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Karl B. Föllmi - One of the best experts on this subject based on the ideXlab platform.
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A global palaeoclimatic reconstruction for the Valanginian based on clay mineralogical and geochemical data
Earth-Science Reviews, 2020Co-Authors: Guillaume Charbonnier, Jorge Spangenberg, Thierry Adatte, Jeanfrancois Deconinck, Stéphanie Duchamp-alphonse, Christophe Colin, Karl B. FöllmiAbstract:High-resolution clay mineral and δ18Ocarb analyses have been performed on three sections of Valanginian age (Early Cretaceous), from northwestern (~20–30°N) and southern (~53°S) Tethyan realms. The data have been integrated in a large set of published mineralogical (clays), and geochemical (δ18Ocarb, δ18Obivalve, δ18Olenticulina, δ18Obelemnite, and TEX86) data from 17 sections, situated between ~45°N and ~53°S. Based on this data set, we provide new insights into Valanginian climate conditions from a wide range of palaeolatitudes. We highlight climate trends within specific areas and identify main climate belts. In the Proto-North Atlantic realm (~15–17°N) large amounts of smectite together with the occurrence of palygorskite testify for a semi-arid climate belt throughout the Valanginian. Significant variations in kaolinite content in the northwestern Tethyan realm (~20 to 30°N) suggest that this realm has been more sensitive to changes in hydrological cycling and subsequent erosion and runoff processes during the early to early–late Valanginian transition interval. This time interval, that is coincident with the pronounced positive and globally recognized carbon isotope excursion (CIE; the Weissert episode), documents the wet conditions of a humid subtropical climate belt. Temperature ranges derived from δ18O records suggest climate warming by about 3–5±0.9°C in the northern hemisphere, during the Weissert episode. This is followed by a global cooling of about ca. 1–5±0.9°C in both hemispheres, during the late Valanginian. We postulate that these patterns were due to interplays between tectonic and orbital factors, which have controlled the distribution of regional palaeoclimate belts during the Valanginian. The semi-arid belt expressed in the Proto North Atlantic realm has probably been induced by its specific palaeogeographic configuration and the existence of isolated basins, which were each characterized by strong and continuous thermohaline circulation. An eccentricity paced monsoon-like system might have played a significant role in maintaining the subtropical belt around the northwestern Tethyan realm, up to the mid latitudes (~35–45°N). Superimposed on these regional processes, a widespread magmatic pulse in Paraná-Etendeka volcanic activity might have stimulated greenhouse conditions, impacting marine biota and favouring the development of a dense vegetation cover on the continent. An increase in sedimentary burial of 13C depleted organic carbon on the continents may have contributed to the progressive global positive carbon isotope excursion. In the medium term, it has also probably led to a significant decrease in atmospheric CO2, as testified by the global cooling recorded during the late Valanginian in both hemispheres and the probable concomitant extension of polar ice caps.
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New stratigraphic data for the Lower Cretaceous Tirgan Formation, Kopet-Dagh Basin, NE Iran
Arabian Journal of Geosciences, 2019Co-Authors: Masoumeh Gheiasvand, Jorge Spangenberg, Annie Arnaud-vanneau, Abbas Ghaderi, Karl B. Föllmi, Thierry Adatte, Ali Reza AshouriAbstract:In this contribution, we describe a section through the Lower Cretaceous shallow-water platform sediments (Tirgan Formation) from the Kopet-Dagh basin (northern Tethys), which is located near Tirgan village, NE Iran. We used benthic foraminifera and planktonic organisms for biostratigraphy associated to the carbon isotope chemostratigraphy to constrain the age of the succession. Microfossils are grouped around the Feurtillia gracilis range zone (Upper Valanginian), the Campanellula capuensis range zone (Upper Hauterivian - Barremian), the Orbitolinid assemblage zone (Lower to Upper Aptian) and the Planktonic assemblage zone (Upper Aptian) as well as several genera and species are reported from the Kopet-Dagh for the first time (e.g., C. capuensis , Colomiella sp., Cuneolina composaurii , F. gracilis ). The new biostratigraphic data allow us to date the lower part of the section as Berriasian (?), Valanginian, and Hauterivian, which is older than the age range previously assumed for the Tirgan Fm. (Barremian-Aptian). Our age determinations are consistent with those obtained by the carbonate carbon isotope chemostratigraphy and the resulting age model allows to assign a Berriasian (?)-Valanginian to Albian age to the Tirgan Fm. Furthermore, a prominent positive excursion near the base of the section can be correlated with the Weissert Episode, and likely also the Faraoni Episode is registered in this succession. The Tirgan Fm. displays an explicit onlap pattern to the west, which explains the diachrony in ages of the base of the formation. This suggests the effect of a long-term subsidence in the Kopet-Dagh during the Early Cretaceous, following the Cimmerian phase of orogenesis.
