scholarly journals Variation of kerogen assemblages and δ13CKerogen in Lower Toarcian successions of the southern Tethyan margin

2019 ◽  
Author(s):  
Bruno Rodrigues ◽  
Ricardo Silva ◽  
João Graciano Mendonça Filho ◽  
Luís Vítor Duarte ◽  
Matías Reolid ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Betic Cordillera ◽  
Global Constraints ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Middle Atlas ◽  
Ocean Carbon ◽  
Northern Tethyan Margin ◽  
Lusitanian Basin

The early Toarcian Oceanic Anoxic Event (T-OAE) is associated with an “excess” of C12 in the atmospheric and ocean carbon reservoirs and widespread occurrence of organic-rich facies around the globe. The T-OAE is recorded as a pronounced negative carbon isotopic excursion (CIE) in carbonates, fossil wood, and kerogens at the base of the Serpentinum (=Falciferum=Levisoni) Chronozone, positioned within a broad δ13C positive trend initiated at the base of the Lower Toarcian. Contrasts in deposition and preservation of OM between the northern and southern Tethyan margins are observed during the T-OAE. Several sections of the northern Tethyan margin are enriched in OM, whereas in the southern Tethyan margin, organic-rich facies are spatially and temporally restricted and have lower TOC. This dichotomy reflects differentiated depositional and environmental conditions between the two margins, controlled by the interplay of local, regional, and global constraints (distinct palaeogeographical location, OM type and source, palaeoceanography, climate, tectonics, etc.). This study investigates the variation of kerogen assemblages and δ13CKerogen in the Upper Pliensbachian–Lower Toarcian interval along the southern Tethyan margin, i.e. Lusitanian Basin (Portugal), Betic Cordillera (Spain), and Middle Atlas (Morocco). The objective is to contribute to the understanding of the paleoenvironmental variables and dynamics that influenced deposition and preservation of OM during the Late Pliensbachian–Early Toarcian in the Tethyan region. Preliminary analysis revealed that Upper Pliensbachian–Lower Toarcian kerogen assemblages from the Betic Cordillera, Lusitanian, and Middle Atlas basins are dominated by terrestrial particles (phytoclasts and sporomorphs) and have relatively more positive δ13C values when compared with correlative North-European sections. In the Lusitanian Basin and Betic Cordillera, the T-OAE negative CIE is observed in the δ13CKerogen record and is accompanied by an increase in terrestrial palynomorphs, non-opaque phytoclasts (NOP), and cuticle fragments. These increases are in line with the posited intensification of continental weathering, acceleration of the hydrological cycle, and increased export of terrestrial OM into marine environments during the T-OAE.

scholarly journals Variation of kerogen assemblages and δ13CKerogen in Lower Toarcian successions of the southern Tethyan margin

2019 ◽  
Author(s):  
Bruno Rodrigues ◽  
Ricardo Silva ◽  
João Graciano Mendonça Filho ◽  
Luís Vítor Duarte ◽  
Matías Reolid ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Betic Cordillera ◽  
Global Constraints ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Middle Atlas ◽  
Ocean Carbon ◽  
Northern Tethyan Margin ◽  
Lusitanian Basin

