bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geochemical characteristics of overbank deposits and their potential for determining suspended sediment provenance; an example from the River Severn, UK
Authors: Bottrill L. J. , Walling D. E. , Leeks G. J. 
Published: April 2008

Abstract

The sources of suspended sediment are an important factor controlling sediment yield and sediment budgets. Sediment provenance is an essential prerequisite for elucidating the overall sediment delivery system. Only a proportion of the suspended sediment transported by a river during floods may reach the river mouth, and lowland floodplains frequently represent important sediment sinks. The geochemical properties of floodplain sediments have been used in stratigraphic studies of long-term environmental changes in river basins, but their potential for investigating recent and contemporary sediment sources has not been fully exploited. This paper reports the results of a study that has used the geochemical properties of overbank deposits, including heavy metal, trace metal and cation exchange elements, to establish the main suspended sediment sources within the 10 000 km
2
basin of the River Severn, UK. The results confirm the importance of the upland catchments of the rivers Teme, Vyrnwy and Upper Severn as sources, providing 70% of sediment in the Basin, and of the River Avon as a source of 27% of the <63 μm material. The catchments of the rivers Perry, Stour and Tern, which drain the central areas of the Severn Basin, are shown to be insignificant sources of sediment, contributing only 0–4% to sediment deposited at Haw Bridge. An attempt was also made to establish historical sediment source contributions, although changes in sediment geochemistry during storage in floodplain sinks cause this to be largely unsuccessful.
Alluvial architecture of the Mississippi valley: predictions using a 3D simulation model
Authors: Bridge John S. 
Published: April 2008

AbstractThe 3D alluvial-architecture model of Mackey & Bridge (1995,Journal of Sedimentary Research,B65, 7–31) is used to simulate the nature of avulsion and alluviation of the Mississippi River in its lower alluvial valley and delta plain during the Holocene period, a time of relative sea-level rise. An important objective of these simulations is to examine the controls on the relative proportion of channel-belt deposits and floodplain deposits within the alluvium. Although the model cannot predict the exact avulsion behaviour of the Mississippi, the timing and location of avulsions are predicted well in a general sense. In the lower Mississippi valley, avulsions commonly originate in an up-valley location near Memphis, and the mean avulsion period is 1000–1500 a. This avulsion frequency, combined with large channel-belt width relative to valley width, has resulted in large channel-deposit proportion along the length of the lower alluvial valley. On the delta plain, the model predicts that avulsions are relatively frequent (intervals of decades to centuries) on active deltas where deposition rate on alluvial ridges is greatest and down-valley slopes are least (related to relative sea-level rise). Avulsions originating from locations on the delta plain more distant from the coast occur at longer time intervals (hundreds to thousands of years), because alluvial-ridge topography develops more slowly in these regions. Such avulsions give rise to discrete delta lobes or subdeltas (e.g. Teche, Lafourche). Channel-deposit proportion is generally low on the delta plain, and decreases towards the Gulf of Mexico. This is primarily due to down-valley increase in floodplain width relative to channel-belt width. However, channel-deposit proportion is locally high near avulsion points. These results indicate that change in alluvial architecture during relative sea-level rise in near-coastal settings is more complicated than suggested by recent sequence-stratigraphic models where the proportion of channel-belt deposits is postulated to be controlled primarily by only two factors: deposition rate and valley width.
The Makapansgat Australopithecine site from a speleological perspective
Authors: Latham Alf G. , Herries Andrew , Quinney Patrick , Sinclair Anthony , Kuykendall Kevin 
Published: April 2008

