scholarly journals The Geochemistry and Bioturbation of Clay Sediments Associated with Amalgamated Crusts at the Gagua Ridge

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 177
Author(s):  
Shuai Chen ◽  
Zhigang Zeng ◽  
Xiaoyuan Wang ◽  
Xuebo Yin ◽  
Bowen Zhu ◽  
...  
Keyword(s):  
Sediment Surface ◽  
Abrupt Increase ◽  
Crust Formation ◽  
Material Sources ◽  
Deep Waters ◽  
Volcanic Glasses ◽  
Clay Sediment ◽  
Basic Volcanic ◽  
Mineralogical Compositions ◽  
Oxic Sediment

Based on the analysis of geochemical and mineralogical compositions, deep sea clay sediment characteristics and their material sources were examined in the eastern flank of the Gagua Ridge. The mineralogy mainly consists of detrital clay minerals, quartz, and authigenic phillipsite. There is scarce biogenic debris (siliceous or calcareous). The consolidated sediments are more enriched in Si, Al, K, Na, Li, Sc, Cr, Rb, and Cs than the associated crusts and nodules. The unmixed sediment samples were mainlycontributed by Asian eolian dust. The onset of the outer Fe-Mn crust growth nearly coincides with the Central Asia aridification event at ~3.5 Ma, which resulted in an abrupt increase in eolian flux of Asian dust. Intensified surface primary productivity is assumed to bring more metals to deep waters, and eventually facilitate the outer Fe-Mn crust formation. Authigenic phillipsite may come from the alteration of local basic volcanic glasses and cause excess Al, high Al/Ti, and low Si/Al ratios. However, phillipsites hardly affect the abundance of rare earth elements (REEs) and their patterns. In addition, the investigation of two kinds of burrows inside the consolidated sediments reveals that the inner nodules of the amalgamated crusts may remain on the oxic sediment surface, due to frequent benthic activities.

scholarly journals Oxycline oscillations induced by internal waves in deep Lake Iseo

2018 ◽  
Author(s):  
Giulia Valerio ◽  
Marco Pilotti ◽  
Maximilian Peter Lau ◽  
Michael Hupfer
Keyword(s):  
Internal Waves ◽  
Water Layer ◽  
Sediment Surface ◽  
Chemical Gradient ◽  
Deep Lakes ◽  
Deep Lake ◽  
Deep Waters ◽  
Basin Scale ◽  
First Time

Abstract. Lake Iseo is undergoing a dramatic de-oxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the prealpine area that are, to a different extent, suffering from reduced deep water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments is a major concern. Since the hydrodynamics of this lake was shown to be dominated by internal waves, in this study we investigate for the first time the role of these oscillatory motions on the vertical fluctuations of the oxycline, currently situated at a depth of around 95 m, where a permanent chemocline inhibits deep mixing by convection. Temperature and dissolved oxygen data measured at moored stations show large and periodic oscillations of the oxycline, with amplitude up to 20 m and periods ranging from 1 to 4 days. A deep dynamics characterized by larger amplitudes at lower frequencies is shown to be favoured by the excitation of second vertical modes in strongly thermally stratified periods and of first vertical modes in weakly thermally stratified periods, when the deep chemical gradient can support baroclinicity anyhow. These basin-scale internal waves cause in the water layer between 85 and 105 m depth a fluctuation of the oxygen concentration between 0 and 3 mg L−1 that, due to the bathymetry of the lake, changes the redox condition at the sediment surface. This forcing, involving about 3 % of the lake's sediment area, can have major implications for the biogeochemical processes at the sediment water interface and for the internal matter cycle.

Carbonate spherules and botryoids as lake floor cements in the East Kirkton Limestone of West Lothian, Scotland

1993 ◽  
Vol 84 (3-4) ◽  
pp. 213-221 ◽  
Author(s):  
Gordon M. Walkden ◽  
J. Roddy Irwin ◽  
Anthony E. Fallick
Keyword(s):  
Stable Isotope ◽  
Fresh Water ◽  
Hot Spring ◽  
Organic Substrate ◽  
Sediment Surface ◽  
Seasonal Effect ◽  
Volcanic Terrain ◽  
Lake Floor ◽  
Basic Volcanic ◽  
Lake Waters

ABSTRACTThe East Kirkton Limestone is typically a carbonate/organic laminite characterised at many levels by abundant radial-fibrous calcite (RFC) spherules and by less common larger stromatolite-like accretions of laminated botryoidal RFC. The spherules are mostly c. 1 mm in diameter and have cyanophyte and chlorophyte inclusions. Some spherules enclose parallel bundles of complete cyanophyte fibres and probably grew within a living cyanophyte mat. The botryoidal accretions were commonly seeded upon wood and other exposed organic remains such as bone, and they completely enclose twigs and branches where these were held above the sediment surface. Botryoidal accretions commonly contain the remains of a benthos of cyanophytes, chlorophytes and ostracods.Both types of calcite have carbon and oxygen stable isotope values similar to those of known fresh-water precipitates. Their stable isotope and trace element geochemistries are consistent with precipitation on the floor of a tropical fresh-water lake within a volcanic setting, but removed from the influence of any hot-spring activity. Spherules and botroids are mineralogically closely similar and, whilst precipitation may have been biogenically mediated, they are regarded as passive lake floor cements.The carbonate laminae are dominated by rhombohedral calcite. Many of these laminae may have originated as calcite suspensoids which settled to the lake floor during relatively brief precipitation events, blanketing the normally richly organic substrate, smothering the cyanophyte mats, and leading to the preservation of individual organic laminae. Crystals later became enlarged and intergrown within the sediment, but this occurred early and prior to significant compaction, because detail of fragile and degradable organic constituents is commonly preserved. The likely source of the carbonate is through leaching of the local basic volcanic terrain. The precipitation of two types of calcite implies regular fluctuations in the chemistry of the lake waters, or in the factors controlling precipitation, which may have been a biogenic and/or seasonal effect.

