scholarly journals Multiple Sulfur Isotope Geochemistry during the Permian-Triassic Transition

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 327
Author(s):  
Masafumi Saitoh
Keyword(s):  
Sulfur Isotope ◽  
Isotope Geochemistry ◽  
Shallow Marine ◽  
Biodiversity Crisis ◽  
Deep Waters ◽  
Depositional Settings ◽  
Isotope Record ◽  
Isotope Studies ◽  
Permian Mass Extinction ◽  
Isotopic Signal

The end-Permian mass extinction was the largest biodiversity crisis in the Phanerozoic. Based on characteristic negative ∆33S signals of sedimentary pyrite, previous multiple sulfur isotope studies suggested shoaling of anoxic/sulfidic deep-waters onto a shelf, leading to the shallow-marine extinction. However, the validity of this shoaling model has been controversial. I compiled previously-reported multiple sulfur isotope records during the Permian-Triassic transition interval, and examined a stratigraphic relationship between the extinction horizon, redox oscillation in the depositional settings, and the multiple sulfur isotope record in each studied section. The compilation shows that the negative ∆33S signals do not correspond clearly to the extinction horizon or to the benthic anoxia/euxinia in the studied sections. The compilation also documents that the multiple sulfur isotope records during the Permian-Triassic transition are substantially variable, and that the negative ∆33S signals were observed in various types of sediments including shallow-marine carbonates, carbonates/siltstones of relatively deep-water facies, and abyssal deep-sea cherts. Those observations allow me to infer that the negative ∆33S signal is not a robust indicator of shoaling. Rather, this isotopic signal may reflect substantial sulfur isotope heterogeneity in the sediments controlled by local factors.

When bivalves took over the world

Paleobiology ◽  
2007 ◽  
Vol 33 (3) ◽  
pp. 397-413 ◽  
Author(s):  
Margaret L. Fraiser ◽  
David J. Bottjer
Keyword(s):  
Mass Extinction ◽  
Arms Race ◽  
Steady Increase ◽  
Early Triassic ◽  
Environmental Distribution ◽  
Biodiversity Crisis ◽  
Marine Communities ◽  
The World ◽  
Mesozoic Marine Revolution ◽  
Permian Mass Extinction

AbstractThe end-Permian mass extinction is commonly portrayed not only as a massive biodiversity crisis but also as the time when marine benthic faunas changed from the Paleozoic Fauna, dominated by rhynchonelliform brachiopod taxa, to the Modern Fauna, dominated by gastropod and bivalve taxa. After the end-Permian mass extinction, scenarios involving the Mesozoic Marine Revolution portray a steady increase in numerical dominance by these benthic molluscs as largely due to the evolutionary effects of an “arms race.” We report here a new global paleoecological database from study of shell beds that shows a dramatic geologically sudden earliest Triassic takeover by bivalves as numerical dominants in level-bottom benthic marine communities, which continued through the Early Triassic. Three bivalve genera were responsible for this switch, none of which has any particular morphological features to distinguish it from many typical Paleozoic bivalve genera. The numerical success of these Early Triassic bivalves cannot be attributed to any of the well-known morphological evolutionary innovations of post-Paleozoic bivalves that characterize the Mesozoic Marine Revolution. Rather, their ability to mount this takeover most likely was due to the large extinction of rhynchonelliform brachiopods during the end-Permian mass extinction and aided by their environmental distribution and physiological characteristics that enabled them to thrive during periods of oceanic and atmospheric stress during the Permian/Triassic transition.

Sulfur isotopes in diamonds reveal differences in continent construction

Science ◽  
2019 ◽  
Vol 364 (6438) ◽  
pp. 383-385 ◽  
Author(s):  
Karen V. Smit ◽  
Steven B. Shirey ◽  
Erik H. Hauri ◽  
Richard A. Stern
Keyword(s):  
Sulfur Isotope ◽  
Sulfur Isotopes ◽  
West African ◽  
Diamond Growth ◽  
Mantle Lithosphere ◽  
Continental Lithosphere ◽  
Slave Craton ◽  
Tectonic Processes ◽  
Isotope Record ◽  
Diamond Inclusions

