bluuebunny/crossref_metadata_2025_split huggingface dataset:
Late Quaternary glacial history and short-term ice-rafted debris fluctuations along the East Greenland continental margin
Authors: Stein Ruediger , Nam Seung-il , Grobe Hannes , Hubberten Hans 
Published: September 2007

Abstract

High-resolution stable oxygen and carbon isotope and sedimentological investigations were carried out on four west-east profiles at the East Greenland continental margin between 68° and 75°N. The sediment cores represent distinct glacial/interglacial palaeoclimatic episodes over the past 190 ka. Based on oxygen isotope stratigraphy and AMS
14
C dating, our data can be well correlated with the global climate record. However, there are some excursions from the global climate curve suggesting a local/regional overprint by meltwater events of the Greenland Ice Sheet, especially at the beginning of isotope stage 3 and during Termination 1. Distinct high-amplitude variations in supply of ice-rafted debris (IRD) indicate repeated advances and retreats of the Greenland Ice Sheet, causing fluctuations in the massive production and transport of icebergs into the Greenland Sea. During the last 190 ka, a number of IRD peaks appear to be correlated with cooling cycles observed in the GRIP Greenland Ice Core. Drastic events in iceberg discharge along the East Greenland continental margin recurred at very short intervals of 1000–3000 years (i.e. much more frequently than the about 10 000 years associated with Heinrich events), suggesting short-term collapses of the Greenland Ice Sheet on these time-scales. These late Weichselian Greenland Ice Sheet oscillations appear to be in phase with those in the Barents Sea area. Maximum flux rates of terrigenous (ice-rafted) material were recorded at the continental slope between about 21 and 16 ka, which may correspond to the maximum (stage 2) extension of glaciers on Greenland. The beginning of Termination I is documented by a distinct shift in the oxygen isotopes and a most prominent decrease in flux of IRD at the continental slope caused by the retreat of continental ice masses.
Late Quaternary sedimentation along a fjord to shelf (trough) transect, East Greenland (
c.
68° N)
Authors: Andrews J. T. , Jennings Anne E. , Cooper T. , Williams Kerstin M. , Mienert J. 
Published: September 2007

Abstract

The East Greenland continental margin between
c.
66 and 68° N consists of a major fjord/trough system that extends from Kangerdlugssuaq Fjord, along Kangerdlugssuaq Trough to Denmark Strait. Measurements of the temperature and salinity of the water column along this transect indicates that ‘warm’ water (0–2°C) underlies the surface Polar Water of the East Greenland Current. A series of short (1–3 m) gravity cores along the fjord/trough transect have sufficient numbers of foraminifera that a suite of AMS
14
C dates has been obtained, including both basal and core-top age estimates. Rates of sediment accumulation vary through space and time; over the last 1 ka estimates vary from
c.
3 to 0.1 m. These dates and measurements of sediment density, together with measurements of the percentages by weight of total organic carbon and biogenic silica, are used to show graphs of fluxes of the organic and inorganic sediment components over the last 1–14 ka. An analysis of the net flux of foraminifera indicates a reduction in numbers during the Younger Dryas chronozone and a general similarity with data from the Renland (East Greenland) ice core data.
Sedimentological examination of the Late Weichselian sea-level history following deglaciation of northern Denmark
Authors: Richardt Niels 
Published: September 2007

Abstract

Modern sedimentological principles are used to examine the Late Weichselian marine history of Vendsyssel, northern Denmark. The purpose is to determine significant sea-level events and to outline a new relative sea-level curve. Five significant events are found: deglaciation, high relative sea level (
c.
60 m above the present sea level), a rapid fall in relative sea level, a marked break in sea-level fall (
c.
20 m above the present sea level) and a renewed fall in relative sea level. The new sedimentologically based sea-level curve is compared with a classical and a revised ecologically based relative sea-level curve. These curves show an initial transgression following deglaciation. The new sedimentologically based curve shows no transgression. It is concluded that this curve is the most reliable. When comparing the new sea-level curve with regional data from Vendsyssel significant differences are found. A time transgressive deglaciation pattern and neotectonic movements might explain these differences. The isostatic position of the study area during the examined time span is sketched. Rapid isostatic uplift commenced as late as
c.
13 300 years
BP
, at least 1300 years after deglaciation of the area.
Deglaciation history and palaeoceanography of the western Spitsbergen margin since the last glacial maximum
Authors: Lloyd J. , Kroon D. , Laban C. , Boulton G. 
Published: September 2007

