scholarly journals Geochemical Characteristics of Late Ordovician Shales in the Upper Yangtze Platform, South China: Implications for Redox Environmental Evolution

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 710
Author(s):  
Donglin Lin ◽  
Shuheng Tang ◽  
Zhaodong Xi ◽  
Bing Zhang ◽  
Yapei Ye
Keyword(s):  
Surface Waters ◽  
Ocean Surface ◽  
Late Ordovician ◽  
Yangtze Platform ◽  
Productivity Level ◽  
High Productivity ◽  
Reactive Iron ◽  
Redox Environment ◽  
Water Conditions ◽  
Sulfate Flux

Changes to the redox environment of seawater in the Late Ordovician affect the process of organic matter enrichment and biological evolution. However, the evolution of redox and its underlying causes remain unclear. This paper analyzed the vertical variability of main, trace elements and δ34Spy from a drill core section (well ZY5) in the Upper Yangtze Platform, and described the redox conditions, paleoproductivity and paleoclimate variability recorded in shale deposits of the P. pacificus zone and M. extraordinarius zone that accumulated during Wufeng Formation. The results showed that shale from well ZY5 in Late Ordovician was deposited under oxidized water environment, and there are more strongly reducing bottom water conditions of the M. extraordinarius zone compared with the P. pacificus zone. Excess silica (SiO2(exc)) and substitution index of paleoproductivity (Y) indicated that the P. pacificus zone had higher paleoproductivity whereas the M. extraordinarius zone was lower. The high productivity level controlled O2 release in the shallow water area as well as the oxidation degree of the P. pacificus zone. The decrease of productivity and the relatively stagnant water mass of the inner Yangtze Sea controlled the formation of relatively reduced water conditions in the M. extraordinarius zone. The chemical index of alteration (CIA) results suggested that palaeoclimatic conditions changed from warm and humid to cold and dry climate from the P. pacificus to the M. extraordinarius zones in the study area. A comparative analysis of the published Fe-S-C data for the Xiushan Datianba section showed that in the P. pacificus zone of the inner Yangtze Sea, warm and humid climate conditions drove high productivity, sulphate flux and low reactive iron flux, which promoted the expansion of oxic ocean-surface waters and mid-depth euxinic waters. In the M. extraordinarius zone, the cold and dry climate with significant uplift of the Xiang’e Submarine High led to the relative sea level decline, resulting in low productivity, sulfate flux and high reactive iron flux, which promoted the expansion of the mid-depth ferruginous waters and the shrinkage of oxic ocean-surface waters. The results offered new insights into the co-evolution of continents and oceans, and explained the role of continental weathering and uplift of the Xiang’e Submarine High in the exchange of sulfate flux and nutrients in the redox environment change of inner Yangtze Sea during the Late Ordovician.

Biostratigraphy and paleobiogeography of Middle and Late Ordovician conodonts from the Langkawi Islands, northwestern peninsular Malaysia

2008 ◽  
Vol 82 (5) ◽  
pp. 957-973 ◽  
Author(s):  
Sachiko Agematsu ◽  
Katsuo Sashida ◽  
Amnan B. Ibrahim
Keyword(s):  
North Atlantic ◽  
Peninsular Malaysia ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Low Latitude ◽  
Cool Water ◽  
Middle Ordovician ◽  
Water Conditions ◽  
Unidentified Species ◽  
Assemblage Zone

The Middle and Upper Ordovician sequence of the Langkawi Islands, northwestern peninsular Malaysia, contains 20 species of conodonts belonging to 15 genera and four unidentified species, which are described and illustrated. The following four biostratigraphic zones are established for the study area: the Scolopodus striatus assemblage zone, the Periodon sp. A range zone, the Baltoniodus alobatus range zone, and the Hamarodus europaeus range zone, in ascending order. The Middle Ordovician fauna belongs to the low-latitude, warm-water Australian Province. Conodonts of the H. europaeus zone represent the HDS (Hamarodus europaeus-Dapsilodus mutatus-Scabbardella altipes) biofacies, which has been reported from the cool-water North Atlantic Faunal Region. The middle Arenigian limestones in the study area were deposited on a shallow-water shelf, whereas the late Arenigian to middle Darriwilian limestones formed in hemipelagic deeper-water conditions on an outer shelf or slope.

scholarly journals Upper ocean vertical supply: A neglected primary factor controlling the distribution of neodymium concentrations of open ocean surface waters?

