Rock-magnetic proxies of wind intensity and dust since 51,200 cal BP from lacustrine sediments of Laguna Potrok Aike, southeastern Patagonia

2015 ◽  
Vol 411 ◽  
pp. 72-86 ◽  
Author(s):  
Agathe Lisé-Pronovost ◽  
Guillaume St-Onge ◽  
Claudia Gogorza ◽  
Torsten Haberzettl ◽  
Guillaume Jouve ◽  
...  
Keyword(s):  
Lacustrine Sediments ◽  
Magnetic Proxies ◽  
Wind Intensity

HOLOCENE AEOLIAN SEDIMENTATION AND EPISODIC MASS-WASTING EVENTS RECORDED IN LACUSTRINE SEDIMENTS ON LANGøYA IN VESTERåLEN, NORTHERN NORWAY

2016 ◽  
Author(s):  
Pål Ringkjøb Nielsen ◽  
◽  
Svein Olaf Dahl ◽  
Henrik Løseth Jansen ◽  
Eivind W.N. Støren
Keyword(s):  
Lacustrine Sediments ◽  
Mass Wasting ◽  
Northern Norway

COMPETITIVE REDUCTION OF FERRIHYDRITE AND NONTRONITE AND IMPLICATIONS FOR LACUSTRINE SEDIMENTS

2019 ◽  
Author(s):  
David M. Davis ◽  
◽  
Joshua Malidzo Chidzugwe ◽  
Daniel M. Deocampo
Keyword(s):  
Lacustrine Sediments ◽  
Competitive Reduction

scholarly journals A Lacustrine Glacier Retreat Sequence from the Permo-Carboniferous Dwyka Formation, Republic of South Africa

1983 ◽  
Vol 29 (103) ◽  
pp. 515-520
Author(s):  
J. N. J. Visser
Keyword(s):  
South Africa ◽  
Lacustrine Sediments ◽  
Glacier Retreat ◽  
Marine Transgression ◽  
Northern Margin ◽  
Valley Fill ◽  
Karoo Basin ◽  
Ice Retreat ◽  
Glacier Advance

Abstract The upper part of a Permo-Carboniferous glacial valley fill along the northern margin of the Karoo Basin includes glacio-lacustrine sediments. During the last glacier advance into the lake, a bedded heterogeneous diamictite facies was deposited and, on glacier retreat, a sequence of deformed siltstones with diamictite lenses and sandstone beds, varved shale and rhythmite shale was laid down. Black carbonaceous mud was deposited during the subsequent marine transgression. According to varve counts, the glacier receded from the valley over a period of 500 to 1 000 years and it is concluded that the overall ice-retreat rate during the Permo-Carboniferous deglaciation was relatively high.

scholarly journals Microbial nitrification and acidification of lacustrine sediments deduced from the nature of a sedimentary kaolin deposit in central Japan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tetsuichi Takagi ◽  
Ki-Cheol Shin ◽  
Mayumi Jige ◽  
Mihoko Hoshino ◽  
Katsuhiro Tsukimura
Keyword(s):  
Nitric Acid ◽  
Lacustrine Sediments ◽  
Kaolin Clay ◽  
Central Japan ◽  
Inland Lakes ◽  
Fe Oxidation ◽  
Stable Isotopic ◽  
Fe Hydroxide ◽  
Kaolin Deposit ◽  
Dilute Nitric Acid

AbstractKaolin deposits in the Seto-Tono district, central Japan, were formed by intense kaolinization of lacustrine arkose sediments deposited in small and shallow inland lakes in the late Miocene. Based on mineralogical and stable isotopic (Fe, C, N) studies of Motoyama kaolin deposit in the Seto area, we concluded that it was formed by microbial nitrification and acidification of lacustrine sediments underneath an inland lake. Small amounts of Fe–Ti oxides and Fe-hydroxide in the kaolin clay indicated that iron was oxidized and leached during the kaolinization. The field occurrences indicate that leached ferric iron precipitated on the bottom of the kaolin deposit as limonite crusts, and their significantly fractionated Fe isotope compositions suggest the involvement of microbial activity. The C/N ratios of most of the kaolin clay are distinctly higher than those of modern lacustrine sediment. Although, the possibility of a low-temperature hydrothermal origin of the kaolin deposit cannot be completely ruled out, it is more likely that acidification by dilute nitric acid formed from plant-derived ammonia could have caused the kaolinization, Fe oxidation and leaching. The nitrate-dependent microbial Fe oxidation is consistent with dilute nitric acid being the predominant oxidant.