Neoproterozoic West African diamonds contain sulfide inclusions with mass-independently fractionated (MIF) sulfur isotopes that trace Archean surficial signatures into the mantle. Two episodes of subduction are recorded in these West African sulfide inclusions: thickening of the continental lithosphere through horizontal processes around 3 billion years ago and reworking and diamond growth around 650 million years ago. We find that the sulfur isotope record in worldwide diamond inclusions is consistent with changes in tectonic processes that formed the continental lithosphere in the Archean. Slave craton diamonds that formed 3.5 billion years ago do not contain any MIF sulfur. Younger diamonds from the Kaapvaal, Zimbabwe, and West African cratons do contain MIF sulfur, which suggests craton construction by advective thickening of mantle lithosphere through conventional subduction-style horizontal tectonics.

scholarly journals Deciphering tectonic, eustatic and surface controls on the 20 Ma-old Burdigalian transgression recorded in the Upper Marine Molasse in Switzerland

2019 ◽  
Author(s):  
Philippos Garefalakis ◽  
Fritz Schlunegger
Keyword(s):  
Sea Level ◽  
Depositional Environments ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Crustal Material ◽  
Molasse Basin ◽  
Shallow Marine ◽  
Depositional Settings ◽  
Stratigraphic Architecture ◽  
Aar Massif

Abstract. The stratigraphic architecture of the Swiss Molasse basin reveals crucial information about the basin’s geometry, its evolution and the processes leading to the deposition of the clastic material. Nevertheless, the formation of the Upper Marine Molasse (OMM) and the controls on the related Burdigalian transgression are not fully understood yet. During these times, from c. 20 to 17 Ma, the Swiss Molasse basin was partly flooded by a peripheral shallow marine sea, striking SW – NE. We proceeded through detailed sedimentological and stratigraphic examinations of several sites across the entire Swiss Molasse basin in order to deconvolve the stratigraphic signals related surface and tectonic controls. Surface-related signals include stratigraphic responses to changes in eustatic sea level and sediment fluxes, while the focus on crustal-scale processes lies on the uplift of the Aar-massif at c. 20 Ma. Field examinations show, that the evolution of the Burdigalian seaway was characterized by (i) shifts in the depositional settings, (ii) changes in discharge directions, a deepening and widening of the basin, and (iv) phases of erosion and non-deposition. We relate these changes in the stratigraphic records to a combination of surface and tectonic controls at various scales. In particular, roll-back subduction of the European mantle lithosphere, delamination of crustal material and the associated rise of the Aar-massif most likely explain the widening of the basin particular at distal sites. In addition, the uplift of the Aar-massif was likely to have shifted the patterns of surface loads. These mechanisms could have caused a flexural adjustment of the foreland plate underneath the Molasse basin, which we use as mechanism to explain the establishment of distinct depositional environments and particularly the formation of subtidal-shoals where a lateral bulge is expected. In the Alpine hinterland, these processes occurred simultaneously with a period of fast tectonic exhumation accomplished through slip along the Simplon detachment fault, with the consequence that sediment flux to the basin decreased. It is possible that this reduction in sediment supply contributed to the establishment of marine conditions in the Swiss Molasse basin and thus amplified the effect related to the tectonically controlled widening of the basin. Because of the formation of shallow marine conditions, subtle changes in the eustatic sea level contributed to the occurrence several hiatus that chronicle periods of erosion and non-sedimentation. While these mechanisms are capable of explaining the establishment of the Burdigalian seaway and the formation of distinct sedimentological niches in the Swiss Molasse basin, the drainage reversal during OMM-times possibly requires a change in the tectonic processes at the slab scale. We conclude that sedimentological records can be used to decipher surface controls and lithospheric-scale processes in orogens from the stratigraphic record, provided that a detailed sedimentological and chronological database is available.

Pyrite trace-element and sulfur isotope geochemistry of paleo-mesoproterozoic McArthur Basin: Proxy for oxidative weathering

2019 ◽  
Vol 104 (9) ◽  
pp. 1256-1272 ◽  
Author(s):  
Indrani Mukherjee ◽  
Ross R. Large ◽  
Stuart Bull ◽  
Daniel G. Gregory ◽  
Aleksandr S. Stepanov ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Sulfur Isotope ◽  
Gradual Increase ◽  
Isotope Geochemistry ◽  
Atmospheric Oxygen ◽  
Black Shales ◽  
Elemental Ratios ◽  
System A ◽  
Icp Ms