The early Toarcian Oceanic Anoxic Event (T-OAE) is associated with an “excess” of C12 in the atmospheric and ocean carbon reservoirs and widespread occurrence of organic-rich facies around the globe. The T-OAE is recorded as a pronounced negative carbon isotopic excursion (CIE) in carbonates, fossil wood, and kerogens at the base of the Serpentinum (=Falciferum=Levisoni) Chronozone, positioned within a broad δ13C positive trend initiated at the base of the Lower Toarcian. Contrasts in deposition and preservation of OM between the northern and southern Tethyan margins are observed during the T-OAE. Several sections of the northern Tethyan margin are enriched in OM, whereas in the southern Tethyan margin, organic-rich facies are spatially and temporally restricted and have lower TOC. This dichotomy reflects differentiated depositional and environmental conditions between the two margins, controlled by the interplay of local, regional, and global constraints (distinct palaeogeographical location, OM type and source, palaeoceanography, climate, tectonics, etc.). This study investigates the variation of kerogen assemblages and δ13CKerogen in the Upper Pliensbachian–Lower Toarcian interval along the southern Tethyan margin, i.e. Lusitanian Basin (Portugal), Betic Cordillera (Spain), and Middle Atlas (Morocco). The objective is to contribute to the understanding of the paleoenvironmental variables and dynamics that influenced deposition and preservation of OM during the Late Pliensbachian–Early Toarcian in the Tethyan region. Preliminary analysis revealed that Upper Pliensbachian–Lower Toarcian kerogen assemblages from the Betic Cordillera, Lusitanian, and Middle Atlas basins are dominated by terrestrial particles (phytoclasts and sporomorphs) and have relatively more positive δ13C values when compared with correlative North-European sections. In the Lusitanian Basin and Betic Cordillera, the T-OAE negative CIE is observed in the δ13CKerogen record and is accompanied by an increase in terrestrial palynomorphs, non-opaque phytoclasts (NOP), and cuticle fragments. These increases are in line with the posited intensification of continental weathering, acceleration of the hydrological cycle, and increased export of terrestrial OM into marine environments during the T-OAE.

scholarly journals Variation of kerogen assemblages and δ13CKerogen in Lower Toarcian successions of the southern Tethyan margin

2019 ◽  
Author(s):  
Bruno Rodrigues ◽  
Ricardo Silva ◽  
João Graciano Mendonça Filho ◽  
Luís Vítor Duarte ◽  
Matías Reolid ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Betic Cordillera ◽  
Global Constraints ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Middle Atlas ◽  
Ocean Carbon ◽  
Northern Tethyan Margin ◽  
Lusitanian Basin

The early Toarcian Oceanic Anoxic Event (T-OAE) is associated with an “excess” of C12 in the atmospheric and ocean carbon reservoirs and widespread occurrence of organic-rich facies around the globe. The T-OAE is recorded as a pronounced negative carbon isotopic excursion (CIE) in carbonates, fossil wood, and kerogens at the base of the Serpentinum (=Falciferum=Levisoni) Chronozone, positioned within a broad δ13C positive trend initiated at the base of the Lower Toarcian. Contrasts in deposition and preservation of OM between the northern and southern Tethyan margins are observed during the T-OAE. Several sections of the northern Tethyan margin are enriched in OM, whereas in the southern Tethyan margin, organic-rich facies are spatially and temporally restricted and have lower TOC. This dichotomy reflects differentiated depositional and environmental conditions between the two margins, controlled by the interplay of local, regional, and global constraints (distinct palaeogeographical location, OM type and source, palaeoceanography, climate, tectonics, etc.). This study investigates the variation of kerogen assemblages and δ13CKerogen in the Upper Pliensbachian–Lower Toarcian interval along the southern Tethyan margin, i.e. Lusitanian Basin (Portugal), Betic Cordillera (Spain), and Middle Atlas (Morocco). The objective is to contribute to the understanding of the paleoenvironmental variables and dynamics that influenced deposition and preservation of OM during the Late Pliensbachian–Early Toarcian in the Tethyan region. Preliminary analysis revealed that Upper Pliensbachian–Lower Toarcian kerogen assemblages from the Betic Cordillera, Lusitanian, and Middle Atlas basins are dominated by terrestrial particles (phytoclasts and sporomorphs) and have relatively more positive δ13C values when compared with correlative North-European sections. In the Lusitanian Basin and Betic Cordillera, the T-OAE negative CIE is observed in the δ13CKerogen record and is accompanied by an increase in terrestrial palynomorphs, non-opaque phytoclasts (NOP), and cuticle fragments. These increases are in line with the posited intensification of continental weathering, acceleration of the hydrological cycle, and increased export of terrestrial OM into marine environments during the T-OAE.

