Changes In Source Material Research Articles

Environmental changes in southeastern Europe over the last 450 ka: Magnetic and pedologic study of a loess-paleosol profile from Kaolinovo (Bulgaria)

Magnetic properties are sensitive paleoenvironmental proxies frequently used in studies of loess paleosol profiles. Understanding precisely the magnetic recording of soil responses to environmental and climatic changes needs combining pedologic data and geophysical proxies. Here we present a new high-resolution study of a 450 ka old loess-paleosol profile from low Danube loess area at Kaolinovo (NE Bulgaria). The profile consists of Holocene soil S0 on top, three paleosol units (S1, S2, S3–S4) and the intercalated loess horizons L1 to L4. Mineral magnetic and rock magnetic data together with pedological parameters (particle size distribution, total, crystalline and amorphous iron, soil organic carbon, total nitrogen, cation exchange capacity, carbonate content) show systematic variations in response to environmental changes. Principal component analyses carried out separately on magnetic mineralogy, rock magnetic and pedological variables reveal the complex response of loess – paleosol sediments to changes in source material and climate. The observed sharp shift in coercivity of mineral magnetic carriers at depth of the third loess L3 marks the change from low-coercivity mineral assemblages in older units to higher coercivity in the last three loess paleosol couplets (L1-S0, L2-S1, L3 – S2). This boundary is related to both dust source change and increased climate aridity. The observed spikes in concentration-dependent magnetic parameters in the lowermost part of the profile and particular magnetic and pedologic signature of the oldest deposits (S3–S4 pedocomplex) suggest that it may result from tephra additions in the studied loess-paleosol sequence, tentatively correlated to cryptotephra layers in other terrestrial archives in the region like Tenaghi Philippon and lake Ohrid sedimentary sequences. This work demonstrated that using PCA tool for studying the significance and objective inter-relationships of multiple mineralogical, mineral magnetic and pedological characteristics along depth of loess – paleosol profiles is an exemplary approach for revealing the underlying sedimentary and environmental processes.

Noise behavior and reliability analysis of non-uniform body tunnel FET with dual material source

In this paper the noise analysis of Non-Uniform Body TFET with Dual Material Source is performed incepting both the absence and presence of different types of trap charges when the device undergoes various changes in source material (like Si, Ge, and both Si + Ge), and temperature (200 K–400 K) etc. In this study it has been found that the value of drain current noise power spectral density (Sid) for the device is 9.92 × 10−23 A2/Hz and for entire source region having Si and Ge materials the Sid values are estimated as 3.3 × 10−24 A2/Hz and 1.7 × 10−19 A2/Hz, respectively. In the device noise degradation effect is admissible when different performance parameters are accounted as compared to the cases when source material is completely made of Si or Ge. The aforesaid fact has been validated by normalized Sid (Sid/Ids2) vs. Drain current (Id) and Sid (Sid/Ids2) vs. Subthreshold Swing (SS) plot analysis, which clearly indicates the less effect of noise and superior electrostatic coupling in the device. Furthermore, the systematic study for effect of different types of noise under various trap charge distributions is also reported which showed that the device is negligibly effected by donor trap charges. Lastly to explore the reliability part of the device the temperature analysis including the absence and presence of trap charges for the noise behavior illustrated that the effect of increase in noise due to presence of trap charges is more at low temperatures and low gate to source voltages (Vgs) and the dominating noise component is found to be G-R noise.

Thermal tuning of arsenic selenide glass thin films and devices.