2013 ◽  
Vol 118 (8) ◽  
pp. 3887-3894 ◽  
Author(s):  
Tian-Yu Chen ◽  
Johannes Rempfer ◽  
Martin Frank ◽  
Roland Stumpf ◽  
Mario Molina-Kescher
Keyword(s):  
Surface Waters ◽  
Ocean Surface ◽  
Open Ocean ◽  
Primary Factor ◽  
Upper Ocean

scholarly journals PENJADWALAN PERALATAN UNTUK MENINGKATKAN KINERJA SISTEM MANUFAKTUR DENGAN PENDEKATAN SIMULASI SISTEM DISKRIT

2017 ◽  
Author(s):  
Abdurrozzaq Hasibuan
Keyword(s):  
Development Strategy ◽  
Real System ◽  
Product Cycle ◽  
Manufacturing Companies ◽  
Productivity Level ◽  
The Real ◽  
High Productivity ◽  
Work In Process ◽  
System P ◽  
System Variables

Facing the thight business competition era, the manufacturing companies have to development their industrial system preformances to the high productivity level. This paper explain three manufacturing system indicator; amount of standart output in a periode of time, product cycle time, and the amount of work in process (unfinish) product. Those three indicators will be viewed as a result of tools and production machine resources allocation in each work station.The Discrete system simulation was used to represent the real system that is examined. This method can give a details information about the characteristic of each system variables when try to make an experiment to improve the system performances without bothering and interrupt the real system it self. This situation will exactly reduce the unpredictable risk when implement the development strategy in the real system.

scholarly journals The iron budget in ocean surface waters in the 20th and 21st centuries: projections by the Community Earth System Model version 1

2013 ◽  
Vol 10 (5) ◽  
pp. 8505-8559 ◽  
Author(s):  
K. Misumi ◽  
K. Lindsay ◽  
J. K. Moore ◽  
S. C. Doney ◽  
F. O. Bryan ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Surface Waters ◽  
Ocean Surface ◽  
Equatorial Pacific ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Iron Supply ◽  
Eastern Equatorial Pacific ◽  
Community Earth System Model

Abstract. We investigated the simulated iron budget in ocean surface waters in the 1990s and 2090s using the Community Earth System Model version 1 and the Representative Concentration Pathway 8.5 future CO2 emission scenario. We assumed that exogenous iron inputs did not change during the whole simulation period; thus, iron budget changes were attributed solely to changes in ocean circulation and mixing in response to projected global warming. The model simulated the major features of ocean circulation and dissolved iron distribution for the present climate reasonably well. Detailed iron budget analysis revealed that roughly 70% of the iron supplied to surface waters in high-nutrient, low-chlorophyll (HNLC) regions is contributed by ocean circulation and mixing processes, but the dominant supply mechanism differed in each HNLC region: vertical mixing in the Southern Ocean, upwelling in the eastern equatorial Pacific, and deposition of iron-bearing dust in the subarctic North Pacific. In the 2090s, our model projected an increased iron supply to HNLC surface waters, even though enhanced stratification was predicted to reduce iron entrainment from deeper waters. This unexpected result could be attributed largely to changes in the meridional overturning and gyre-scale circulations that intensified the advective supply of iron to surface waters, especially in the eastern equatorial Pacific. The simulated primary and export productions in the 2090s decreased globally by 6% and 13%, respectively, whereas in the HNLC regions, they increased by 11% and 6%, respectively. Roughly half of the elevated production could be attributed to the intensified iron supply. The projected ocean circulation and mixing changes are consistent with recent observations of responses to the warming climate and with other Coupled Model Intercomparison Project model projections. We conclude that future ocean circulation and mixing changes will likely elevate the iron supply to HNLC surface waters and will potentially buffer future reductions in ocean productivity. External inputs of iron to the oceans are likely to be modified with climate change. Future work must incorporate robust estimates of these processes affecting the marine iron cycle.

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