scholarly journals Oxycline oscillations induced by internal waves in deep Lake Iseo

2019 ◽  
Vol 23 (3) ◽  
pp. 1763-1777 ◽  
Author(s):  
Giulia Valerio ◽  
Marco Pilotti ◽  
Maximilian Peter Lau ◽  
Michael Hupfer
Keyword(s):  
Internal Waves ◽  
Water Layer ◽  
Sediment Surface ◽  
Chemical Gradient ◽  
Deep Lakes ◽  
Deep Lake ◽  
Deep Waters ◽  
Basin Scale ◽  
First Time

Abstract. Lake Iseo is undergoing a dramatic deoxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the pre-alpine area that are, to a different extent, undergoing reduced deep-water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments are a major concern. Because the hydrodynamics of this lake was shown to be dominated by internal waves, in this study we investigated, for the first time, the role of these oscillatory motions on the vertical fluctuations of the oxycline, currently situated at a depth of approximately 95 m, where a permanent chemocline inhibits deep mixing via convection. Temperature and dissolved oxygen data measured at moored stations show large and periodic oscillations of the oxycline, with an amplitude of up to 20 m and periods ranging from 1 to 4 days. Deep motions characterized by larger amplitudes at lower frequencies are favored by the excitation of second vertical modes in strongly thermally stratified periods and of first vertical modes in weakly thermally stratified periods, when the deep chemical gradient can support baroclinicity regardless. These basin-scale internal waves cause a fluctuation in the oxygen concentration between 0 and 3 mg L−1 in the water layer between 85 and 105 m in depth, changing the redox condition at the sediment surface. This forcing, involving approximately 3 % of the lake's sediment area, can have major implications for the biogeochemical processes at the sediment–water interface and for the internal matter cycle.

Deep Waters

2012 ◽  
Author(s):  
Yaddyra Peralta
Keyword(s):  
Deep Waters

“The Samoans Are Here!”: Samoan Ethnic Shows, 1895–1911

2020 ◽  
Vol 47 (2-3) ◽  
pp. 233-260
Author(s):  
Hilke Thode-Arora
Keyword(s):  
New Zealand ◽  
High Ranking ◽  
Material Sources

Abstract Between 1895 and 1911, three groups of Samoans traveled to Germany to take part in ethnic shows. There were titled and high-ranking persons in each of the groups. This article explores the recruiting, organizing, and reception of the shows, contextualizing the European and Samoan perspectives, which differed significantly. In addition to written, visual, and material sources in Samoan, New Zealand, and European archives and museums, the research is based on interviews with descendants of the Samoan travelers who could still be traced.

Influx of streaming methane into anoxic waters of the Black Sea basin

2019 ◽  
Vol 59 (6) ◽  
pp. 952-963
Author(s):  
Yu. G. Artemov ◽  
V. N. Egorov ◽  
S. B. Gulin
Keyword(s):  
Spatial Distribution ◽  
Black Sea ◽  
The Black Sea ◽  
Gas Bubble ◽  
Dissolved Methane ◽  
Anoxic Waters ◽  
Deep Waters ◽  
Methane Budget

Based on data on the spatial distribution and fluxes of streaming (bubbling) methane within the Black Sea, the rate of dissolved methane inflow to Black Sea deep waters was assessed. Calculations showed that gas bubble streams annually replenish the methane budget in the Black Sea by 1.2 109 m3, or 0.9 Tg, which is considerably less than determined by known biogeochemical estimates of components of methane balance in the Black Sea.

Calculation of the Glaze Recipe for Porcelain Feldspar Products Based on their Molecular Formula Rationalization

2008 ◽  
Vol 59 (2) ◽  
pp. 129-134
Author(s):  
Ion Teoreanu ◽  
Roxana Lucia Dumitrache ◽  
Stefania Stoleriu
Keyword(s):  
Raw Materials ◽  
Computer Programs ◽  
Point Of View ◽  
Raw Material ◽  
Easy Access ◽  
Molecular Formula ◽  
Design Equation ◽  
Material Sources

Any change of the raw material sources for glazes, economically, ecologically motivated, and also from the glaze quality point of view, is conditioned by the molecular formula rationalization and by the variation limits of the molecular formula, respectively. The proper glaze compositions are placed within their limit variation intervals with optimized processing and utilization properties. For this purpose, the rationalization criteria and procedures of molecular formulas are summarized in the present paper, as well as the results referring to their rationalization obtained in the authors� previous work. Thus, one starts from a base of raw materials that are selected, usable and also accessible for the design and producing of the glazes. On these bases the groundwork and the design equation for the glaze recipes are developed, exemplified for a single glaze. For an easy access to results, computer programs are used for an easy access to results.

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