scholarly journals Carbon and nitrogen isotope evidence for widespread presence of anoxic intermediate waters before and during the Permian-Triassic mass extinction

2021 ◽  
Author(s):  
Baojin Wu ◽  
Genming Luo ◽  
Michael M. Joachimski ◽  
Paul B. Wignall ◽  
Lidan Lei ◽  
...  
Keyword(s):  
Shallow Water ◽  
Water Column ◽  
Water Depth ◽  
Mass Extinction ◽  
Isotope Composition ◽  
Nitrogen Isotope ◽  
Intermediate Water ◽  
Negative Shift ◽  
Intermediate Waters ◽  
Direct Killing

The largest mass extinction since the advent of animals occurred during the Permian-Triassic (P-Tr) transition, ca. 252 Ma, and is commonly attributed to the eruption of the Siberian Traps large igneous province. However, the direct killing mechanism is still debated. In this study, we investigated marine redox conditions of the intermediate water column that most organisms inhabit with special attention to the time interval before the onset of the mass extinction. The carbon isotope composition of carbonate and organic carbon (δ13Ccarb and δ13Corg) as well as the nitrogen isotope composition of bulk nitrogen (δ15N) were analyzed in four P-Tr boundary sequences (Zhongli, Jianshi, Ganxi, and Chaotian sections), which record a transect from a shallow water carbonate platform to a deep water, lower ramp slope in South China. δ13Ccarb shows a distinct negative shift in all sections and displays a clear, 2−4‰, decreasing gradient accompanying an increase in water depth both before and after the mass extinction. A distinct negative shift in δ15N is observed in the shallow water Zhongli section, whereas a minor negative shift is present in the three deeper water sections. Before the mass extinction, the δ15N values from shallow water sections are higher than those from deeper waters. The low δ15N values close to 0‰ in deeper water sections suggest that microbial nitrogen fixation was the predominant source of biologically available nitrogen before the onset of the mass extinction. Thus, the water depth- dependent gradient in δ13Ccarb and δ15N suggests that an oxygen-deficient intermediate water column was already present before the mass extinction. The uniform δ15N values around 0‰ accompanying the onset of the mass extinction reveal that anoxic intermediate waters expanded into shallow waters. Meanwhile, the distinct positive shift in δ13Corg observed in upper ramp slope sections, i.e., the Jianshi and Ganxi sections, suggests that a euxinic photic zone was at least episodically present in the earliest Triassic. The temporal coincidence between the expansion of intermediate water column anoxia and the onset of the P-Tr mass extinction supports the hypothesis that marine anoxia was a direct killing mechanism.

Validation of Wave Propagation in Numerical Wave Tanks

2005 ◽  
Author(s):  
Tim Bunnik ◽  
Rene´ Huijsmans
Keyword(s):  
Shallow Water ◽  
Model Test ◽  
Water Depth ◽  
Linear Potential ◽  
Intermediate Water ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Type Wave ◽  
Wave Generator ◽  
Numerical Wave

