scholarly journals Robustly quantifying seafloor anoxia using uranium isotope data from ancient marine sediments

2021 ◽  
Author(s):  
Michael Kipp ◽  
François Tissot
Keyword(s):  
Marine Sediments ◽  
Uranium Isotope ◽  
Isotope Data

scholarly journals Melting of recycled ancient crust responsible for the Gutenberg discontinuity

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Jia Liu ◽  
Naoto Hirano ◽  
Shiki Machida ◽  
Qunke Xia ◽  
Chunhui Tao ◽  
...  
Keyword(s):  
Partial Melting ◽  
Marine Sediments ◽  
Seismic Velocity ◽  
Pacific Plate ◽  
Northwest Pacific ◽  
Geochemical Evidence ◽  
Isotope Data ◽  
Deep Earth

AbstractA discontinuity in the seismic velocity associated with the lithosphere-asthenosphere interface, known as the Gutenberg discontinuity, is enigmatic in its origin. While partial mantle melts are frequently suggested to explain this discontinuity, it is not well known which factors critically regulate the melt production. Here, we report geochemical evidence showing that the melt fractions in the lithosphere-asthenosphere boundary were enhanced not only by accumulation of compacted carbonated melts related to recycled ancient marine sediments, but also by partial melting of a pyroxene-rich mantle domain related to the recycled oceanic eclogite/pyroxenites. This conclusion is derived from the first set of Mg isotope data for a suite of young petit-spot basalts erupted on the northwest Pacific plate, where a clearly defined Gutenberg discontinuity exists. Our results reveal a specific linkage between the Gutenberg discontinuity beneath the normal oceanic regions and the recycling of ancient subducted crust and carbonate through the deep Earth.

Mercury isotopes track the cause of carbon perturbations in the Ediacaran ocean

Geology ◽  
2020 ◽  
Author(s):  
Haifeng Fan ◽  
Xuewu Fu ◽  
Jack F. Ward ◽  
Runsheng Yin ◽  
Hanjie Wen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Carbon Isotope ◽  
Marine Sediments ◽  
South China ◽  
South Australia ◽  
Deep Ocean ◽  
Isotope Data ◽  
Carbonate Carbon ◽  
Terrestrial Input

The unusual carbon biogeochemical cycling that occurred in the Ediacaran (ca. 635–541 Ma) ocean may have been critical for ocean oxygenation and Ediacaran life evolution. However, the triggers of the peculiar Ediacaran carbonate carbon isotope (δ13Ccarb) excursions are not well understood. Because mercury (Hg) has a strong affinity for organic carbon, we measured Hg isotope compositions (δ202Hg and Δ199Hg) from Ediacaran marine sediments of South China and South Australia to better understand the causes of the Ediacaran δ13Ccarb excursions. During two local positive δ13Ccarb excursions in the Doushantuo Formation, gradually decreasing Δ199Hg and increasing δ202Hg trends are primarily ascribed to enhanced terrestrial input. Decreasing δ202Hg in both the Doushantuo and Wonoka Formations during the latter part of the Shuram negative δ13Ccarb excursion demonstrates the significant, and potentially widespread, contribution of upwelling Hg associated with dissolved organic carbon (Hg-DOC) from the open deep ocean. New Hg isotope data also suggest that a large Hg-DOC reservoir may have been present in the open ocean continuously from the early to mid–late Ediacaran Period (ca. 635–551 Ma), buffering ocean oxygenation at that time.

The Uranium Isotope Paleoredox Proxy

2019 ◽  
Author(s):  
Kimberly V. Lau ◽  
Stephen J. Romaniello ◽  
Feifei Zhang
Keyword(s):  
Uranium Isotope

The large superpredators’ teeth from Middle Triassic of Poland

2013 ◽  
Vol 2 (1) ◽  
pp. 91-94 ◽  
Author(s):  
Dawid Surmik ◽  
Tomasz Brachaniec
Keyword(s):  
Marine Sediments ◽  
Middle Triassic ◽  
Morphological Features ◽  
Marine Reptiles

ABSTRACT An unusual large teeth, finding from time to time in marine sediments of Muschelkalk, Silesia, Poland indicate the superpredators occurrence. According to size and morphological features the teeth are similar to archosaurs or giant marine reptiles.

Some centric diatoms (Bacillariophyta) from Neogene deposits of the Fisher Massif (Prince Charles Mountains, East Antarctica)

2011 ◽  
Vol 45 ◽  
pp. 32-49
Author(s):  
R. M. Gogorev ◽  
Z. V. Pushina
Keyword(s):  
Marine Sediments ◽  
East Antarctica ◽  
Benthic Diatoms ◽  
Detailed Data ◽  
Planktonic Algae ◽  
Centric Diatoms ◽  
Planktonic Diatom ◽  
Oceanic Species ◽  
Diatom Complexes

The richest diatom complexes have revealed due to the study of glacial-marine sediments sampled in the Fisher Massif (Prince Charles Mountains, East Antarctica) during 52nd and 53rd Russian Antarctic Expeditions (Polar Marine Geol. Survey Expedition) in 2006/07 and 2007/08. Three diatom complexes are distinguished according to different palaeoecological conditions: the planktonic one is located in the basis of the outcrop, while mixed planktonic-benthic and benthic ones being located above. The planktonic diatom complexes are dominated by two oceanic species Actinocyclus ingens (up to 8%) and Denticulopsis simonseni (up to 80%). There are 15 planktonic algae, e. g. Eucampia аntarctica, Fragilariopsis spp., Rhizosolenia spp., Rouxia antarctica, Podosira antarctica sp. nov., Stellarima microtrias; and also unknown and non-described benthic diatoms Achnanthes sp., Cocconeis spp., Rhabdonema (s. l.) spp. and Synedra (s. l.) spp. Detailed data on morphology and taxonomy of 10 centric diatoms are presented, including 3 newly described species.

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