Sediment Formation During the Holocene in the Aiviekste Oxbow in the Area of the Abora I Settlement

Introduction. Grain motion in the process of pulp sedimentation in a radial thickener was studied to use the typical links of the automatic control system. Research objective is to explore the possibility of describing the sedimentation process by means of typical links of the automatic control theory based on the physics of grain motion in a radial thickener and the equation of grain motion under laminar and turbulent flow conditions. Methods of research. Stokes’ law that determines the drag force resisting a solid sphere when it slowly moves forward in an unbounded viscous fluid (laminar motion) and the Newton– Rittinger law for the turbulent motion of grain formed the basis of the mathematical model, making it possible to develop a program that chooses a particular equation to calculate the grain sedimentation time in accordance with the grain size. The equations helped to obtain the sedimentation time and hence the time taken to reach the thickener’s bottom, which, in their turn, together with the fractional composition, determine the performance of the thickener. Transition curves were thereby obtained for various granulometric composition, percentage of ore in the pulp, thickener height, ore and pulp density. In the future, this made it possible to approximate the process of sediment accumulation by the equations of one or two lag blocks of the automatic control system. Research results. A computer program has been used that describes the process of sediment accumulation in a thickener, considering the granulometric composition as well as pulp and ore grain density. The program showed that the process of sediment accumulation in a thickener can be described with fair accuracy by a first-order lag block for laminar or turbulent grain motion. For a mixture of coarse and fine fractions, ore sedimentation can be approximated by two parallel lag blocks. Conclusions. Sedimentation process approximation by lag blocks, obtained with fair accuracy, can be used when analyzing, designing and adjusting sedimentation automatic control systems.

AEC experiments for testing the effectiveness of decoupling provided a further opportunity to investigate techniques which an inspection team might use to locate a clandestine nuclear explosion. The investigation consisted of aerial- photographic interpretation, geologic mapping, and on-site examination, both surface and underground. The effects of a series of l1 shots were documented; characteristics of anomalous activity were determined. and evidence of human activity and other clues were tabulated. Results of the investigation indicate that detecting and locating a clandestine undenground explosion in an environment similar to the Winnfield salt dome would be difficult. The detection problem was highlighted by experiments conducted by LRL which proved that the seismic signal from an underground detonation can be substantially reduced by decoupling methods. Thus it is conceivable that the seismic signal from a clandestine decoupled test- might not be noted in an inspection control system, especially in an area where seismic signals from natural causes are common. However, if a seismic signal from any of the COWBOY test shots had been detected, locating the site of the event would have been possible; the chance of success would have decreased as the evidence of anomalous on-site human activity was eliminated. This research emphasizedmore » the necessity that an inspection team be cognizant of the geologic environment and seismic history of the area under its surveillance and that the team be extra-sensitive to any anomalous activity. (auth)« less

Sediment cores were retrieved from 12 lakes in the southern Uinta Mountains ranging in elevation from 2960 to 3475 m. Organic content was determined by loss-on-ignition (LOI) at 1-cm intervals (n = 2850), corresponding to 20 to ∼100 yrs per sample. This data set was used to explore relationships between watershed variables and LOI records. Average LOI values are strongly correlated with lake elevation, elevation of the watershed, extent of late-lying snow and bare rock in the watershed, and the area of upstream lakes. Average LOI values are not significantly correlated with lake depth, or with lake or watershed area. The 12 LOI records can be visually divided into 3 groups with contrasting patterns: Steady, Trending, and Rising. Steady lakes have the lowest average LOI values, and are located in watersheds with the highest maximum elevations and the largest area of upstream lakes and late-lying snow. The most significant determinant on average LOI and LOI pattern is hydrologic through-flow as revealed by the configuration and number of inlets and outlets. The repetition of Steady, Trending, and Rising LOI patterns in different parts of the range, combined with contrasting LOI patterns in adjacent lakes, suggests that watershed characteristics strongly influence organic sedimentation.