scholarly journals Coeval primary and diagenetic carbonates in lacustrine sediments challenge palaeoclimate interpretations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jeremy McCormack ◽  
Ola Kwiecien
Keyword(s):  
Isotope Composition ◽  
Lacustrine Sediments ◽  
Carbon Isotope Composition ◽  
Large Variability ◽  
Oxygen And Carbon Isotope ◽  
Temperature And Precipitation ◽  
Lacustrine Carbonates ◽  
Geochemical Analyses ◽  
Mixed Nature ◽  
Water Carbonate

AbstractLakes are sensitive to climate change and their sediments play a pivotal role as environmental recorders. The oxygen and carbon isotope composition (δ18O and δ13C) of carbonates from alkaline lakes is featured in numerous studies attempting a quantitative reconstruction of rainfall, temperature and precipitation-evaporation changes. An often-overlooked challenge consists in the mineralogically mixed nature of carbonates themselves. We document a large variability of carbonate components and their respective distinct δ18O and δ13C values from sediments of Lake Van (Turkey) covering the last 150 kyr. The carbonate inventory consists of primary (1) inorganic calcite and aragonite precipitating in the surface-water, (2) biogenic calcite ostracod valves; and post-depositional phases: (3) dolomite forming in the sediment, and previously overlooked, (4) aragonite encrustations formed rapidly around decaying organic matter. We find a systematic relation between the lithology and the dominant deep-water carbonate phase formed recurrently under specific hydrological conditions. The presence of the different carbonates is never mutually exclusive, and the isotopic composition of each phase forms a distinctive cluster characteristic for the depth and timing of their formation. Our findings stretch the envelope of mechanisms forming lacustrine carbonates and highlight the urge to identify and separate carbonate components prior to geochemical analyses.

scholarly journals Factors of boreal summer latent heat flux variations over the tropical western North Pacific

2021 ◽  
Author(s):  
Yuqi Wang ◽  
Renguang Wu
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
North Pacific ◽  
High Frequency ◽  
Western North Pacific ◽  
Surface Wind ◽  
Low Frequency ◽  
Boreal Summer ◽  
Wind Intensity ◽  
Tropical Western North Pacific

AbstractSurface latent heat flux (LHF) is an important component in the heat exchange between the ocean and atmosphere over the tropical western North Pacific (WNP). The present study investigates the factors of seasonal mean LHF variations in boreal summer over the tropical WNP. Seasonal mean LHF is separated into two parts that are associated with low-frequency (> 90-day) and high-frequency (≤ 90-day) atmospheric variability, respectively. It is shown that low-frequency LHF variations are attributed to low-frequency surface wind and sea-air humidity difference, whereas high-frequency LHF variations are associated with both low-frequency surface wind speed and high-frequency wind intensity. A series of conceptual cases are constructed using different combinations of low- and high-frequency winds to inspect the respective effects of low-frequency wind and high-frequency wind amplitude to seasonal mean LHF variations. It is illustrated that high-frequency wind fluctuations contribute to seasonal high-frequency LHF only when their intensity exceeds the low-frequency wind speed under which there is seasonal accumulation of high-frequency LHF. When high-frequency wind intensity is smaller than the low-frequency wind speed, seasonal mean high-frequency LHF is negligible. Total seasonal mean LHF anomalies depend on relative contributions of low- and high-frequency atmospheric variations and have weak interannual variance over the tropical WNP due to cancellation of low- and high-frequency LHF anomalies.

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