During the last few years there has been a strong growth in the availability and capabilities of numerical wave tanks. In order to assess the accuracy of such methods, a validation study was carried out. The study focuses on two types of numerical wave tanks: 1. A numerical wave tank based a non-linear potential flow algorithm. 2. A numerical wave tank based on a Volume of Fluid algorithm. The first algorithm uses a structured grid with triangular elements and a surface tracking technique. The second algorithm uses a structured, Cartesian grid and a surface capturing technique. Validation material is available by means of waves measured at multiple locations in two different model test basins. The first method is capable of generating waves up to the break limit. Wave absorption is therefore modeled by means of a numerical beach and not by mean of the parabolic beach that is used in the model basin. The second method is capable of modeling wave breaking. Therefore, the parabolic beach in the model test basin can be modeled and has also been included. Energy dissipation therefore takes place according to physics which are more related to the situation in the model test basin. Three types of waves are generated in the model test basin and in the numerical wave tanks. All these waves are generated on basin scale. The following waves are considered: 1. A scaled 100-year North-Sea wave (Hs = 0.24 meters, Tp = 2.0 seconds) in deep water (5 meters). 2. A scaled operational wave (Hs = 0.086 meters, Tp = 1.69 seconds) at intermediate water depth (0.86 meters) generated by a flap-type wave generator. 3. A scaled operational wave (Hs = 0.046 meters, Tp = 1.2 seconds) in shallow water (0.35 meters) generated by a piston-type wave generator. The waves are generated by means of a flap or piston-type wave generator. The motions of the wave generator in the simulations (either rotational or translational) are identical to the motions in the model test basin. Furthermore, in the simulations with intermediate water depth, the non-flat contour of the basin bottom (ramp) is accurately modeled. A comparison is made between the measured and computed wave elevation at several locations in the basin. The comparison focuses on: 1. Reflection characteristics of the model test basin and the numerical wave tanks. 2. The accuracy in the prediction of steep waves. 3. Second order effects like set-down in intermediate and shallow water depth. Furthermore, a convergence study is presented to check the grid independence of the wave tank predictions.

scholarly journals Genesis and Evolution of Ferromanganese Crusts from the Summit of Rio Grande Rise, Southwest Atlantic Ocean

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 349 ◽  
Author(s):  
Mariana Benites ◽  
James R. Hein ◽  
Kira Mizell ◽  
Terrence Blackburn ◽  
Luigi Jovane
Keyword(s):  
Atlantic Ocean ◽  
Shallow Water ◽  
Water Column ◽  
Rio Grande ◽  
Intermediate Water ◽  
Mode Water ◽  
Southwest Atlantic ◽  
Ferromanganese Crusts ◽  
Depositional Processes ◽  
Water Depths

The Rio Grande Rise (RGR) is a large elevation in the Atlantic Ocean and known to host potential mineral resources of ferromanganese crusts (Fe–Mn), but no investigation into their general characteristics have been made in detail. Here, we investigate the chemical and mineralogical composition, growth rates and ages of initiation, and phosphatization of relatively shallow-water (650–825 m) Fe–Mn crusts dredged from the summit of RGR by using computed tomography, X-ray diffraction, 87Sr/86Sr ratios, U–Th isotopes, and various analytical techniques to determine their chemical composition. Fe–Mn crusts from RGR have two distinct generations. The older one has an estimated age of initiation around 48–55 Ma and was extensively affected by post-depositional processes under suboxic conditions resulting in phosphatization during the Miocene (from 20 to 6.8 Ma). As a result, the older generation shows characteristics of diagenetic Fe–Mn deposits, such as low Fe/Mn ratios (mean 0.52), high Mn, Ni, and Li contents and the presence of a 10 Å phyllomanganate, combined with the highest P content among crusts (up to 7.7 wt %). The younger generation is typical of hydrogenetic crusts formed under oxic conditions, with a mean Fe/Mn ratio of 0.75 and mean Co content of 0.66 wt %, and has the highest mean contents of Bi, Nb, Ni, Te, Rh, Ru, and Pt among crusts formed elsewhere. The regeneration of nutrients from local biological productivity in the water column is the main source of metals to crusts, providing mainly metals that regenerate rapidly in the water column and are made available at relatively shallow water depths (Ni, As, V, and Cd), at the expense of metals of slower regeneration (Si and Cu). Additionally, important contributions of nutrients may derive from various water masses, especially the South Atlantic Mode Water and Antarctic Intermediate Water (AAIW). Bulk Fe–Mn crusts from the summit of RGR plateau are generally depleted in metals considered of greatest economic interest in crusts like Co, REE, Mo, Te, and Zr, but are the most enriched in the critical metals Ni and Li compared to other crusts. Further investigations are warranted on Fe–Mn crusts from deeper-water depths along the RGR plateau and surrounding areas, which would less likely be affected by phosphatization.