Abstract

Two high resolution cores from the Spitsbergen margin were studied to increase the understanding of the palaeoceanography and deglaciation of the Spitsbergen continental margin. Planktonic and benthic foraminiferal δ
18
O records along with foraminiferal abundance counts and dropstone analysis were used to interpret the palaeoceanography of the Spitsbergen margin and to link the marine record with deglaciation of the Barents Sea Ice Sheet. High foraminiferal and dropstone abundances during the Late Weichselian glacial maximum show that this period was characterized by seasonally ice-free conditions. The initial deglaciation recognized along the Spitsbergen margin is dated at 14.1 ka
BP
and represents the break up of the Barents Sea Ice Sheet, though some input from the Spitsbergen ice dome is likely. This initial deglaciation was produced by glacio-isostatic relative sea-level rise and/or by increased solar insolation after the minimum of the Late Weichselian. The first unequivocal deglaciation of Spitsbergen ice occurred at 13 ka, whereas the oceanographic regime was still dominated by polar waters. The beginning of the Holocene was heralded by a second deglaciation phase of the Spitsbergen ice mass. The first influx of North Atlantic waters causing rapid iceberg calving and melting was recorded at this time. Dropstone input virtually ended at approximately 9 ka
BP
when most glaciers had retreated beyond their present day positions. A short relatively cool episode produced by the retreat of the North Atlantic waters during the early Holocene was recorded along the Spitsbergen margin.
Late glacial air temperature, oceanographic and ice sheet interactions in the southern Barents Sea region
Authors: Vorren Tore O. , Laberg Jan S. 
Published: September 2007

Abstract

Stratigraphic records from three areas (the Andøya area, the continental slope and the continental shelf of the southern Barents Sea) are used to evaluate the history of the late glacial Barents Sea Ice Sheet and the northern Fennoscandian Ice Sheet. Two late glacial maxima are indicated: one before 22 ka
BP
(LGM I) and the younger after 19 ka
BP
(LGM II). A major deglaciation phase was initiated during a warm spell between 16 and 15 ka
BP
. During a drawdown of marine based ice sheets about 14.5 ka
BP
large parts of the southern Barents Sea Ice Sheet decayed. This deglaciation was retarded between 13.7 and 13 ka
BP
. Most of the eastern and northern Barents Sea was deglaciated during the Bølling-Allerød interstadial complex. During the LGM II there was an ice stream in the Bear Island Trough with an estimated velocity at the front of about 2.5 km/year. An average accumulation rate of 0.3–0.4 m/year is estimated for the drainage area of the Bear Island Trough Ice Stream. A close interrelation exists between summer air temperatures and the waxing and waning phases of the northern Fennoscandian and southern Barents Sea ice sheets. It is suggested that most of the ice sheet decay was due to climatic warming, which caused thinning of the ice sheets, making them susceptible to decoupling from the sea bed and increased calving. The subsequent halts/readvances were due to climatic deteriorations caused by huge inputs of icebergs to the Norwegian Sea which cooled the surface water and in turn promoted sea ice preservation through the summer season and thereby increased the albedo.
Late Weichselian deglaciation of the Barents Sea and low salinity events in the Norwegian Sea
Authors: Punkari Mikko 
Published: September 2007

Abstract
The glacial geomorphology of the northwestern Russian Plain, Pechora lowland, northern Urals and southern Novaya Zemlya was mapped using Landsat satellite imagery. The deglaciation of the ice sheets around the Barents Sea was outlined using geological mapping, published land uplift data and previous observations. The amount of glacial meltwater produced during the deglaciation is compared with other freshwater sources. Freshwater discharges from proglacial lakes are approximated using this ice sheet reconstruction. Variations in precipitation are estimated using ice accumulation rates from an ice core in Greenland.