We present a method of post-deposition tuning of the optical properties of thin film dielectric filters and mirrors containing chalcogenide glass (ChG) layers by thermally adjusting their refractive index. A common challenge associated with the use of ChG films in practical applications is that they suffer from slight run-to-run variations in optical properties resulting from hard-to-control changes in source material and deposition conditions. These variations lead to inconsistencies in optical constants, making the fabrication of devices with prescribed optical properties challenging. In this paper, we present new work that takes advantage of the large variation of a ChG films' refractive index as a function of annealing. We have carried out extensive characterization of the thermal index tuning and thickness change of arsenic selenide (As2Se3) ChG thin films and observed refractive index changes larger than 0.1 in some cases. We show results for refractive index as a function of annealing time and temperature and propose a model to describe this behavior based on bond rearrangement. We apply thermal refractive index tuning to permanently shift the resonance of a Fabry-Perot filter and the cutoff wavelength of a Bragg reflector. The Bragg reflector, consisting of alternating As2Se3 and CaF2 layers, exhibits high reflectance across a ∼550 nm band with only five layers. Modeling results are compared with spectroscopic measurements, demonstrating good agreement.

Influences of forested and grassland vegetation on late Quaternary ecosystem development as recorded in lacustrine sediments

AbstractGeosphere-biosphere interactions are ubiquitous features of the Earth surface, yet the development of interactions between newly exposed lithologic surfaces and colonizing plants during primary succession after glaciation are lacking temporal detail. To assess the nature, rate, and magnitude of vegetation influence on parent material and sediment delivery, we analyzed ecosystem and geochemical proxies from lacustrine sediment cores at a grassland site and a forested site in the northern United States. Over time, terrigenous inputs declined at both sites, with increasing amounts of organic inputs toward present. The similarities between sites were striking given that the grassland sequence began in the Early Holocene, and the forested sequence began after the last glacial maximum. Multiple mechanisms of chemical weathering, hydrologic transport, and changes in source material potentially contribute to this pattern. Although there were strong links between vegetation composition and nitrogen cycling at each site, it appears that changes in forest type, or from oak woodland to grassland, did not exert a large influence on elemental (K, Ti, Si, Ca, Fe, Mn, and S) abundance in the sedimentary sequences. Rather, other factors in the catchment-lake system determined the temporal sequence of elemental abundance.

Identifying the source of fluvial terrace deposits using XRF scanning and Canonical Discriminant Analysis: A case study of the Chihshang terraces, eastern Taiwan

The source of fluvial deposits in terraces provides important information about the catchment fluvial processes and landform evolution. In this study, we propose a novel approach that combines high-resolution Itrax-XRF scanning and Canonical Discriminant Analysis (CDA) to identify the source of fine-grained fluvial terrace deposits. We apply this approach to a group of terraces that are located on the hanging wall of the Chihshang Fault in eastern Taiwan with two possible sources, the Coastal Range on the east and the Central Range on the west. Our results of standard samples from the two potential sources show distinct ranges of canonical variables, which provided a better separation ability than individual chemical elements. We then tested the possibility of using this approach by applying it to several samples with known sediment sources and obtain positive results. Applying this same approach to the fine-grained sediments in Chihshang terraces indicates that they are mostly composed of Coastal Range material but also contain some inputs from the Central Range. In two lowest terraces T1 and T2, the fine-grained deposits show significant Central Range component. For terrace T4, the results show less Central Range input and a trend of decreasing Central Range influences up section. The Coastal Range material becomes dominant in the two highest terraces T7 and T10. Sediments in terrace T5 appear to have been potentially altered by post-deposition chemical alteration processes and are not included in the analysis. Our results show that the change in source material in the terraces deposits was relatively gradual rather than the sharp changes suggested by the composition of the gravels and conglomerates. We suggest that this change in sources is related to the change in dominant fluvial processes that controlled by the tectonic activity.