scholarly journals Long-Term Changes in the Water Mass Properties in the Balearic Channels Over the Period 1996–2019

2021 ◽  
Vol 8 ◽  
Author(s):  
Manuel Vargas-Yáñez ◽  
Mélanie Juza ◽  
M. Carmen García-Martínez ◽  
Francina Moya ◽  
Rosa Balbín ◽  
...  
Keyword(s):  
Water Column ◽  
Water Mass ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Intermediate Water ◽  
Deep Waters ◽  
Mass Properties ◽  
Long Term Changes ◽  
Intermediate Waters

The analysis of a 24-year time series of Conductivity-Temperature-Depth (CTD) casts collected in the Balearic Channels (1996–2019) has allowed detecting and quantifying long-term changes in water mass properties in the Western Mediterranean. For the complete period, the intermediate waters have experienced warming and salting at rates of 1.4°C/100yr and 0.3–0.6/100yr for the Western Intermediate Water, and 1°C/100yr and 0.3–0.4/100yr for the Levantine Intermediate Water. The density of these two water masses has not changed. The deep waters, defined as those denser than 29.1 kg/m3, showed positive trends in temperature, salinity, and density (0.8°C/100yr, 0.2/100yr, and 0.02 kg.m–3/100yr, respectively). The high temporal variability of the upper layer makes the detection of long-term changes more difficult. Nevertheless, combining CTD data with temperature data from the oceanographic station at L’Estartit and simulated data from the NCEP/NCAR reanalysis, it can be established that the Atlantic Water increased its temperature at a rate of 2.1–2.8°C/100yr and likely its salinity at a rate of 0.6/100yr. The water column absorbed heat at a rate equivalent to 1–1.2 W/m2. All these trends are much higher than those reported in previous works (more than double in some cases). The warming of the water column produced an increase in the thermosteric component of sea level. However, this increase was compensated by the decrease in the halosteric component. Besides these changes, other alterations related to the Western Mediterranean Transition have been observed over shorter periods. The temperature and salinity of the intermediate waters increased before the winter of 2004/2005 and then the temperature and salinity of the deep waters increased dramatically in 2005. The density of the deep water reached values unprecedented before 2005. Deep and intermediate waters were uplifted by the presence of such dense deep waters. The arrival of warmer and saltier intermediate waters from the Eastern Mediterranean is also observed, mainly after 2010.

scholarly journals Oxygen and carbon isotope composition of modern planktic foraminifera and near-surface waters in the Fram Strait (Arctic Ocean) – a case-study

2014 ◽  
Vol 11 (6) ◽  
pp. 8635-8672
Author(s):  
T. Pados ◽  
R. F. Spielhagen ◽  
D. Bauch ◽  
H. Meyer ◽  
M. Segl
Keyword(s):  
Water Column ◽  
Carbon Isotope ◽  
Water Depth ◽  
Isotope Composition ◽  
Environmental Parameters ◽  
Early Summer ◽  
Sediment Surface ◽  
Fram Strait ◽  
Planktic Foraminifera ◽  
Near Surface

Abstract. The upper 500 m of the water column and the sediment surface along an E–W transect in the Fram Strait were sampled for recent planktic foraminifera. The δ18O and δ13C values of the tests are compared to the stable isotope composition of water samples taken from the same depths, and related to the characteristics of the water column. The polar species Neogloboquadrina pachyderma (sin.) clearly dominates the species assemblage in the Fram Strait in the early summer, while the subpolar Turborotalita quinqueloba accounts only for 5–23%. In this area the average depth of calcification of N. pachyderma (sin.) lies between 70–150m water depth, T. quinqueloba shows a similar range with 50–120 m water depth. The δ18O values of N. pachyderma (sin.) show an average vital effect of about −1.5‰ compared to calculated equilibrium calcite values. Except for the upper ~ 75 m, the vertical profiles of δ13C of the net-sampled shells are nearly parallel to the values measured in the water column with an average offset of −1.6‰ and −3.6‰ for N. pachyderma (sin.) and T. quinqueloba, respectively. The discrepancy found in the upper ~ 75 m might indicate the influence of the "carbonate ion effect" on the carbon isotope incorporation in the tests. Oxygen and carbon isotopes from the sediment surface yield higher values than those from the water column for both species. This may be because specimens from the water column reflect a modern snapshot only, while tests from surface sediments record environmental parameters from the past ~ 1000 years.