The ice sheets spreading from the continent and islands surrounding the Barents Sea melted quickly 14-9 ka
BP
. According to glacial flow patterns and the compilation of
14
C dates, the separation of the Scandinavian and Novaya Zemlya ice sheets occurred in the marine zone between the Kanin and Kola Peninsulas at about 13 ka
BP
. The Dvina-Pechora proglacial lake, which had accumulated south of the confluence zone, drained into the Barents Sea, west of the Kanin Peninsula. The size of the lake was about 350 000 km
2
and the volume of water of the order of 10 000 km
3
, equivalent to a 3 cm global sea-level rise.

Low salinity periods at 15-13 ka
BP
have been reported in the North Atlantic and Norwegian Sea. These have been associated either with active glacier calving and melting or with changes in the oceanic circulation system. The rapid decay of the ice sheets at 14-11 ka
BP
yielded meltwater about 600 km
3
/year, but the greatly increased precipitation during the Bölling interstadial at 12.3 ka
BP
became the most important source of freshwater entering the sea. The proposed freshwater pulse from the proglacial lake was a short-lasting event, but it may possibly be recorded in the marine stratigraphy by the oxygen isotope signal preserved in calcite from planktonic foraminifera.
Detailed survey of the western end of the Hurd Deep (English Channel): new facts for a tectonic origin
Authors: Lericolais G. , Guennoc P. , Auffret J.-P. , Bourillet J.-F. , Berne S. 
Published: September 2007

Abstract
During the ‘Sédimanche 2’ survey, a study of the western end of the Hurd Deep was carried out using new high-resolution geophysical techniques. The obtained results, i.e. bathymetry, acoustical imaging and seismic profiling, determine a tectonic control on the first excavation of Hurd Deep, a complex infilling and present-day sediment dynamics.
In size and geometry, the Hurd Deep is a unique feature in the English Channel, terminating abruptly at its western end. It is incised into Jurassic and Late Cretaceous sediments. Except for the trough itself, the sea floor is extensively levelled at a depth between 70 and 90 m.
The Hurd Deep infill, revealed by high-resolution seismic data, is characterized by a set of five main sequences. The thickness of the infill averages 80 m along the axis of the trough and reaches a maximum of 140 m. The side-scan sonar mosaic shows active sediment dynamics characterized by the presence of dunes on the southern part of the present trough.
A Neogene tectonic origin for the Hurd Deep and the interplay of erosion and sedimentation during the last glacial and interglacial periods are presented in terms of geomorphology and sequence stratigraphy.
Evolution of a nearshore and coastal macrotidal sand transport system, Queen Charlotte Islands, Canada
Authors: Barrie J. V. , Conway K. W. 
Published: September 2007

Abstract
An extensive (40 km) coastal plain is prograding on the north coast of the Queen Charlotte Islands off the Pacific margin of Canada while the entire 120 km eastern coast of Graham Island is actively eroding. At the junction of these two systems is Rose Spit, which extends northeastward at a point of sediment transport convergence. Historical bathymetrical data and aerial photographs indicate that a spit platform extends 10 km to the northeast and at least four portions (up to 4 km in length) of the platform bank have become emergent since 1911. The area is seismically active and subject to storm-related sediment transport events superimposed on strong semi-diurnal tidal flows. The rapid emergence of the offshore banks and the net coastal changes are primarily controlled by: (1) convergence of sediment transport between the waters of Hecate Strait to the south and Dixon Entrance to the north, particularly during winter storms; and (2) localized tectonic uplift.
Sediment is transported north from the shallow waters of Hecate Strait by southeasterly winter storms and east, by longshore transport, along the accreting northern coast of the Queen Charlotte Islands to converge at Rose Spit. A ‘hydraulic fence’ has formed resulting in the creation of the elongate spit platform with emergent sand bars, east of the spit. Transpressional folding has occurred in this area east of the Queen Charlotte Fault, which separates the North American and Pacific Plates. This has resulted in localized uplift since Pliocene time, complementing the accretion process.
Geophysics in offshore site investigation: a review of the state of the art
Authors: Davis A. M. 
Published: September 2007