Simulating natural hydrate formation and accumulation in sediments from dissolved methane using a large three-dimensional simulator

Faunal characteristics and sediment accumulation processes in the James River estuary, Virginia

Abstract. The Arbreda Cave provides a detailed archaeological record of the Middle to Upper Palaeolithic and is a key site for studying human occupation and cultural transitions in NE Iberia. Recently, studies of lake archives and archaeological sites presented new evidence on climate changes in NE Iberia correlating with Heinrich events. It, therefore, needs to be determined whether climate signals can be identified in the cave sequence of Arbreda, and if so, whether these signals can be correlated with stratigraphic indicators suggesting the continuity or discontinuity of human occupation. We conducted a high-resolution sedimentological and geochemical study, including micromorphological investigations, to shed light on stratigraphy, processes of sediment accumulation and post-depositional alteration in the cave. Seven major sediment units were distinguished which partly correlate with archaeological levels. The lower part of the sequence including Mousterian levels J and K consists of fluvial deposits truncated by a sharp erosional disconformity between Mousterian levels J and I. Strong enrichment with phosphorus and strontium reflect zoogenic inputs. The transition from Mousterian to Archaic Aurignacian in levels I and H, respectively, is reflected by more gradual changes in colour, grain size and geochemical composition. However, a peak in potentially wind-blown particles (40–125 μm in diameter) reflects higher aeolian input, and banded microstructure suggests reworking of sediments at the interface. Both properties correlate with low density of finds suggesting low intensity of human occupation related to a dry spell. More arid conditions than during the Holocene are indicated for the Gravettian to Solutrean levels. These findings are in agreement with previous palaeoclimatic interpretations as based on palaeontological proxies. The detailed multi-proxy analyses of the sequence adds to our understanding on sediment accumulation and alteration in the Arbreda Cave. The transition from the Middle to Upper Palaeolithic probably includes a gap in human occupation. Assessing the significance and duration of this gap and correlating the climate signal requires three-dimensional reconstructions of find densities and more reliable geochronological control.

Accumulation rates and 137Cs distribution in sediments off the Po River delta and the Emilia-Romagna coast (northwestern Adriatic Sea, Italy)

Changes in the surface area of lakes can indicate climate change and human activity, and there are few reports on the characteristics of such changes in North Xinjiang, China. The normalized difference water index (NDWI) was modified by using the middle infrared band (MIR) instead of the near infrared band (NIR). The modified NDWI (MNDWI) can effectively extract the lake boundary. Changes in the number and area of lakes (surface area > 1 km2) were examined using topographic maps (1:100,000) and Land Remote-Sensing Satellite (System, Landsat) series images (multispectral scanner, thematic mapper, enhanced thematic mapper plus, and operational land imager) for the period from 1960 to 2018. The results showed that more than 85.00% of the lakes were identified in the Erqis River Basin (ErRB), Ulungur River Basin (URB), and Central North Tianshan (CNT) between 1960 and 1980, few lakes were observed in the Ebinur Lake Basin (ELB), Jimunai River Basin (JRB), Emin River Basin (EmRB), Guerbantonggute Desert Area (GDA), and Ili River Basin (IRB), and no lakes were observed in the Eastern North Tianshan (ENT). The surface area and numbers of lakes in North Xinjiang were increased by 795.99 km2 (35.54%) and 39 (195.00%), respectively, between 1960 and 2018. Multiple factors influenced the changes observed for different types of lakes. The number and surface area of mountain lakes fluctuated and increased mainly in response to precipitation and temperature. The number of oasis lakes remained unchanged until 1990, but then increased in response to precipitation and temperature. The fluctuations in the surface area of oasis lakes, which were affected by climate and groundwater development, were relatively small between 1960 and 1990, but then became larger. However, the number and surface area of plain lakes increased between 1960 and 2018 and were mainly influenced by climate change and human activity, such as water diversion for irrigation, ecological restoration projects, and the implementation of the river chief system.