scholarly journals Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals

2017 ◽  
Vol 13 (1) ◽  
pp. 17-37 ◽  
Author(s):  
Quentin Dubois-Dauphin ◽  
Paolo Montagna ◽  
Giuseppe Siani ◽  
Eric Douville ◽  
Claudia Wienberg ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Mediterranean Sea ◽  
Water Depth ◽  
Cold Water ◽  
Western Mediterranean ◽  
Intermediate Water ◽  
Western Mediterranean Sea ◽  
Deep Waters ◽  
Balearic Sea ◽  
Intermediate Waters

Abstract. We present the neodymium isotopic composition (εNd) of mixed planktonic foraminifera species from a sediment core collected at 622 m water depth in the Balearic Sea, as well as εNd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442 m water depth in the Alboran Sea and at 414 m depth in the southern Sardinian continental margin. The aim is to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 kyr. Planktonic (Globigerina bulloides) and benthic (Cibicidoides pachyderma) foraminifera from the Balearic Sea were also analyzed for stable oxygen (δ18O) and carbon (δ13C) isotopes. The foraminiferal and coral εNd values from the Balearic and Alboran seas are comparable over the last  ∼  13 kyr, with mean values of −8.94 ± 0.26 (1σ; n =  24) and −8.91 ± 0.18 (1σ; n =  25), respectively. Before 13 ka BP, the foraminiferal εNd values are slightly lower (−9.28 ± 0.15) and tend to reflect higher mixing between intermediate and deep waters, which are characterized by more unradiogenic εNd values. The slight εNd increase after 13 ka BP is associated with a decoupling in the benthic foraminiferal δ13C composition between intermediate and deeper depths, which started at  ∼  16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic εNd from deep waters. The CWC from the Sardinia Channel show a much larger scatter of εNd values, from −8.66 ± 0.30 to −5.99 ± 0.50, and a lower average (−7.31 ± 0.73; n =  19) compared to the CWC and foraminifera from the Alboran and Balearic seas, indicative of intermediate waters sourced from the Levantine basin. At the time of sapropel S1 deposition (10.2 to 6.4 ka), the εNd values of the Sardinian CWC become more unradiogenic (−8.38 ± 0.47; n =  3 at  ∼  8.7 ka BP), suggesting a significant contribution of intermediate waters originated from the western basin. We propose that western Mediterranean intermediate waters replaced the Levantine Intermediate Water (LIW), and thus there was a strong reduction of the LIW during the mid-sapropel ( ∼  8.7 ka BP). This observation supports a notable change of Mediterranean circulation pattern centered on sapropel S1 that needs further investigation to be confirmed.

scholarly journals Oxygen and carbon isotope composition of modern planktic foraminifera and near-surface waters in the Fram Strait (Arctic Ocean) – a case study

2015 ◽  
Vol 12 (6) ◽  
pp. 1733-1752 ◽  
Author(s):  
T. Pados ◽  
R. F. Spielhagen ◽  
D. Bauch ◽  
H. Meyer ◽  
M. Segl
Keyword(s):  
Water Column ◽  
Carbon Isotope ◽  
Water Depth ◽  
Isotope Composition ◽  
Environmental Parameters ◽  
Early Summer ◽  
Sediment Surface ◽  
Fram Strait ◽  
Planktic Foraminifera ◽  
Near Surface