Relocation of the Yellow River estuary in 1855 AD recorded in the sediment core from the northern Yellow Sea

Relocation of the Yellow River estuary has significant impacts on not only terrestrial environment and human activities, but also sedimentary and ecological environments in coastal seas. The responses of regional geochemical characteristics to the relocation event, however, have not been well studied. In the present study, we performed detailed geochemical elemental analyses of a sediment core from the northern Yellow Sea and studied their geochemical responses to the 1855 AD relocation of the Yellow River estuary. The results show that TOC/TN, Co/Al2O3, Cr/Al2O3, Ni/Al2O3 and Se/Al2O3 ratios all decreased abruptly after 1855 AD, and similar decreases are observed in the sediments of the mud area southwest off the Cheju Island. These abrupt changes are very likely caused by the changes in source materials due to the relocation of the Yellow River estuary from the southern Yellow Sea to the Bohai Sea, which the corresponding decreasing trends caused by the changes in main source materials from those transported by the Liaohe River, the Haihe River and the Luanhe River to those by the Yellow River. Because the events have precise ages recorded in historical archives, these obvious changes in elemental geochemistry of sediments can be used to calibrate age models of related coastal sea sediments.

Rapid identification of source material levels in coral sand ornithogenic sediments by reflectance spectroscopy

Ornithogenic sediments are ideal materials for studying past eco-environmental changes. We collected sediment cores from Xisha archipelago of the South China Sea. The relative ratios of source materials (plant, guano and coral sand) of such sediments from Guangjin, Jinqing, Jinyin and Ganquan Islands in the Xisha archipelago, were reconstructed by reflectance spectroscopy. The consistence between the results obtained from reflectance spectroscopy and those obtained from traditional chemical analysis suggests that reflectance spectroscopy can be an ideal indicator for source material levels in the ornithogenic coral sand sediments. The possible implications of changes in source materials from the bottom toward top of the sediment cores are also discussed in our study. Seabird activities appear central to the ecological development of these island ecosystems.

Zeitgeschichte im digitalen Zeitalter. Neue und alte Herausforderungen

Vorspann Wer archiviert die SMS von Angela Merkel? Was geschieht mit dem E-Mail-Verkehr großer Unternehmen? Die Zeitgeschichte steht im digitalen Zeitalter vor vielen solchen Fragen und Herausforderungen. Die Quellen und nicht zuletzt ihre Verfügbarkeit ändern sich, neue methodische Zugriffe sind unabweisbar, ohne dass alte ihre Bedeutung verlieren. Die Zeitgeschichte steht vor einer Zeitenwende – und merkt es nicht, so der in Maastricht lehrende Historiker Kiran Klaus Patel in seinem Plädoyer für eine umfassende Debatte über die Grundlagen der Zeitgeschichte.

Assessing the recent (1834 – 2002) morphological evolution of a rapidly prograding delta within a GIS framework: Macquarie Rivulet delta, Lake Illawarra, New South Wales

The recent morphological evolution of Macquarie Rivulet delta, Lake Illawarra, New South Wales, has been assessed from historical parish maps from 1834, 1892, 1916 and 1927 along with aerial photographs from 1938 to 2002. These images were digitised, georeferenced and analysed in a GIS framework. The 1834 sketch map could not be georeferenced and it was excluded from the calculation of delta progradation areas. Between 1892 and 1927 morphological changes were minimal, probably because the areas were not resurveyed between these map editions. A significant change in morphology between 1927 and 1938 reflects a change in source material from maps to aerial photographs. The research highlights that great care must be taken when utilising historical data. Major morphological changes observed between 1938 and 2002 included the development of a large crevasse splay in the 1960s to 1970s and the abandonment and infilling of the delta's previously active distributary channels. The research shows that the morphological changes observed on the delta can be related to both natural processes and anthropogenic modifications to the catchment and thus could be used in the development of catchment management plans.