Abstract

Remains of
Australopithecus africanus
from the Limeworks Cave, Makapansgat, South Africa, are believed to belong mainly to a metre-thick, bone-rich, speleothem layer. The flowstone is one stratum among a sequence of speleothems, muds, silts, sands and fine and coarse breccias, the study of which has evoked some disagreement. The limeworkers’ excavations revealed some stratigraphic relationships but they have obscured others. Partly because of this, controversy surrounds the supposition about whether there are separated depositional basins within the overall site and, if so, whether strata can be securely correlated. This is important because a reconstruction of an overall stratigraphic sequence was used as a basis for a magnetostratigraphic reversal record and by which the site has been tentatively dated. There is qualification and disagreement about the origin of the various flowstones and the actual depositional environment of the muds and silts. Evidence is presented which rules out some previous interpretations. From the point of view of the Australopithecine fossils themselves, it can be said that the calcite matrix in which they were provenanced was a low-energy environment and that the dense bone accumulation of this layer almost certainly did not arise by the action of floods, as previously supposed. The most likely main cause of the dense accumulation was hyena denning activity. It is clear that further work is needed to see how a reliable overall sequence can be established and that closer sampling is required for magnetostratigraphy.
Tracing the record of early alluvial tin mining on Dartmoor, UK
Authors: Thorndycraft Varyl R. , Pirrie Duncan , Brown Anthony G. 
Published: April 2008

Abstract

Although there has been considerable speculation, there is as yet no conclusive evidence to confirm Dartmoor as a tin producing region in prehistory. This is in part due to extensive tin mining on the moor during the Medieval period destroying evidence of earlier mining activity. This paper presents the preliminary results of an integrated mineralogical and geochemical geoarchaeological approach to identifying the record of early mining activity. Floodplain sedimentary successions, that have not themselves been mined, and are downstream of known areas of tin streaming, retain a geochemical record of the mining activities because the early tin streaming released large quantities of mine waste tailings. Where these successions can be dated, they provide an indirect means of testing the record of mining activity on Dartmoor. Geochemical and mineralogical analyses of datable fluvial sediments aimed to (a) distinguish between natural and mine contaminated sediments, and (b) to date the onset of sediment aggradation caused by tin mining activity in the headwaters. Results from the Avon Valley show negligible Sn concentrations in basal silts that are dated to pre-2845 ± 45 yrs
bp
. Overlying silts are enriched in Sn and were deposited after 1560 ± 40
ad
, suggesting that the Sn enrichment corresponds with tin streaming in the 16th century. In the Erme Valley, significant Sn enrichment post-dates an organic-rich silt dated at 1280 ± 45
ad
. At both sites there is sediment aggradation coupled with an enhancement in Sn concentration consistent with mine waste contamination as a result of Medieval tin streaming.
Geochemistry and the early alum industry
Authors: Millard Andrew R. 
Published: April 2008

Abstract
One of the earliest chemical industries in Britain was the alum production industry. The early alum industry relied on a complex series of extractions from suitable shale deposits, until the rise of alternative methods in the 19th century, based on industrially produced sulphuric acid. Relatively little is known about the actual processes involved. This paper discusses the evidence that can be gleaned for the chemical processes involved and reports investigations on residues recovered from waste tips at the 17th–18th century alum works at Carlton Bank, North Yorkshire. For the first time it can be said that the sulphur content of the alum shale would have limited yields from the alum production process. Wide variability in the sulphur content of unworked shale implies variable yields in the alum production process, which may have contributed to the historically recorded boom and bust of individual alum works. Analyses of waste calcined shale were shown to be of limited value without experimental reconstruction of shale processing. Future investigations need to concentrate on waste residues recovered from alum works during excavations, and on reconstructions of the process.
Geophysical imaging of the shape of granitic intrusions at depth: a review
Authors: Améglio L. , Vigneresse J. L. 
Published: April 2008

