scholarly journals Assessing controls on organic matter enrichments in hemipelagic homogenous marls of the Cretaceous Vocontian Basin (France): an unexpected variability observed from multiple organic-rich levels

2022 ◽  
Author(s):  
Alexis Caillaud ◽  
Melesio Quijada ◽  
Stephan R. Hlohowskyj ◽  
Anthony Chappaz ◽  
Viviane Bout-Roumazeilles ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Sea Level ◽  
Water Productivity ◽  
The Other ◽  
Redox Conditions ◽  
Accumulation Rates ◽  
High Productivity ◽  
Anoxic Events ◽  
Parameter Approach

The Marnes Bleues Formation from the Vocontian Basin (Southeastern France) shows many organic rich levels, some concomitant to oceanic anoxic events OAE1a and OAE1b. These organic-rich levels are scattered through a thick homogeneous succession of marls, poor in organic matter (OM). Through a multi-parameter approach, the organic-rich levels from the Aptian-Albian were characterized. Our results show that all OM-rich levels exhibit variable characteristics, such as OM nature (marine vs. continental), sedimentation and accumulation rates, redox conditions, surface-water productivity and relative sea level, but they all show low to modest enrichments in OM. Furthermore, all the levels share in common the fact that they formed under conditions of normal to low productivity and oxic to suboxic conditions. Thus, our results strongly suggest that, in the absence of high productivity and anoxic bottom conditions, the other factors reputed to favor OM accumulation only led to sporadic and low enrichments in organic contents. It is as if such factors could only enhance OM accumulation but could not induce it alone. What was true for the Vocontian Basin may be extended to other settings, regardless of their time of deposition or location.

Monsoon variability during Mid Pliocene Warm Period: Evidence from oceanic denitrification at eastern Arabian Sea

2021 ◽  
Author(s):  
Padmasini Behera ◽  
Manish Tiwari
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Water Column ◽  
Arabian Sea ◽  
Water Productivity ◽  
Warm Period ◽  
Late Pliocene ◽  
High Productivity ◽  
Future Global Warming ◽  
Eastern Arabian Sea

<p>The variability of the South Asian Monsoon (SoAM) in warmer climatic conditions is not established yet. The Mid-Pliocene Warm Period (MPWP, 3.264 to 3.025 ma) is the most recent such event when the boundary conditions were similar to present with similar CO<sub>2</sub> concentration (more than 400 ppmv) and temperature (2-3°C higher than present). It presents the best analogue for understanding the impacts of future global warming on SoAM. The high-resolution study of denitrification from the eastern Arabian Sea can provide an insight into the SoAM variability during MPWP. Denitrification is the process by which nitrate is reduced to nitrogen gas (N<sub>2</sub> or N<sub>2</sub>O) during organic matter decay in oxygen minima zones in the water column. The denitrification process enriches the nitrate pool with <sup>15</sup>N, which is incorporated in the particulate organic matter. Denitrification is governed by the surface water productivity related to SoAM strength and the water column ventilation. We analyzed the nitrogen isotopic ratio of sedimentary organic matter (SOM, δ<sup>15</sup>N<sub>SOM</sub>) to examine the denitrification in the eastern Arabian Sea. Total nitrogen (TN %) and total organic carbon (TOC%) are used to estimate the surface water productivity from the sediment collected during expedition IODP 355, Hole U1456A. We find that the δ<sup>15</sup>N<sub>SOM</sub> values vary between 7-9 ‰ during 3.22-3.15 Ma and 2.9-2.75 Ma indicating high denitrification. High δ<sup>15</sup>N<sub>SOM</sub> values coincide with high productivity as shown by both TN and TOC. It shows two major periods in the late Pliocene (3.22-3.15 Ma and 2.92-2.75 Ma) associated with stronger denitrification and high productivity. These results indicate the intensification of SoAM during warmer periods of Late Pliocene and at the start of intensification of Northern hemisphere glaciation. The enhanced denitrification during this period could possibly be due to a reduction in deep water ventilation and monsoon driven upsurge in productivity.</p>

Surface water productivity and sediment transport by Bering Strait throughflow in the Chukchi Shelf (the western Arctic Ocean) during the Holocene