Abstract Redox-sensitive trace elements and sulfur isotope compositions obtained via in situ analyses of sedimentary pyrites from marine black shales are used to track atmosphere-ocean redox conditions between ∼1730 and ∼1360 Ma in the McArthur Basin, northern Australia. Three black shale formations within the basin (Wollogorang Formation 1730 ± 3 Ma, Barney Creek Formation 1640 ± 3 Ma, and Upper Velkerri Formation 1361 ± 21 Ma) display systematic stratigraphic variations in pyrite trace-element compositions obtained using LA-ICP-MS. The concentrations of several trace elements and their ratios, such as Se, Zn, Se/Co, Ni/Co, Zn/Co, Mo/Co, Se/Bi, Zn/Bi, Ni/Bi, increase from the stratigraphically lower Wollogorang Formation to the Upper Velkerri Formation. Cobalt, Bi, Mo, Cu, and Tl show a consistent decrease in abundance while Ni, As, and Pb show no obvious trends. We interpret these trace element trends as a response to the gradual increase of oxygen in the atmosphere-ocean system from ∼1730 to 1360 Ma. Elements more mobile during erosion under rising atmospheric oxygen show an increase up stratigraphy (e.g., Zn, Se), whereas elements that are less mobile show a decrease (e.g., Co, Bi). We also propose the increase of elemental ratios (Se/Co, Ni/Co, Zn/Co, Mo/Co, Ni/Bi, and Zn/Bi) up stratigraphy are strong indicators of atmospheric oxygenation. Sulfur isotopic compositions of marine pyrite (δ34Spyrite) from these formations, obtained using SHRIMP-SI, are highly variable, with the Wollogorang Formation exhibiting less variation (δ34S = –29.4 to +9.5‰; mean –5.03‰) in comparison to the Barney Creek (δ34S = –13.8 to +41.8‰; mean +19.88‰) and Velkerri Formations (δ34S = –14.2 to +52.8‰; mean +26.9‰). We propose that the shift in mean δ34S to heavier values up-section corresponds to increasing deep water oxygenation from ∼1730 to 1360 Ma. Incursion of oxygenated waters possibly caused a decrease in the areal extent of anoxic areas, at the same time, creating a possibly efficient reducing system. A stronger reducing system caused the δ34S of the sedimentary pyrites to become progressively heavier. Interestingly, heavy δ34S in pyrites overlaps with the increase in the concentration of certain trace elements (and their ratios) in sedimentary pyrites (Se, Zn, Se/Co, Ni/Co, Zn/Co, Mo/Co, Ni/Bi, and Zn/Bi). This study concludes that there was a gradual increase of atmospheric oxygen accompanied by ocean oxygenation through the first ∼400 million years of the Boring Billion (1800–1400 Ma) in the McArthur Basin.

Sulfur Isotope Geochemistry of Sn–Polymetallic Depositsin Dafulou District of Guangxi Province, China

2012 ◽  
Vol 455-456 ◽  
pp. 1345-1349
Author(s):  
Yong Sheng Cheng
Keyword(s):  
Sulfur Isotope ◽  
Isotope Geochemistry ◽  
Guangxi Province ◽  
The West ◽  
Ore Deposit ◽  
The World ◽  
Long Time ◽  
Mineralization Age ◽  
Deposit Model ◽  
Polymetallic Ore

The Dachang tin-polymetallic ore deposit is one of the largest Sn ore deposit in the world. For a long time, the Danchi mineralization belt was studied from different perspective, i.e., the mineralization age, the ore source, the deposit model, etc. In fact, the contradistinction of the three mineralization belts has an important macroscopic significance for deepen the genetic mechanism of the Danchi mineralization belt. In the Changpo ore deposit of the west mineralization belt, besides three δ34S values (+4.794, +2.31, +2.6), the δ34S values belong to negative value, yet in the Lamo ore deposit of the middle mineralization belt, most of the δ34S values show positive besides two sulfur isotope sample (δ34S=－0.36, －1.6). But in the Dafulou ore deposit of the east mineralization belt, the δ34S values range from negative value to positive value. So there are only same ore resource partly for the Lamo ore deposit and the Changpo ore deposit. Overall, the ore source of the Dafulou ore deposit is more extensive than other ore deposit, and shares the same ore source with the other ore deposit.

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