Pacing of late Pliensbachian and early Toarcian carbon cycle perturbations and environmental change in the westernmost Tethys (La Cerradura section, Subbetic Zone of the Betic Cordillera, Spain)

2021 ◽  
pp. SP514-2021-27
Author(s):  
R. L. Silva ◽  
M. Ruhl ◽  
C. Barry ◽  
M. Reolid ◽  
W. Ruebsam
Keyword(s):  
Regional Climate ◽  
Geographical Area ◽  
Betic Cordillera ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Detailed Assessment ◽  
Isotope Stratigraphy ◽  
Supplementary Material ◽  
Tethys Ocean

AbstractThe detailed assessment of high-resolution elemental and isotopic geochemical datasets collected from the marl-limestone alternations cropping out at La Cerradura (Subbetic domain of the Betic Cordillera, Spain) and chrono- and chemostratigraphic correlation with the reference Mochras borehole (Cardigan Bay Basin, UK) unveiled valuable new insights to the understanding of late Pliensbachian-early Toarcian palaeoenvironmental dynamics at a key geographical area between the northern European seaway and the Tethys Ocean.This study shows that deposition in the study area took place under dominantly oxic water column conditions, indicated, for example, by the generalised lack of enrichment in organic matter and redox metals typically associated with anoxia and euxinia. Carbon isotope stratigraphy (δ13CTOC) allowed to recognise the spinatum (=emaciatum in the Submediterranean Province), Pliensbachian-Toarcian, and early Toarcian Oceanic Anoxic Event negative carbon isotopic excursions and the late Pliensbachian positive carbon isotopic excursion. It is here suggested that the observed periodic changes in lithology and sedimentary geochemistry occur at orbital frequencies (i.e., long and short eccentricity and, tentatively, precession), hinting at an astronomical control of the local-regional climate and environment during the Pliensbachian and Toarcian in the mid-low latitude South Iberian palaeomargin area.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5473754

Enhanced hydrological cycle during Oceanic Anoxic Event 2 at southern high latitudes: New insights from IODP Site U1516

2022 ◽  
pp. 103735
Author(s):  
Hongjin Chen ◽  
Zhaokai Xu ◽  
Germain Bayon ◽  
Dhongil Lim ◽  
Sietske J. Batenburg ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
High Latitudes ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event

scholarly journals A perturbed hydrological cycle during Oceanic Anoxic Event 2

Geology ◽  
2013 ◽  
Vol 42 (2) ◽  
pp. 123-126 ◽  
Author(s):  
N. A. G. M. van Helmond ◽  
A. Sluijs ◽  
G.-J. Reichart ◽  
J. S. Sinninghe Damste ◽  
C. P. Slomp ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event

The impact of the Pliensbachian-Toarcian crisis on belemnite diversity and size distribution

2020 ◽  
Author(s):  
Kenneth De Baets ◽  
Patrícia Rita ◽  
Luís Vítor Duarte ◽  
Pascal Neige ◽  
Laura Piñuela ◽  
...  
Keyword(s):  
High Resolution ◽  
Species Turnover ◽  
Adult Size ◽  
Oceanic Anoxic Event ◽  
Species Cluster ◽  
Anoxic Event ◽  
Major Bottleneck ◽  
Scaling Analyses ◽  
The Impact ◽  
Lusitanian Basin

<p>The Pliensbachian–Toarcian transition has been considered a major bottleneck in the early evolution of belemnites, probably related to major palaeoenvironmental and climatic changes during the Early Toarcian. Previous research has focused on the study of belemnites from higher, temperate latitudes, while high-resolution studies on diversity and size of subtropical belemnite assemblages in the northwest Tethys are comparatively rare. The lack of high-resolution (ammonoid subzone) abundance data on diversity and size distributions of belemnite assemblages does not allow separating changes during the Pliensbachian–Toarcian boundary event from those during the Toarcian anoxic event. Sample standardized diversity analyses on new data from Iberian sections suggest the Pliensbachian–Toarcian corresponds to a slight decrease in diversity and an adult size decrease within dominant species. Cluster and non-metric multidimensional scaling analyses, however, indicate that the largest changes in diversity and palaeogeographic distribution of belemnite assemblages occurred during the Toarcian oceanic anoxic event (TOAE) rather than the Pliensbachian–Toarcian boundary. In southern basins like the Lusitanian Basin and Riff Mountains, belemnites even disappear entirely during the TOAE. More generally, the TOAE corresponds with an increase in body size of belemnite assemblages driven by species turnover. The lack of widespread anoxia in southern basins of the northwest Tethys indicates that direct impact of warming or increased pCO2 triggered by volcanism as well as indirect effects on nutrient availability and productivity might have played an important role during both crises.</p>

scholarly journals Paleoceanographic changes at the northern Tethyan margin during the Cenomanian–Turonian Oceanic Anoxic Event (OAE-2)