The Holocene ◽  
2017 ◽  
Vol 28 (5) ◽  
pp. 814-826 ◽  
Author(s):  
Boo-Keun Khim ◽  
Mi Jung Lee ◽  
Hyen Goo Cho ◽  
Kwangkyu Park
Keyword(s):  
Surface Water ◽  
Sediment Transport ◽  
Sea Level ◽  
Water Productivity ◽  
Sediment Cores ◽  
Bering Strait ◽  
Biogenic Opal ◽  
The Holocene ◽  
Bering Strait Throughflow ◽  
Chukchi Shelf

Diverse paleoceanographic proxies from three sediment cores (GC12ex, JPC35, and JPC30) collected from the Chukchi Shelf north of the Bering Strait elucidate the Holocene paleoceanographic changes (surface water productivity and sediment transport) caused by the Bering Strait throughflow from the Bering Sea into the Chukchi Sea. Lithology of three sediment cores identified the same three units. Based on comparison and correlation to adjacent age-dated cores as well as AMS 14C dates of core GC12ex, the boundary between Unit 1 and Unit 2a is dated about 8500 cal. yr BP, and the boundary between Unit 2a and Unit 2b is also dated about 4500 cal. yr BP. Consistent down-core profiles of the geochemical and isotopic properties among the three cores differentiate the paleoceanographic conditions corresponding to lithologic units. Based on the biogenic opal, total organic carbon, and δ13C values, Unit 1 is characterized by low surface water marine productivity under relatively shallow water with weak transport of Bering Strait throughflow. Unit 2a shows a mixture of terrestrial and marine contributions, indicating the onset of increased marine surface water productivity after the main flooding (~11,500 cal. yr BP) of the Bering Strait by the Holocene sea-level rise. Unit 2b exhibits stable and enhanced marine biogenic opal production similar to the present-day oceanographic conditions. Such paleoceanographic changes were confirmed by the clay minerals (smectite, illite, kaolinite, and chlorite) and detrital isotopes (εNd and 87Sr/86Sr). Thus, the Bering Strait throughflow played an important role on surface water productivity and sediment deposition in the Chukchi Shelf in response to Holocene sea-level rise after the opening of the Bering Strait.

scholarly journals Climate variability and ocean fertility during the Aptian Stage

2015 ◽  
Vol 11 (3) ◽  
pp. 383-402 ◽  
Author(s):  
C. Bottini ◽  
E. Erba ◽  
D. Tiraboschi ◽  
H. C. Jenkyns ◽  
S. Schouten ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Climatic Conditions ◽  
Low Fertility ◽  
Ontong Java Plateau ◽  
Direct Role ◽  
High Productivity ◽  
Oceanic Anoxic Event ◽  
Continental Runoff ◽  
Maximum Warming

Abstract. Several studies have been conducted to reconstruct temperature variations across the Aptian Stage, particularly during early Aptian Oceanic Anoxic Event (OAE) 1a. There is a general consensus that a major warming characterized OAE 1a, although some studies have provided evidence for transient "cold snaps" or cooler intervals during the event. The climatic conditions for the middle–late Aptian are less constrained, and a complete record through the Aptian is not available. Here we present a reconstruction of surface-water palaeotemperature and fertility based on calcareous nannofossil records from the Cismon and Piobbico cores (Tethys) and DSDP Site 463 (Pacific Ocean). The data, integrated with oxygen-isotope and TEX86 records, provide a detailed picture of climatic and ocean fertility changes during the Aptian Stage, which are discussed in relation to the direct/indirect role of volcanism. Warm temperatures characterized the pre-OAE 1a interval, followed by a maximum warming (of ~ 1.5–2 °C) during the early phase of anoxia under intense volcanic activity of the Ontong Java Plateau (OJP). A short-lived cooling episode interrupted the major warming, following a rapid increase in weathering rates. Nannofossils indicate that mesotrophic conditions were reached when temperatures were at their highest and OJP volcanism most intense, thus suggesting that continental runoff, together with increased input of hydrothermal metals, increased nutrient supply to the oceans. The latter part of OAE 1a was characterized by cooling events, probably promoted by CO2 sequestration during burial of organic matter. In this phase, high productivity was probably maintained by N2-fixing cyanobacteria, while nannofossil taxa indicating higher fertility were rare. The end of anoxia coincided with the cessation of volcanism and a pronounced cooling. The mid-Aptian was characterized by highest surface-water fertility and progressively decreasing temperatures, probably resulting from intense continental weathering drawing down pCO2. The lowest temperatures, combined with low fertility, were reached in the middle–late Aptian across the interval characterized by blooming of Nannoconus truittii. The prolonged cooling was followed by significant warming across the Aptian–Albian boundary. The data presented suggest that OJP activity played a direct role in inducing global warming during the early Aptian, whereas other mechanisms (weathering, deposition of organic matter) acted as feedback processes, favouring temporary cooler interludes.