Abstract. The upper 500 m of the water column and the sediment surface along an E–W transect in the Fram Strait were sampled for recent planktic foraminifera. The δ18O and δ13C values of the tests are compared to the stable isotope composition of the water samples taken from the same depths, and related to the characteristics of the water column. The polar species Neogloboquadrina pachyderma clearly dominates the species assemblage in the Fram Strait in the early summer, while the subpolar Turborotalita quinqueloba accounts only for 5–23%. In this area the average depth of calcification of N. pachyderma lies between 70–150 m water depth, T. quinqueloba shows a similar range with 50–120 m water depth. The δ18O values of N. pachyderma show an average vital effect of about −1.5‰ compared to calculated equilibrium calcite values. Except for the upper ∼75 m, the vertical profiles of δ13C of the net-sampled shells are nearly parallel to the values measured in the water column with an average offset of −1.6‰ and −3.6‰ for N. pachyderma and T. quinqueloba, respectively. The discrepancy found in the upper ~75 m might indicate an influence of the "carbonate ion effect" on the carbon isotope incorporation in the tests. Oxygen and carbon isotopes from the sediment surface yield higher values than those from the water column for both species. This may be because specimens from the water column reflect a modern snapshot only, while tests from surface sediments record environmental parameters from the past ~1000 years.

Comparison of the performance of oscillating water column devices based on arrangements of water columns

2020 ◽  
Vol 14 (3) ◽  
pp. 7082-7093
Author(s):  
Jahirwan Ut Jasron ◽  
Sudjito Soeparmani ◽  
Lilis Yuliati ◽  
Djarot B. Darmadi
Keyword(s):  
Wave Propagation ◽  
Water Column ◽  
Water Depth ◽  
Graphical Form ◽  
Wave Power ◽  
Oscillating Water Column ◽  
Power Absorption ◽  
Water Columns ◽  
Single Column ◽  
Parallel Arrangement

The hydrodynamic performance of oscillating water column (OWC) depends on the depth of the water, the size of the water column and its arrangement, which affects the oscillation of the water surface in the column. An experimental method was conducted by testing 4 water depths with wave periods of 1-3 s. All data recorded by the sensor is then processed and presented in graphical form. The research focused on analyzing the difference in wave power absorption capabilities of the three geometric types of OWC based on arrangements of water columns. The OWC devices designed as single water column, the double water column in a series arrangement which was perpendicular to the direction of wave propagation, and double water column in which the arrangement of columns was parallel to the direction of wave propagation. This paper discussed several factors affecting the amount of power absorbed by the device. The factors are the ratio of water depth in its relation to wavelength (kh) and the inlet openings ratio (c/h) of the devices. The test results show that if the water depth increases in the range of kh 0.7 to 0.9, then the performance of the double chamber oscillating water column (DCOWC) device is better than the single chamber oscillating water column (SCOWC) device with maximum efficiency for the parallel arrangement 22,4%, series arrangement 20.8% and single column 20.7%. However, when referring to c/h, the maximum energy absorption efficiency for a single column is 27.7%, double column series arrangement is 23.2%, and double column parallel arrangement is 29.5%. Based on the results of the analysis, DCOWC devices in parallel arrangement showed the ability to absorb better wave power in a broader range of wave frequencies. The best wave of power absorption in the three testing models occurred in the wave period T = 1.3 seconds.

Carbon and Nitrogen Isotope Composition of the Wood of Pinus sylvestris, Betula pendula and Populus tremula

2020 ◽  
Vol 54 (8) ◽  
pp. 819-824
Author(s):  
P. Yu. Voronin ◽  
V. A. Mukhin ◽  
T. A. Velivetskaya ◽  
A. V. Ignatiev ◽  
Vl. V. Kuznetsov
Keyword(s):  
Pinus Sylvestris ◽  
Betula Pendula ◽  
Isotope Composition ◽  
Nitrogen Isotope ◽  
Populus Tremula ◽  
Carbon And Nitrogen ◽  
Nitrogen Isotope Composition
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