2010 ◽  
Vol 77 (1-2) ◽  
pp. 25-45 ◽  
Author(s):  
Holger Gebhardt ◽  
Oliver Friedrich ◽  
Bettina Schenk ◽  
Lyndsey Fox ◽  
Malcolm Hart ◽  
...  
Keyword(s):  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Northern Tethyan Margin

scholarly journals Cuantificación e interpolación de tendencias locales de temperatura y precipitación en zonas alto andinas de Cundinamarca y Boyacá (Colombia)

2010 ◽  
Vol 11 (2) ◽  
pp. 173 ◽  
Author(s):  
Edwin Rojas ◽  
Blanca Arce ◽  
Andrés Peña ◽  
Francisco Boshell ◽  
Miguel Ayarza
Keyword(s):  
Production Systems ◽  
Hydrological Cycle ◽  
Kendall Test ◽  
Maximum Temperature ◽  
Positive Trend ◽  
Weighted Interpolation ◽  
Weather Patterns ◽  
Statistical Confidence ◽  
Temperature And Precipitation ◽  
Inverse Distance Weighted Interpolation

<p>El cambio en el patrón climático global no sólo afecta la temperatura, sino el ciclo hidrológico con mayores variaciones en los ambientales locales. Con el fin de cuantificar las tendencias de temperatura máxima, mínima y precipitación media, se realizó un análisis no-paramétrico de las series de tiempo de 31 estaciones meteorológicas ubicadas en zonas alto andinas de Cundinamarca y Boyacá, con registros de 1985 a 2008. Se calcularon las tendencias de cambio de las variables climáticas para cada una de las estaciones mediante el método de estimación de pendiente de Sen y se utilizó la prueba de Mann- Kendall para determinar el nivel de confianza de dichas tendencias. La temperatura máxima mostró tendencias positivas con niveles de confianza significativa (&gt;90%) en la mayoría de estaciones climáticas. Para la temperatura mínima, la tendencia positiva fue detectada en menor número de estaciones pero con mayores niveles de confianza estadística (12 estaciones superaron el 95%). La precipitación mostró tendencias significativas (&gt;90%) sólo en siete de las 31 estaciones analizadas (seis de ellas fueron positivas y una negativa). Se utilizó el método de interpolación de distancia inversa ponderada (IDW) para generar los mapas de la distribución espacial de las tendencias. Mediante validación cruzada se encontró que el IDW tiene un mejor ajuste para la precipitación que para la temperatura. Se concluye que el cambio climático tiene manifestaciones muy locales en términos del comportamiento de las temperaturas y la precipitación para la zona de estudio, lo que podría generar impactos específicos sobre los sistemas productivos de la región.</p><p> </p><p><strong>Quantization and interpolation of local trends in temperature and precipitation in the high Andean areas of Cundinamarca and Boyaca (Colombia)</strong></p><p>Change in global weather patterns affects not only temperature, but also the hydrological cycle with greater variations in local environments. In order to quantify trends in maximum temperature and minimum and average precipitation, we performed a nonparametric analysis of time series of 31 meteorological stations located in the high Andes of Cundinamarca and Boyaca, with records from 1985 to 2008. We calculated the changing trends of climatic variables for each of the stations with the Sen slope estimator and we used the Mann-Kendall test to determine the confidence level of such trends. The maximum temperature showed positive trends with significant confidence levels (&gt; 90%) in most seasons. For the lowest temperature, the positive trend was detected in fewer stations but with higher levels of statistical confidence (12 stations exceeded 95%). Rainfall showed significant trends (&gt; 90%) in only seven of the 31 stations analyzed (six of them were positive and one negative). We used the method of inverse distance weighted interpolation (IDW) to generate maps of the spatial distribution of the trends. Cross validation found that IDW has a better fit for precipitation than for temperature. We conclude that climate change manifests very local expressions in terms of the behavior of temperatures and precipitation for the study area, which could lead to specific impacts on production systems in the region.</p>

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