A mesocosm study using four native Hawaiian plants to assess nitrogen accumulation under varying surface water nitrogen concentrations

2010 ◽  
Vol 62 (10) ◽  
pp. 2389-2397
Author(s):  
C. U. Unser ◽  
G. L. Bruland ◽  
A. Hood ◽  
K. Duin
Keyword(s):  
Surface Water ◽  
Aboveground Biomass ◽  
Plant Biomass ◽  
Native Hawaiian ◽  
The Other ◽  
Nitrogen Accumulation ◽  
Biomass Growth ◽  
Accumulation Rates ◽  
Nitrogen Concentrations ◽  
Growth Differences

Accumulation of nitrogen (N) by native Hawaiian riparian plants from surface water was measured under a controlled experimental mesocosm setting. Four species, Cladium jamaicense, Cyperus javanicus, Cyperus laevigatus, and Cyperus polystachyos were tested for their ability to survive in coconut fiber coir log media with exposure to differing N concentrations. It was hypothesized that the selected species would have significantly different tissue total nitrogen (TN) concentrations, aboveground biomass, and TN accumulation rates because of habitat preference and physiological growth differences. A general linear model (GLM) analysis of variance (ANOVA) determined that species differences accounted for the greatest proportion of variance in tissue TN concentration, aboveground biomass growth, and accumulation rates, when compared with the other main effects (i.e. N concentration, time) and their interactions. A post hoc test of means demonstrated that C. jamaicense had significantly higher tissue TN concentration, aboveground biomass growth, and accumulation rates than the other species under all N concentrations. It was also hypothesized that tissue TN concentrations and biomass growth would increase in plants exposed to elevated N concentrations, however data did not support this hypothesis. Nitrogen accumulation rates by species were controlled by differences in plant biomass growth.

Distribution of soluble heavy metals between ionic and complexed forms in a saturated sediment as affected by pH and redox conditions

1998 ◽  
Vol 37 (6-7) ◽  
pp. 165-171 ◽  
Author(s):  
W. H. Patrick ◽  
M. Verloo
Keyword(s):  
Organic Matter ◽  
Metal Complexes ◽  
Cation Exchange ◽  
Size Distribution ◽  
Size Range ◽  
The Other ◽  
Redox Conditions ◽  
Soluble Organic Matter ◽  
Other Hand ◽  
Reducing Conditions

Research was undertaken to determine the effects of pH and redox potential on heavy metal speciation and on the size distribution of the organo-metal complexes in the soluble fraction of sediment-water systems. A cation exchange technique was effective in separating free and complexed metal ions. Fe, Mn and Zn differed in the extent of complexation with soluble organic matter. Under reducing conditions approximately two thirds of the soluble Fe was in a complexed form that was not sorbed in passing through the cation exchange resin. Soluble Mn on the other hand, was almost completely ionic under reducing conditions, with only a trace amount passing through the resin column. Over 90 percent of the soluble Zn was complexed under reduced conditions, with only 9 percent sorbed onto the resin. The complexed Fe and Zn were bound to soluble organic matter particles with equivalent molecular weight greater than 25,000 while Mn passed through this size filter. There were marked differences in the size distribution of the various organo-metal complexes under different redox and pH conditions. The soluble Fe was associated with both the largest and smallest size ranges of soluble organic matter. The effect of pH was most evident in the smallest size range with much more complexed iron being present at low pHs. Mn, on the other hand, was associated with only the smallest size range under all pH and redox conditions, reflecting its ionic nature. The greater solubility and mobility of Mn probably accounts for it being depleted relative to iron in Gulf Coast sediments. Hg and Pb were associated with only the largest size soluble complexes and were little affected by pH and redox conditions.