Tectonic and climatic control of the changes in the sedimentary record of the Karnali River section (Siwaliks of western Nepal)

Abstract A multidisciplinary study was conducted on the section of the Siwalik Group sediments, approximately 5000 m thick, exposed along the Karnali River. Analysis of facies, clay mineralogy and neodymium isotope compositions revealed significant changes in the sedimentary record, allowing discussion of their tectonic or climatic origin. Two major changes within the sedimentary fill were detected: the change from a meandering to a braided river system at ca 9.5 Ma and the change from a deep sandy braided to a shallow sandy braided river system at ca 6.5 Ma. The 9.5‐Ma change in fluvial style is contemporaneous with an abrupt increase of ɛNd(0) values following a ɛNd(0) minimum. This evolution indicates a change in source material and erosion of Lesser Himalayan rocks within the Karnali catchment basin between 13 and 10 Ma. The tectonic activity along the Ramgarh thrust caused this local exhumation. By changing the proximity and morphology of relief, the forward propagation of the basal detachment to the main boundary thrust was responsible for the high gradient and sediment load required for the development of the braided river system. The change from a deep sandy braided to a shallow sandy braided river system at approximately 6.5 Ma was contemporaneous with a change in clay mineralogy towards smectite‐/kaolinite‐dominant assemblages. As no source rock change and no burial effect are detected at that time, the change in clay mineralogy is interpreted as resulting from differences in environmental conditions. The facies analysis shows abruptly and frequently increasing discharges by 6.5 Ma, and could be linked to an increase in seasonality, induced by intensification of the monsoon climate. The major fluvial changes deciphered along the Karnali section have been recognized from central to western Nepal, although they are diachronous. The change in clay mineralogy towards smectite‐/kaolinite‐rich assemblages and the slight decrease of ɛNd(0) have also been detected in the Bengal Fan sedimentary record, showing the extent and importance of the two major events recorded along the Karnali section.

Cenozoic lithospheric extension induced magmatism in Southwest Japan

Island chains off western Kyushu are the surface exposure in the northern margin of the Taiwan–Sinzi Folded Zone that spreads along the arc–trench system in the back-arc side from SW Japan to Taiwan. Intermittent igneous activity between the Middle Miocene and Holocene occurred on these islands and widely covered or intruded sedimentary rocks of Early–Middle Miocene. Geochemistry of the volcanic rocks from the Hirado, Ikitsuki and Takushima islands believed to relate to the back-arc opening along the East China and Japan Seas shows a temporal change in source material. Submarine to sub-aerial volcanism occurred on Hirado Island at 15 Ma during the final opening stage of the East China Sea producing tholeiitic basalt and associated andesite–dacite. These eruptives show low incompatible element contents and high FeO*/MgO ratios and reflect a tholeiitic differentiation trend. High Sr and Pb and low Nd isotopic ratios suggest the involvement of EM2-like lithospheric mantle and crustal material in the formation of these syn-opening volcanic rocks. Post-opening alkali basalt volcanism occurred at 9–6 Ma on the islands is characterized by OIB-like higher large ionic lithophile elements (LILE) and high field strength elements (HFSE) compared to 15 Ma basalts in this region and Quaternary basalts along the volcanic front. They have variable range of incompatible element concentrations and ratios along with variable Sr, Pb and Nd isotopic ratios suggesting the involvement of both lithospheric and asthenospheric sources at variable melting degrees (from 4% to less than 15%). The observation that the isotopic compositions of Quaternary alkali basalts south of the studied area are even more depleted suggests an increase in the involvement of asthenospheric source with time.

Sediment provenance and dispersal in a deep marine foreland basin: the Lower Carboniferous Culm Basin, Czech Republic