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mercury enrichment indicates volcanic triggering of Valanginian environmental change
Scientific Reports, 2017Co-Authors: Guillaume Charbonnier, Thierry Adatte, Chloe Morales, S. Westermann, Stephanie Duchampalphonse, Karl B. FöllmiAbstract:The Valanginian stage (Early Cretaceous) includes an episode of significant environmental changes, which are well defined by a positive δ13C excursion. This globally recorded excursion indicates important perturbations in the carbon cycle, which has tentatively been associated with a pulse in volcanic activity and the formation of the Parana-Etendeka large igneous province (LIP). Uncertainties in existing age models preclude, however, its positive identification as a trigger of Valanginian environmental changes. Here we report that in Valanginian sediments recovered from a drill core in Wąwal (Polish Basin, Poland), and from outcrops in the Breggia Gorge (Lombardian Basin, southern Switzerland), and Orpierre and Angles (Vocontian Basin, SE France), intervals at or near the onset of the positive δ13C excursion are significantly enriched in mercury (Hg). The persistence of the Hg anomaly in Hg/TOC, Hg/phyllosilicate, and Hg/Fe ratios shows that organic-matter scavenging and/or adsorbtion onto clay minerals or hydrous iron oxides only played a limited role. Volcanic outgassing was most probably the primary source of the Hg enrichments, which demonstrate that an important magmatic pulse triggered the Valanginian environmental perturbations.
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Mercury enrichment indicates volcanic triggering of the Valanginian Environmental Change
Scientific Reports, 2017Co-Authors: Guillaume Charbonnier, Thierry Adatte, C. Morales, S. Duchamp-alphonse, S. Westermann, Karl B. FöllmiAbstract:The Valanginian stage (Early Cretaceous) includes an episode of significant environmental changes, which are well defined by a positive δ13C excursion. This globally recorded excursion indicates important perturbations in the carbon cycle, which has tentatively been associated with a pulse in volcanic activity and the formation of the Paraná-Etendeka large igneous province (LIP). Uncertainties in existing age models preclude, however, its positive identification as a trigger of Valanginian environmental changes. Here we report that in Valanginian sediments recovered from a drill core in Wąwał (Polish Basin, Poland), and from outcrops in the Breggia Gorge (Lombardian Basin, southern Switzerland), and Orpierre and Angles (Vocontian Basin, SE France), intervals at or near the onset of the positive δ13C excursion are significantly enriched in mercury (Hg). The persistence of the Hg anomaly in Hg/TOC, Hg/phyllosilicate, and Hg/Fe ratios shows that organic-matter scavenging and/or adsorbtion onto clay minerals or hydrous iron oxides only played a limited role. Volcanic outgassing was most probably the primary source of the Hg enrichments, which demonstrate that an important magmatic pulse triggered the Valanginian environmental perturbations.
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evolution of the northern tethyan helvetic platform during the late berriasian and early Valanginian
The Depositional Record, 2016Co-Authors: Chloe Morales, Thierry Adatte, Jorge E Spangenberg, Annie Arnaudvanneau, Karl B. FöllmiAbstract:The Early Cretaceous period is characterized by widespread carbonate production in tropical and subtropical epicontinental seas, which was modulated by changes in sea-level, detrital and nutrient fluxes, and the global carbon cycle. As a result, carbonate platforms were sensitive recorders of environmental change, which often anticipated global environmental perturbations. A good example is provided by the northern Tethyan carbonate platform, which is presently preserved in the central European Helvetic Alps. There, the latest early to late Valanginian Weissert episode of global change, which is defined by the first important positive shift in δ13C records of the Cretaceous, is expressed by a prolonged, stepwise drowning phase. In this contribution, a detailed reconstruction of palaeoenvironmental change before and during the Weissert episode is provided based on three representative sections of the Helvetic platform. The sections are placed along a deepening transect and correlated by means of ammonite and microfossil biostratigraphy, sequence stratigraphy and δ13C chemostratigraphy. In a first phase of palaeoenvironmental change during the latest Berriasian, photozoan carbonate production was stopped by a major and hitherto undetected drowning episode, which was followed by a phase of renewed carbonate production by heterozoan biota. This phase was linked to major sea-level rise, a change to a more humid climate and strong regional subsidence associated with tectonic block tilting. During the Valanginian, the circulation of nutrient-enriched sea waters prevented a return to oligotrophic conditions and two further drowning episodes occurred, which are both documented by condensed phosphate-rich beds and dated as middle early Valanginian and late Valanginian to early Hauterivian. The exact causes of the three-step deterioration in carbonate production are not established but a link to episodic volcanic activity is likely, eventually related to the formation of the Parana-Etendeka large igneous province.
Thierry Adatte - One of the best experts on this subject based on the ideXlab platform.