Abstract
This review deals with direct evidence (field statements and geochemistry) and indirect observations (modelling experiments, analogical models, and geophysics) on granite plutons to model their shape at depth. 3D modelling of granite plutons can be achieved using geophysical tools. Amongst these tools, heat-flow and heat-generation data used earlier to estimate the thickness of granitic plutons appear inadequate. Electrical methods are strongly influenced by near-surface heterogeneities and temperature, which minimize their effectiveness at depth. Magnetic surveys provide information on contacts between pluton and country rocks, since magnetic halos are appropriate to delineate surface contours, but the technique lacks the resolution to reveal deep boundaries. Anisotropy of magnetic susceptibility is particularly well adapted to determine the internal structures of plutons. Seismic profiles at usual frequencies (30–80 Hz) define the layered structure of the floor of several bodies but fail to show the rock-type variations and their internal fabrics, because of their low impedance contrasts. Conversely, high-resolution seismic reflection profiles reveal fault structures in granites but the pluton’s floor remains transparent. Gravity measurements have been widely applied in granites and owing to the 3D inversion of data, the shape of the pluton at depth and depth of its floor may be derived with confidence from density contrasts.
Structure and geophysics of the Gåsborn granite, central Sweden: an example of fracture-fed asymmetric pluton emplacement
Authors: Cruden Alexander R. , Sjöström Håkan , Aaro Sven 
Published: April 2008

Abstract

The emplacement mechanisms of the Palaeoproterozoic Gåsborn granite, a satellite of the Transscandinavian Igneous Belt (TIB), are investigated using an integrated structural and geophysical approach. The pluton is discordant to
c
. 1.89 Ga folded supracrustal rocks that were deformed and metamorphosed at
c
. 1.85–1.80 Ga during the Svecokarelian Orogeny. Emplacement occurred at a depth of
c
. 10 km, within a regime of late Svecokarelian dextral transpression. Deformation of the pluton during cooling resulted in the formation of a variably developed foliation in the granite and deflection of less competent wall-rock units around its western and eastern contacts. Later E-W Sveconorwegian shortening resulted in the formation of shear zones that affect one of the pluton margins and may contribute to a component of the observed wall-rock distortion. The granite is situated above strong NNW-trending linear magnetic and negative gravity anomalies, which are interpreted to correspond to an important early Svecokarelian shear zone. The geophysical data indicate that the pluton is markedly asymmetric and modelling of the residual gravity field suggests that it consists of a deep root zone in the west and a thin sill-like body, which makes up most of the east and south parts of the body. Emplacement of the sill-like part occurred by lateral flow of magma from the root zone accommodated by downwarping of the underlying units. Intrusion of the thicker, discordant west part may have been accommodated by a combination of roof lifting and floor depression, aided by displacement on an active shear zone.
Petrology, magnetic fabric and emplacement in a strike-slip regime of a zoned peraluminous granite: the Campanario-La Haba pluton, Spain
Authors: Alonso Olazabal A. , Carracedo M. , Aranguren A. 
Published: April 2008

Abstract

This paper reports field, petrological and structural data of the peraluminous cordierite-andalusite-bearing Campanario-La Haba granite. Crystallization age is constrained by Rb-Sr whole-rock dating at 309 ± 6 Ma (with (
87
Sr/
86
Sr)
i
= 0.70739 ± 0.00038) and took place during late Hercynian tectonic events. The pluton shows a petrographic zonation, although there are no marked differences in chemical compositions between the margin and the centre of the intrusion. Petrography, mineralogical data and geochemical modelling indicate melt generation by partial melting of a metasedimentary protolith, probably with some mantelic contribution as shown by its low Sr
i
value, followed by emplacement at
P
< 3 kbar. The internal structure of the pluton resulted from the lateral spreading in the stretching direction given by an N120–130E dextral strike-slip zone and the external geometry seems to be strongly conditioned by faults (Riedel R type fractures) formed in the host rocks. This emplacement model agrees with that defined for the adjacent Extremadura granitic plutons and for the Los Pedroches batholith suggesting the existence of a dextral regional shear-zone in the South branch of the Central Iberian Zone.
Evidence of magmatic hybridization related with feeding zones: the synkinematic Guitiriz granitoid, NW Iberian Massif
Authors: Menéndez M. , Ortega L. A. 
Published: April 2008