It is just over sixty years since Stuart Piggott published his major work, Neolithic Cultures of the British Isles. This was the first comprehensive account of what was then known and assumed about the ‘New Stone Age’ in these islands, and it surveyed discoveries and summarized debates that had occurred over the previous century. This process of gradual accumulation of data and ideas has continued apace since Piggott was writing, not least owing to the precision with which we can now date much of the activity that characterizes the Neolithic. When Piggott was writing his book in the early 1950s an American, Willard Libby, was experimenting with the technique of radiocarbon dating as a by-product of the development of nuclear technology. This dating method uses the rate of decay of radioactive isotopes to measure the time that has elapsed since a sample of organic matter last exchanged carbon with its environment—in short, the time since an organism died. Application of the method has cumulatively transformed our understanding of prehistoric chronology. To illustrate the impact upon the study of Neolithic Britain, we have only to appreciate that in Neolithic Cultures Piggott imagined a British Neolithic period that lasted for around five hundred years, beginning in about 2000BCE. This estimated span was based on a series of assumptions about the rate of cultural change, and the affinities between artefacts in Britain, continental Europe, and further afield. However, over the past half-century this inherited chronology has been swept away as radiometric dating has gradually been refined, and huge numbers of dated samples have accumulated. These now suggest that the Neolithic period began in Britain shortly before 4000 BCE, and ‘ended’ with the advent of a variety of objects made of metal instead of stone, from around 2400 BCE. The implications of this transformed appreciation of the duration of the Neolithic are profound, for while Piggott and his contemporaries were dealing with periods of historical time that were comparable with those with which we are familiar from recorded history (the rise and fall of the Roman Empire, the emergence and spread of Islam, the development of capitalism), we now have evidence for human activity in the Neolithic of Britain that is dispersed across an expanse of time as much as three times longer than these major historical episodes.

This paper is a second report on the linkage between lake bottom dynamics and lake morphometry. The areal distribution of erosion and transportation (aE+T) or accumulation (aA = 100 − aE+T) processes at lake bottoms is suggested to be governed by (1) an energy factor E = ( √a/Dmax), where a is the lake area in square kilometers and Dmax is the maximum depth in meters, (2) a slope factor S = 41 exp(0.061 D¯/√a), where D¯ is the mean depth in meters, and (3) a form factor, Vd−l = Dmax/3D¯. This relationship may be given as aE+T = 100 − aA = 25 (√a/D¯) 41 exp 0.061 D¯/√/a) where aE+T is the percentage area of lake bed subject to processes of erosion and transportation. The ratio √a/D¯ is called the dynamic ratio (DR). This formula is physically more sound than an earlier model and more accurate when applied on the available empirical data from nine Swedish lakes. It also reveals new aspects of the relationship between bottom dynamics and lake morphometry. The formula may be useful since it provides a means by which to estimate the percentage of a given lake area that is dominated by erosion and transportation processes (aE+T) or accumulation processes (aA) from only two morphometric standard parameters: lake area a and mean depth D¯.

If your undergraduate experience in stratigraphy was anything like mine, it was overwhelmingly dull. It was all about nomenclature and classification and endless lists of formation names. There were apparently no questions to be asked and the goal of stratigraphy was to devise boxes into which to place all types of geologic data. Notwithstanding the important work of correlation, the perception was that it was the sedimentologists who did the real science, science that focused on the processes of sediment accumulation and their controlling factors. Since then, stratigraphy has undergone a conceptual revolution, and it is necessary to examine how the field has changed and what those advances mean for paleobiology.

Field studies at Mueller and Tasman Glaciers in New Zealand and in Iceland have revealed extensive ice-marginal moraine sequences fed by a series of debris bands containing characteristic rounded debris. We interpret these debris bands as meltwater deposits from relict conduits. The process of sediment accumulation described requires that debris undergoing basal or high-level ice transport is entrained by running water, becoming comminuted and rounded before being returned to high-level ice transport and eventual deposition in marginal moraines. Tins sequence of events suggests a link between glacier hydrology and ice-marginal sedimentation, possible mechanisms for which are explored. Pronounced moraines with rounded debris can be expected if (a) large quantity of debris is carried within the englacial drainage network; (b) there is a tendency for this debris to be abandoned within the ice; and (c) ice-flow trajectories and ablation ensure that this debris congregates at the ice surface. Streams which flow at high level within the ice can intercept and entrain englacial debris derived from rock fall. However, debris sources at Gigjökull and Steinholtsjökull in Iceland are restricted to the glacier bed, suggesting that, in certain cases, the presence of a basal overdeepening acts as a key factor controlling the accumulation of these moraines. Water pressure rises as channels encounter an overdeepening, forcing debris-laden streams to leave the bed and take an englacial route. That debris may pass from ice to water and back into ice before deposition has gone largely unrecognised in accounts of glacial process systems, yet it provides an explanation of how temperate alpine glaciers can include water-worked debris in their marginal depositional facies.