Cenomanian–Turonian drowning of the Arabian Carbonate Platform, the İnişdere section, Adıyaman, SE Turkey

2019 ◽  
Vol 498 (1) ◽  
pp. 189-210 ◽  
Author(s):  
O. Mulayim ◽  
O. I. Yilmaz ◽  
B. Sarı ◽  
K. Tasli ◽  
M. Wagreich
Keyword(s):  
Sea Level ◽  
Carbonate Platform ◽  
Accumulation Rates ◽  
Sea Level Changes ◽  
Carbonate Production ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Se Turkey ◽  
Arabian Platform

AbstractThe Cenomanian–Turonian carbonate ramp in the Adıyaman Region of SE Turkey (Northern Arabian Platform) records an abrupt shift from benthic carbonate deposits to pelagic deposits near the Cenomanian–Turonian boundary event (CTBE) in the İnişdere stratigraphic section and surrounding borehole sections. A positive δ13C excursion of up to 2.15% is recorded in carbonate and organic carbon deposited around the CTBE and provides evidence of a direct link between the CTBE and oceanic anoxic events and the demise of the shallow carbonate production in the Derdere Formation. The microfacies analyses, biostratigraphic dating and palaeoenvironmental interpretations suggest that the platform was drowned near the CTBE as a result of changing environmental conditions. The microfacies indicating significant deepening show a contemporaneity to equivalent surfaces globally and thus strongly support an isochronous formation of Cenomanian–Turonian facies by eustatic sea-level changes. Anoxia spreading over the platform drastically reduced the carbonate production as observed in the studied sections and, therefore, resulted in a reduction in carbonate accumulation rates. Regional/local subsidence and a coeval sea-level rise during the late Cenomanian to early Turonian interval were the cause of the drowning of the platform, including regional anoxia at the northern Arabian platform linked to the Cenomanian–Turonian oceanic anoxic event (OAE2).

scholarly journals Capacidad productiva de cruzas de variedades de polinización libre combinadas con híbridos simples de maíz.

2016 ◽  
Vol 8 (2) ◽  
pp. 139
Author(s):  
Alejandro Espinosa ◽  
Margarita Tadeo ◽  
Angel Piña ◽  
Rafael Martínez
Keyword(s):  
Sea Level ◽  
Seed Production ◽  
The Other ◽  
Potential Productivity ◽  
Productivity Level ◽  
High Productivity

Given the acceplance, in the high valleys of Mexico -2200 to 2600 mts. over sea level-, of free-pollination strains and the high productivity of hybrids, we considered the alternative of combining these frec-pollination strains with the H-34, thus obtaining another experi-mental single hybrid and our goal was to determine its potential productivity level. The strains known aas Ixtlahuaca, Santiago Yeche and Acambay improved from 37,3% to 20,8% their productivity when crossed with H-34, such was not the case with the strains Almoloya de Juarez and V-23. The other single hybrid was named 417, and it led to aHigher productivity in Ixtlahuaca with 29.1%. When we conbined H-33 x 417 it yielded 9728 kglha, a 7% higher than that of 9088kg/ha with H-33. The results of VS-22x 417 were very similartothose with VS-22. The results indicated that we could use H-34 and perhaps other single hybrids in combination with free-pollina-tion strains, thus obtaining a certain level of heterosis and facilitating seed production, but based on the different responses, this should beevaluated previous to any combination be performed.

scholarly journals Climate variability and relationship with ocean fertility during the Aptian Stage

2014 ◽  
Vol 10 (1) ◽  
pp. 689-738 ◽  
Author(s):  
C. Bottini ◽  
E. Erba ◽  
D. Tiraboschi ◽  
H. C. Jenkyns ◽  
S. Schouten ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
High Surface ◽  
Climatic Conditions ◽  
Low Fertility ◽  
High Fertility ◽  
Ontong Java Plateau ◽  
Direct Role ◽  
High Productivity ◽  
Oceanic Anoxic Event