Abstract

The hybridization zone of Guitiriz (NW Iberian Massif) displays numerous features resulted from the interaction of two contemporaneously emplaced felsic and intermediate magmas. A combined study, including field geology, petrography, chemistry and Sr isotopic data, reveals a simple two-component mixing between a mantle-derived magma with an initial
87
Sr/
86
Sr isotopic ratio <0.7042 and a crustal-derived component with an initial Sr isotopic ratio > 0.7104. Both magmas rose through a common feeding zone developed in an extensional regime in which favourable conditions for magma mixing occurred. Calculated emplacement temperature and pressure for the Guitiriz hybridization zone are 700 °C and 2.5 kbar, respectively, and are comparable with those estimated from regional metamorphism. Magmatic epidote occurrence, exhibiting textural and compositional characteristics suggestive of magmatic origin, does not require high-pressure granite solidification. Its presence may be related to a rapid magma transport through the feeding zone that favoured the preservation of epidote.
Analysis and interpretation of Holocene sedimentary sequences in the Humber Estuary
Authors: Ridgway J. , Andrews J. E. , Ellis S. , Horton B. P. , Innes J. B. , Knox R. W. O’B. , McArthur J. J. , Maher B. A. , Metcalfe S. E. , Mitlehner A. , Parkes A. , Rees J. G. , Samways G. M. , Shennan I. 
Published: April 2008

Abstract

The interpretation of the Holocene evolution of the Humber Estuary has been made possible only through integrated multidisciplinary studies involving
inter alia
: drilling, to obtain sedimentary records of the Holocene Estuary fill; multi-element, carbon-nitrogen-sulphur and stable carbon isotope geochemistry; heavy and clay mineralogy; palaeomagnetism; radio-carbon dating; and pollen, diatom and foraminiferal studies. Eight chemostratigraphic suites and 14 palaeo-environments have been recognized. Sediment types, environments of deposition and provenance change in response to rising sea-level, showing a range from freshwater fluvial deposition of locally derived terrestrial sediment to intertidal and subtidal deposition of sediments from marine sources. The methods used are illustrated with reference to sediment cores from inner and outer estuary locations. The results show that Holocene environmental characterization is most secure when a number of different, but complementary, techniques are used. The integration of radiocarbon dates with palaeomagnetic and geochemical data improves the understanding of the presence and significance of time breaks, which is crucial to constraining sedimentation rates and material budgets.
Implications of a microfossil-based transfer function in Holocene sea-level studies
Authors: Horton B. P. , Edwards R. J. , Lloyd J. M. 
Published: April 2008

Abstract
Fifty-two sea-level index points are described from samples collected within the Land-Ocean Interaction Study area. The vertical relationship between relative sea-level and a reference water level for each index point was estimated using two contrasting methods: a lithological-based approach, which is routinely employed in sea-level studies, and a foraminiferal-based transfer function. Comparison of the two methods reveals that the range of the former is 0.14 ± 0.09 m smaller than the latter because the foraminiferal-based transfer function takes into account differences in tidal ranges between study sites. Furthermore, the reference water-level estimates of transgressive index points using the foraminiferal-based transfer function are on average 0.19 ± 0.12 m higher than those of the lithological-based approach. This may be due to the rapid response time of foraminiferal assemblages relative to lithological indicators or the uneven spatial sampling within the contemporary foraminiferal data set. Whilst these inter-method differences are small in magnitude, they are comparable in size to the scale of changes under investigation by recent high-resolution sea-level studies. In contrast, the reference water levels of both methods are comparable for regressive and basis index points. Index points from clastic sediments were also produced using the foraminiferal-based transfer function. Calcareous foraminifera from intertidal environments can be used to produce indicative meanings and supply material for accelerator mass spectrometry radiocarbon dating. This method expands the range of stratigraphic sequences that can be employed in sea-level reconstruction by redressing the over-reliance on transgressive and regressive contacts.
Luminescence dating of fine-grain Holocene sediments from a coastal setting
Authors: Bailiff I. K. , Tooley M. J. 
Published: April 2008

