediment of the Guarapiranga. The SQGs used were as follows: a) interim sediment quality guideline (ISQG), b) probable effect level (PEL), and c) regional reference value (RRV). The quantitative results showed that the spatial distribution of copper in the recent bottom sediment reflected the reservoir's management policy and the copper application protocol, and that the copper concentrations varied considerably, ranging from virtually-zero to in excess of 3gcopper/kgds. The qualitative results demonstrated that the recent bottom sediment was predominantly in a bad or very bad condition, and could therefore have impacts on the local society and the ecosystem. It could be concluded that the management policy for this reservoir was mainly determined by the desire to minimize short-term costs, disregarding long-term socioeconomic and environmental consequences.

Occurrence forms of trace metals in recent bottom sediments from the White and Barents Seas

For the first time based on determination of the geochemical occurrence forms of trace metals the main processes that control the accumulation of elements (Al, Mn, Fe, Mo, Cr, Ni, Co, Cu, Pb, Cd, and As) in the recent sediment cores from the White Sea and Barents Sea were quantified. A high-resolution study of the bottom sediment cores allowed us to estimate the short-term variations (periodicity of 10–15 years) in the accumulation of metals to reveal the periods of maximum Fe and Mn contents in the amorphous hydroxides fraction, which serve as effective adsorbents of the trace elements majority, including heavy metals. The Mn/Fe ratio in the amorphous hydroxides phase can be considered as geochemical indicators of early diagenesis.