The Lower Carboniferous Culm Basin of the Czech Republic represents the most easterly and southerly part of the European Variscan foreland basin system. The NNE–SSW-trending basin is exposed along the eastern flank of the Bohemian Massif. It contains up to 7.5 km of deep marine sediment deposited as an axial turbidite system sourced from south/southwest of the basin. Heavy mineral data and clast types indicate that for much of the Viséan, sediment was sourced from a predominantly low-grade metamorphic terrane and Viséan limestones. In the latest Viséan, a progressive change in source material is recorded by an increase in high-grade metamorphic detritus. Studies of Variscan nappe pile emplacement along the eastern flank of the Bohemian Massif allow an assessment of the relationship between basin development and nappe emplacement. Basin initiation coincided with underthrusting of high grade metamorphic (Moldanubian) nappes at 340 Ma. Sedimentation was synchronous with nappe emplacement throughout the Viséan which resulted in uplift and erosion of a low grade metamorphic terrane. Moldanubian nappes were exhumed at approximately 330 Ma when high grade metamorphic detritus entered the basin. Two phases of northward-directed sediment progradation are recognized. Sediment progradation is considered to be related to changes in drainage basin size and/or climatic fluctuations within the Variscan Orogen, since sediment is inferred to have been supplied to the basin axially rather than laterally and subsidence curves show no significant change in subsidence rates. In contrast to many models of foreland basin sediment distribution, filling of the Culm Basin was largely independent of tectonic activity adjacent to the basin margin and/or of subsidence rate changes. Sedimentation in the Culm Basin commenced 10–15 Ma earlier than the rest of the Variscan foreland, and records the first impact of the northwardly propagating Variscan Orogen in northern Europe.

Anorogenic metaluminous and peraluminous granite plutonism in the mid-proterozoic of Wisconsin, USA

A magmatic gap from 1.82 to 1.76 b.y. in the Lake Superior region represents the transition from synorogenic calc-alkaline igneous activity of the Penokean Orogeny to anorogenic potassic granophyric granite and ignimbrite. This paper deals with the petrogenetic evolution of 1.76 b.y. granites which represent a major change in source material and conceivably tectonic setting. Although perhaps related to a termination of the Penokean Orogeny by melting of a tectonically thickened crust during collision, these post-Penokean granites may represent the initial appearance of anorogenic, potentially rift-related igneous activity that was widespread throughout North America during late Precambrian time. These post-Penokean granites are too iron-rich and Al-poor to be considered calc-alkaline, a compositional feature shared with most anorogenic igneous activity of continental regions. Within this suite in central and northern Wisconsin, regional differences in composition indicate at least two different granite magma types: one a metaluminous suite of biotite and biotite-hornblende granite and a peraluminous suite of two-mica granite. The systematic compositional differences (Al, Fe/Mg, Ba/Sr, REE) in the two magma suites are likely the result of small differences in residue mineralogy and/or source composition. In general, the degree of fusion was small (10%) and probably of relatively young Penokean material. Both suites have a range of composition due to feldspar dominated fractional crystallization. Removal of the accessory minerals apatite, zircon, and allanite resulted in the REE depletion with differentiation of the two-mica granites. The granites intruded into the upper levels of the crust, and the appearance of primary celadonitic muscovite and subsolvus alkali feldspars (silicic members only) in the two mica granites indicate crystallization at depths of 10–11 km. The biotite granites contain both hypersolvus and subsolvus members and are intruded at depths less than 6 km with the more shallow members generating major volumes of ignimbrite. As a marked departure from the characteristics of most anorogenic granites, these melts crystallized at fairly oxidizing conditions (higher for the two-mica suite) as reflected in the composition of biotite, predominance of magnetite over ilmenite, and early appearance of the Fe-Ti oxides in the crystallization sequence.

Organic geochemistry of Cam Loch (Sutherland) sediments

Because diagenesis of organic matter in post-glacial lacustrine sediments is minimal, organic compounds characteristic of the source organisms should be present in the sediment profile and may constitute indicators of changing environmental conditions during the last 12,000 years. To verify this hypothesis, analysis of six sections from the complete postglacial sediment profile of Cam Loch (Sutherland, Scotland) is reported. The composition of the sterol and n-alkanoic acid fractions is indicative of the relative input from terrestrial and aquatic biota, while the alkane fraction is related to the terrestrial source material and amount of microbial activity. The abundance of branched/cyclic alkanoic and n-alkenoic acids is influenced by the trophic status of the lake. Additional compound classes associated with terrestrial input are methyl n-alkyl ketones, n-alkanols, α,ω-dicarboxylic acids and ω-hydroxyacids. It is shown that these observations provide a record of changes in source material and trophic status complementary to and consistent with the record deduced from the morphological residues and inorganic chemistry of an adjacent site.