AbstractA detailed study of a core of Holocene age from a site (Adventurers’ Land, F21) in the Fenlands, UK, based on the measurement of infra-red-stimulated luminescence (IRSL) with silt-sized fractions of water-laid deposits has yielded a sequence of 24 luminescence ages. An additive dose procedure was applied to evaluate the palaeodose, and the annual dose was assessed on the basis of radioactivity and elemental analyses of samples taken from the core. The proportions by weight of the mineral fraction of water and organic material within the sediments ranged fromc.20 to 170% for the former and betweenc.10 and 25% for the latter. Overall, the sequence of IRSL age evaluations is consistent with the calibrated radiocarbon ages obtained for three intercalated organic horizons within the core. Although the luminescence ages for F21A do not possess a resolution that would enable rates of sedimentation between the organic sediments to be determined with confidence, the general trend of the luminescence ages with depth suggests a chronological resolution of the order of 1 ka or better.
The development of a methodology for luminescence dating of Holocene sediments at the land-ocean interface
Authors: Clarke M. L. , Rendell H. M. 
Published: April 2008

Abstract

The main challenge in luminescence dating is to provide accurate ages for sediments derived from hillslope, fluvial and marine environments where grains have been transported and deposited by water. A new methodology has been devised for dating Holocene age sediments from the land-ocean interface. Alkali feldspars are recommended as the ideal dosimeter in these environments as they are: rapidly zeroed, have high sensitivity to dose, have an internal dose rate from the decay of
40
K, have signal intensities that are much higher than for quartz, and the equivalent doses (EDs) determined are not affected by chemical weathering. Studies of the fundamental characteristics of feldspars have been used to optimize the luminescence signal for use in dating applications. A quality assurance technique for discriminating between those samples that will give accurate dates and those that will yield inaccurate dates has been developed and is tested here on coastal-zone sediments from Lincolnshire. Sampling from sediment exposures rather than cores minimizes the uncertainties related to past water content fluctuations.
The Holocene evolution of the Humber Estuary: reconstructing change in a dynamic environment
Authors: Metcalfe S. E. , Ellis S. , Horton B. P. , Innes J. B. , McArthur J. , Mitlehner A. , Parkes A. , Pethick J. S. , Rees J. , Ridgway J. , Rutherford M. M. , Shennan I. , Tooley M. J. 
Published: April 2008

Abstract

The Holocene sequence of the Humber Estuary displays a wide range of sediment types within which the preservation of microfossils is highly variable. Its evolution has been reconstructed using a range of environmental proxies with chronological control provided by more than 90 radiocarbon dates. Results are presented of diatom analyses from three cores typical of the inner, middle and outer estuary (HMB20, HMB7 and HMB12) and of three cores that illustrate the role of organic deposits (peats) and their associated pollen (HMB13, HMB12 and the Ancholme Valley) in the definition of sea-level index points. The reconstruction of relative sea-level change shows a rapid rise in the early Holocene, followed by a reduced rate of rise in the mid-late Holocene. This reconstruction, together with information on the pre-Holocene surface and the different palaeoenvironments from the cores have been integrated within a geographical information system and then interpreted to yield a series of palaeogeographical maps of the Humber at 1000-year time slices between 8 and 3 cal. ka
bp
. The marine transgression progressed up the estuary after 8 cal. ka
bp
, reaching the inner estuary by 6 cal. ka
bp
. The expansion of intertidal environments probably reached its maximum around 3 cal. ka
bp
. Changes since 3 cal. ka
bp
are described using archaeological and historical records. Tidal asymmetry is a major controlling factor on the balance of sediment accretion and erosion in the estuary. Sedimentary and bathymetric evidence suggests a damped oscillation between flood and ebb asymmetry in the Humber over the Holocene period. Such a conclusion would be of great importance to estuarine managers and users since it could be used to predict the future development of the estuary.