Abstract
Geophysical techniques for seabed and sub-seabed site investigation can be divided into two categories: those providing information on gross structural (geological) and stratigraphical relations, and those producing quantitative data which can be used to predict sediment behaviour under applied loading. The past few years have seen key developments in both fields which have come about through fundamental improvements in data acquisition (technological and procedural), and through an improved understanding of geophysical-geotechnical property relations. For example, high-resolution seismic reflection signatures are now routinely recorded in digital format, and, given the appropriate data quality and processing software, it is now possible to extract geotechnically significant information from the reflection response. Seismic refraction techniques are also beginning to be more widely used to provide quantitative information on the engineering properties of seafloor materials; the seismic shear wave velocity is of particular interest, since it is now being recognized as an indicator of sediment strength and stiffness.
From a review of available data and the results of validation exercises, it would seem that offshore engineering and environmental surveys could reap considerable benefit from these and a range of other related geophysical developments.
Insight into the enigma of Neoproterozoic manganese and iron formations from the perspective of supercontinental break-up and glaciation
Authors: Bühn Bernhard , Stanistreet Ian G. 
Published: September 2007

Abstract

The genesis of manganese and iron formations (MnF and IF) is a closely related process during the Proterozoic, in which oceanic crustal venting provided metal-rich solutions to be deposited on adjacent continental shelves. Their deposition in condensed marine sequences occurred when continental break-up initiated a major transgression and provided favourable conditions for precipitation of chemical sediments from seawater. The Neoproterozoic Rodinian supercontinental break-up shows the relationship between this tectonic process, climate, and MnF/IF genesis. Metallogenesis followed particular rift-drift transitions during supercontinental break-up. MnFs/IFs are often associated with glaciomarine sedimentary rocks. Higher O
2
/CO
2
during continental rifting would, through inducing glacial conditions and withdrawing seawater, increase ocean salinity and thereby allow both deposition of glaciomarine sediments and precipitation of evaporites. Salinities would have been particularly enhanced in the restricted oceanic basins provided by early supercontinental rifting, where atmospheric evaporation would also have played a part. Accumulation of Mn and Fe in the Neoproterozoic may be directly related to a probably glacially derived increased ocean salinity that promoted accumulation and storage of Mn and Fe in ocean water through increased Mn, Fe, and Ba(?) solubility. Very similar processes may have been effective in Palaeoproterozoic times, although then a higher amount of Fe and Mn discharge and different ocean chemistry would have superseded the effect of ocean salinity. Chemical Mn and Fe precipitates related to supercontinental break-up in the Proterozoic as well as the Phanerozoic indicate a similar relationship between tectonics and ore accumulation. The resultant close time and space relationship between potent oceanic source and suitable continental-shelf depositional settings optimised accumulation and preservation of ancient Mn-Fe deposits. This scenario is at variance from present-day environments where source and suitable precipitation areas of long-term preservation potential are mostly widely separated in space.
An EPMA and SEM study of the Mn-oxide mineralization of Kato Nevrokopi, Macedonia, northern Greece: Controls on formation of the Mn
4+
oxides
Authors: Michailidis K. M. , Nicholson K. , Nimfopoulos M. K. , Pattrick R. A. D. 
Published: September 2007

Abstract

EPMA and SEM studies of tunnel-structured todorokite and nsutite and layer-structured chalcophanite and birnessite from the Kato Nevrokopi battery grade Mn-mineralization were performed. The chemistry of todorokite, formed at hypogene and supergene environments in an increasing order of weathering, reflects different pH and oxidation conditions. The data also point to a clear dependence of the development of late stage hypogene and early supergene Mn
4+
-oxide paragenesis on the host rock and protore composition and the mobilities of base metals (mainly Zn), alkalis and alkaline earths (mainly Ca).

The chemistry and development of (large cation-bearing) nsutite as
in situ
oxidations and banded poorly crystalline (with structural defects) aggregates in veins and associated karstic cavities, together with birnessite, indicates the influence of climate, oxidation and water table fluctuations. The data on chalcophanite revealed a deposition, under low
f

O
2

conditions, from acid meteoric fluids produced by weathering of vein sulphides. Birnessite formation reflects a prevalence of higher
f

O
2

in weathered veins and karstic cavities.