Abstract. Several studies have been conducted to reconstruct temperature variations across the Aptian Stage, particularly during the Early Aptian Oceanic Anoxic Event (OAE)1a. There is a general consensus that a major warming characterized the OAE 1a, although some studies have provided evidence for transient "cold snaps" or cooler intervals during the event. The climatic conditions for the middle–late Aptian are less constrained, and a complete record through the Aptian is not available. Here we present a reconstruction of surface-water palaeotemperature and fertility based on calcareous nannofossil records from the Cismon and Piobbico cores (Tethys) and DSDP Site 463 (Pacific Ocean). The data, integrated with oxygen-isotope and TEX86 records, provide a detailed picture of climatic and ocean fertility changes during the Aptian Stage, which are discussed in relation to the direct/indirect role of volcanism. Warm temperatures characterized the pre-OAE 1a interval followed by a maximum warming (of ~2–3 °C) during the early phase of anoxia under intense volcanic activity of the Ontong Java Plateau (OJP). A short-lived (~35 ky) cooling episode interrupted the major warming, following a rapid increase of weathering rates. Nannofossils indicate that eutrophic conditions were reached when temperatures were at their highest and OJP volcanism most intense, thus suggesting that continental runoff, together with increased input of hydrothermal metals, increased nutrient supply to the oceans. The latter part of OAE 1a was characterized by cooling events, probably promoted by CO2 sequestration during burial of organic matter. In this phase, high productivity was probably maintained by N2-fixing cyanobacteria while nannofossil taxa indicating high fertility were rare. The end of anoxia coincided with the cessation of volcanism and a pronounced cooling. The mid-Aptian was characterized by high surface-water fertility and progressively decreasing temperatures, probably resulting from intense continental weathering drawing down pCO2. The lowest temperatures, combined with low fertility, were reached in the middle–late Aptian across the interval characterized by blooming of Nannoconus truittii. The data presented suggest that OJP activity played a direct role in inducing global warming during the early Aptian, whereas other mechanisms (weathering, deposition of organic matter) acted as feedback processes, favouring temporary cooler interludes.

Is volcanic ash responsible for the enrichment of organic carbon in shales? Quantitative characterization of organic-rich shale at the Ordovician-Silurian transition

2020 ◽  
Author(s):  
Ke Zhao ◽  
Xuebin Du ◽  
Yongchao Lu ◽  
Fang Hao ◽  
Zhanhong Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Primary Productivity ◽  
Volcanic Ash ◽  
Trace Element Analysis ◽  
Nutrient Content ◽  
Major Elements ◽  
Redox Conditions ◽  
Element Analysis ◽  
High Productivity

Subaerial volcanism and atmospheric volcanic ash deposition have been recognized as factors that can greatly affect the nutrient content of the surface ocean and the redox conditions of the water column. Black siliceous, organic-rich mudstone and shale containing numerous volcanic ash layers were deposited in the South China Block during the Ordovician-Silurian transition. Although this association has been observed in other regions, whether there is a relationship between volcanic ash and the organic carbon contents and the effect of volcanic ash remains unclear. Based on analysis of the concentrations of major elements, trace elements, and total organic carbon in the volcanic ash and shale, we found that anoxic and high-productivity environments existed during the Ordovician-Silurian transition and that organic matter was preferentially preserved under these conditions. For the volcanic ash, we quantitatively estimated the depletion of the nutrient elements Fe, Si, and P (in percentages). The calculated results show that leaching removed 25−75% of the Fe, Si, and P in most of the ash samples in the study area, potentially leading to high marine primary productivity in the surface water. Redox conditions also played a major role in the preservation of organic matter. The trace element analysis results show that although productivity was high during the Ordovician-Silurian transition, organic matter was preferentially preserved in the Lower Silurian strata. Therefore, high organic matter flux and good preservation conditions both contributed to the formation of the organic-rich shale, and volcanic ash was the dominant source of nutrients for primary productivity.

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