Field studies at Mueller and Tasman Glaciers in New Zealand and in Iceland have revealed extensive ice-marginal moraine sequences fed by a series of debris bands containing characteristic rounded debris. We interpret these debris bands as meltwater deposits from relict conduits. The process of sediment accumulation described requires that debris undergoing basal or high-level ice transport is entrained by running water, becoming comminuted and rounded before being returned to high-level ice transport and eventual deposition in marginal moraines. Tins sequence of events suggests a link between glacier hydrology and ice-marginal sedimentation, possible mechanisms for which are explored. Pronounced moraines with rounded debris can be expected if (a) large quantity of debris is carried within the englacial drainage network; (b) there is a tendency for this debris to be abandoned within the ice; and (c) ice-flow trajectories and ablation ensure that this debris congregates at the ice surface. Streams which flow at high level within the ice can intercept and entrain englacial debris derived from rock fall. However, debris sources at Gigjökull and Steinholtsjökull in Iceland are restricted to the glacier bed, suggesting that, in certain cases, the presence of a basal overdeepening acts as a key factor controlling the accumulation of these moraines. Water pressure rises as channels encounter an overdeepening, forcing debris-laden streams to leave the bed and take an englacial route. That debris may pass from ice to water and back into ice before deposition has gone largely unrecognised in accounts of glacial process systems, yet it provides an explanation of how temperate alpine glaciers can include water-worked debris in their marginal depositional facies.

This study offers new insights into the internal architecture of shallow marine carbonate sediments deposited in an epeiric sea formed on a broadly flooded passive margin continental shelf. The Ullayah Member of the Late Jurassic Hanifa Formation is exposed along the Tuwaiq Mountain Escarpment in Central Saudi Arabia and serves as an example. High‐resolution drone imagery over a 4 × 4 km2 wadi system, measured‐sections and thin‐section petrography are utilized to develop the three‐dimensional architecture of the lagoonal sediments deposited in an inner‐ramp setting. Parasequence sets have been mapped on the digital outcrop models that demonstrate a high degree of lateral and vertical thickness variability associated with stromatoporoid/coral buildups and inter‐buildup sediments. The stromatoporoid/coral buildups have been interpreted to be deposited during the late Transgressive Systems Tract and Highstand System Tract. The positive relief developed by the stromatoporoid/coral buildups resulted in hydrodynamic acceleration of currents in the inter‐buildup areas, which limited sediment deposition. The incomplete filling of the inter‐buildup areas led to an undulating topography, which significantly influenced depositional architecture in the next parasequence set. This theme of sediment filling, also referred to as compensational stacking, was repeated over the next two parasequence sets, with an overall decreasing accommodation towards the late highstand, eventually levelling the uneven topography at the top of the Ullayah Member. The study offers insights into the processes of sediment accumulation in an inner ramp lagoon and/or on a flat‐top shallow marine epeiric carbonate shelf. Although accumulation is cyclic, neither strict facies patterns nor uniform cycle thicknesses can be discerned on a kilometre scale. This insight potentially provides a reason for the frequently debated correlation of cycles and facies patterns in carbonate sequences in shallow epeiric seas.

The impact of floods on the migration activity of elements coming from urbanized territories to the Amur river was assessed. The influence of large cities on pollution of water and floodplain ecosystems is revealed. The content of heavy metals in water, bottom sediments, and small watercourses draining urban areas is characterized. The processes of sediment accumulation in the floodplain, their influence on the redistribution of elements and geochemical transformations in the soil space of floodplain soils are studied. Conditions for the accumulation of heavy metals in soils are described, their concentration levels and migration activity are determined. The role of organic matter in swamps and silts on water pollution and bottom sediments of the Amur river is shown. It was found that the main mass transfer of soluble substances and pollutants dispersed fractions of nailc is carried out by water flow during floods.