The evolution of well developed layer structures through poorly crystalline to amorphous tunnel-structured nsutite is probably controlled by a Zn-saturation of the ore fluids.
Recent manganese oxide deposits in Hokkaido, Japan
Authors: Miura Hiroyuki , Hariya Yu 
Published: September 2007

Abstract

Recent manganese oxide deposits and manganese-bearing hot-spring waters from Hokkaido, Japan have been studied. There are many active hot-springs in the volcanic zones in Japan and stable isotope data (
δ
D) show that the hot-spring water is derived from surface water. Some hot-spring waters precipitate manganese oxides. They are black, soft and muddy. SEM micrographs show a pipe structure coated by manganese oxides which indicates the role of microorganisms in manganese precipitation. X-ray powder diffraction reveals that they consist of todorokite or birnessite. Pyrolusite is not a primary product from hot-spring waters, but a recrystallized product in the post-depositional environment. Manganese oxides alternated with calcareous sinter and are crusty and consist of rancieite. The concentration of heavy metal elements in manganese oxide is controlled by the crystal structure of magnanese oxide minerals present in the deposits and todorokite contains the most heavy metal elements. REE concentration varies widely and the negative Ce anomaly is an indicator of depositional rate.
Geochemistry of manganese oxides: metal adsorption in freshwater and marine environments
Authors: Nicholson Keith , Eley Mark 
Published: September 2007

Abstract

The effect of pH and metal ion concentration on the adsorption of Cu, Co, Cd, Mn, Ni and Zn onto manganese oxides was investigated. The oxides used in the experiments were deposited around individual sand grains in water treatment filter beds in NE Scotland and show reproducible adsorption profiles regardless of location or age. The oxides remained amorphous throughout the four-year study period, and show an inferred pH
ZPC
of 1.5. Metal adsorption increases towards more alkaline pH. The adsorption series Co > Cu > Cd > Zn > Mn > Ni is shown at pH 3 and Cu > Co > Cd > Mn > Zn > Ni at pH 6. Changing the concentration of the metal ions in solution leads to an increase in the mass of metal adsorbed, though the relationship is not linear as the proportion of metal taken up falls as concentration rises. Adsorption from an artificial seawater solution shows a significant reduction in the amount of metal taken up in all cases except Cu which shows an adsorption profile comparable with that in deionized water. The linear Freundlich isotherm accurately and reproducibly models the adsorption profile of all metals at each pH and concentration examined. The data do not, however, replicate the enrichment sequence observed in manganese nodules. The study demonstrates that for the enrichments observed in manganese nodules to be attained, the active oxide surface must be replenished by regular precipitation of fresh oxide material to enable continued adsorption to take place.
The determination of the valency of manganese in mineralogical and environmental samples by X-ray emission spectroscopy
Authors: Gamblin S. D. , Urch D. S. 
Published: September 2007

Abstract

The K
β
X-ray emission spectrum arising from 3
p
→ 1
s
transitions in transition metal ions can be complicated by interaction between unpaired 3
d
electrons and the odd 3
p
electron in the final state. A non-diagram line, K
β′
appears at lower emission energy than the diagram line K
β
1,3
. For lighter transition metals the intensity ratio of K
β′
to K
β
1,3
decreases with the number of unpaired 3
d
electrons. This enables this intensity ratio to be used to determine oxidation state.

This effect is demonstrated for the simple oxides MnO, Mn
2
O
3
and MnO
2
, and for the anion MnO
4
−. Distinct spectra are obtained that can be related to the oxidation state of the manganese. The valency of manganese is then determined in mineral samples and in sand grains coated with manganese encrustations from water purification plants.
One-man-operable probe permeameters
Authors: Prosser D. J. , Hurst A. , Wilson M. R. 
Published: September 2007

Abstract
A steady-state probe permeameter is designed that is robust, insensitive to moisture and can be operated using a low-pressure gas source. Consequently, substantial reduction in weight and bulk are possible and a truly one-man-operable, lightweight (<5 kg) instrument is constructed. Tests on natural samples using a prototype instrument reveal a similar level of precision to other permeameters over a wide range of permeability.