THE CLAY MINERALOGY AND SOME TRACE ELEMENT CONTENTS OF THE SPEETON CLAY

Summary Pronounced time-related trends are evident in the clay mineralogy of the Speeton Clay (Lower Cretaceous): the kaolinite/illite ratio decreases consistently as the sediments get younger, and the other main mineral, probably an illitesmectite, becomes progressively more illitic. It is suggested that these changes reflect weathering conditions at the source rather than differences in actual source-rock type or weathering of the Speeton Clay itself. This conclusion is supported by the relative consistency in trace element contents, which might be expected to reflect major changes in source material.

Possible Uses of Clay Minerals in Search for Oil

During the last fifteen to twenty years, our understanding of the geologic significance of the clay minerals has increased from nearly zero to the point where we can begin to make some practical application of our knowledge. Following is a brief list summarizing our general knowledge. 1. We know the clay mineral composition of most of the formations in the United States. 2. Pre-Middle Mississippian clay suites are less complex than those in younger sediments. 3. The composition of clay suites may change drastically over an interval of a few feet or remain nearly constant throughout 5,000 feet of section. 4. Both source and environmental information can be obtained. 5. Expanded clays are contracted by burial. 6. The clay suites in limestones are as variable as those in shales. 7. Clay minerals in sandstones are more apt to have been altered after deposition than the clays in other rocks. 8. Once the clay mineral distribution pattern is established, reasonable environmental identifications can commonly be made. 9. If the environmental significance of the clay suites can be established by other means, the clay data can be used independently to identify environments near the control area. 10. Clays can best be used for environmental determinations in young sediments where deposition is relatively slow and environments are materially different. 11. Clay can be used for approximate time correlation where bentonite beds or unconformities are present and where there is a change in source material. 12. Relatively minor clay differences can be correlated for 10-50 miles. In the Upper Mississippian and Lower Pennsylvanian of the Mid-Continent, the clay suites reflect the source areas and tectonic history. Many formations in this interval contain distinctive clay suites which can be used for identification. Detailed correlations can be made by making detailed studies. Both in recent and ancient sediments (shales, limestones, and sandstones) clay mineral suites are related to depositional environments. Clays should be of value in locating the more effective energy barriers. In the recent, both sandstone bars and limestone reefs appear to act as barriers and cause different clay suites to be deposited on the landward and seaward sides. Environmental studies are best made by investigating the whole basin and determining the distribution pattern of the various clay facies. It has been shown that clays can be used to subdivide formations and to locate formation boundaries more accurately than can be accomplished by other techniques. Regional (1,000-2,000 miles) clay mineral zones occur in the Lower and Middle Ordovician and the Upper Mississippian. In the Ouachitas, kaolinite can be used to differentiate the geosynclinal and foreland facies. The relative sharpness of the X-ray diffraction peak of illite affords a good measure of the degree of metamorphism in this area. The available data suggest that there may be some relation between hydrocarbon production and expanded clay minerals. Most of the major producing formations in the United States contain an abundance of expanded clays (montmorillonite, mixed-layer-illite-montmorillonite, and chlorite-montmorillonite). Expanded clays retain their pore water to greater depths of burial than do the other clays. If hydrocarbons are formed at any appreciable depth, the shales containing expanded clays would be the main source of water to carry the hydrocarbons from the shales. Comparison of clay data and velocity data for Tertiary and Paleozoic shales of similar composition (montmorillonite) indicates that the rate of collapse of the expanded clay layers is related to depth and is independent of time. However, the loss of pore water (as shown by density and velocity data) from shale is closely dependent on time.