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A global palaeoclimatic reconstruction for the Valanginian based on clay mineralogical and geochemical data
Earth-Science Reviews, 2020Co-Authors: Guillaume Charbonnier, Jorge Spangenberg, Thierry Adatte, Jeanfrancois Deconinck, Stéphanie Duchamp-alphonse, Christophe Colin, Karl B. FöllmiAbstract:High-resolution clay mineral and δ18Ocarb analyses have been performed on three sections of Valanginian age (Early Cretaceous), from northwestern (~20–30°N) and southern (~53°S) Tethyan realms. The data have been integrated in a large set of published mineralogical (clays), and geochemical (δ18Ocarb, δ18Obivalve, δ18Olenticulina, δ18Obelemnite, and TEX86) data from 17 sections, situated between ~45°N and ~53°S. Based on this data set, we provide new insights into Valanginian climate conditions from a wide range of palaeolatitudes. We highlight climate trends within specific areas and identify main climate belts. In the Proto-North Atlantic realm (~15–17°N) large amounts of smectite together with the occurrence of palygorskite testify for a semi-arid climate belt throughout the Valanginian. Significant variations in kaolinite content in the northwestern Tethyan realm (~20 to 30°N) suggest that this realm has been more sensitive to changes in hydrological cycling and subsequent erosion and runoff processes during the early to early–late Valanginian transition interval. This time interval, that is coincident with the pronounced positive and globally recognized carbon isotope excursion (CIE; the Weissert episode), documents the wet conditions of a humid subtropical climate belt. Temperature ranges derived from δ18O records suggest climate warming by about 3–5±0.9°C in the northern hemisphere, during the Weissert episode. This is followed by a global cooling of about ca. 1–5±0.9°C in both hemispheres, during the late Valanginian. We postulate that these patterns were due to interplays between tectonic and orbital factors, which have controlled the distribution of regional palaeoclimate belts during the Valanginian. The semi-arid belt expressed in the Proto North Atlantic realm has probably been induced by its specific palaeogeographic configuration and the existence of isolated basins, which were each characterized by strong and continuous thermohaline circulation. An eccentricity paced monsoon-like system might have played a significant role in maintaining the subtropical belt around the northwestern Tethyan realm, up to the mid latitudes (~35–45°N). Superimposed on these regional processes, a widespread magmatic pulse in Paraná-Etendeka volcanic activity might have stimulated greenhouse conditions, impacting marine biota and favouring the development of a dense vegetation cover on the continent. An increase in sedimentary burial of 13C depleted organic carbon on the continents may have contributed to the progressive global positive carbon isotope excursion. In the medium term, it has also probably led to a significant decrease in atmospheric CO2, as testified by the global cooling recorded during the late Valanginian in both hemispheres and the probable concomitant extension of polar ice caps.
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New stratigraphic data for the Lower Cretaceous Tirgan Formation, Kopet-Dagh Basin, NE Iran
Arabian Journal of Geosciences, 2019Co-Authors: Masoumeh Gheiasvand, Jorge Spangenberg, Annie Arnaud-vanneau, Abbas Ghaderi, Karl B. Föllmi, Thierry Adatte, Ali Reza AshouriAbstract:In this contribution, we describe a section through the Lower Cretaceous shallow-water platform sediments (Tirgan Formation) from the Kopet-Dagh basin (northern Tethys), which is located near Tirgan village, NE Iran. We used benthic foraminifera and planktonic organisms for biostratigraphy associated to the carbon isotope chemostratigraphy to constrain the age of the succession. Microfossils are grouped around the Feurtillia gracilis range zone (Upper Valanginian), the Campanellula capuensis range zone (Upper Hauterivian - Barremian), the Orbitolinid assemblage zone (Lower to Upper Aptian) and the Planktonic assemblage zone (Upper Aptian) as well as several genera and species are reported from the Kopet-Dagh for the first time (e.g., C. capuensis , Colomiella sp., Cuneolina composaurii , F. gracilis ). The new biostratigraphic data allow us to date the lower part of the section as Berriasian (?), Valanginian, and Hauterivian, which is older than the age range previously assumed for the Tirgan Fm. (Barremian-Aptian). Our age determinations are consistent with those obtained by the carbonate carbon isotope chemostratigraphy and the resulting age model allows to assign a Berriasian (?)-Valanginian to Albian age to the Tirgan Fm. Furthermore, a prominent positive excursion near the base of the section can be correlated with the Weissert Episode, and likely also the Faraoni Episode is registered in this succession. The Tirgan Fm. displays an explicit onlap pattern to the west, which explains the diachrony in ages of the base of the formation. This suggests the effect of a long-term subsidence in the Kopet-Dagh during the Early Cretaceous, following the Cimmerian phase of orogenesis.
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mercury enrichment indicates volcanic triggering of Valanginian environmental change
Scientific Reports, 2017Co-Authors: Guillaume Charbonnier, Thierry Adatte, Chloe Morales, S. Westermann, Stephanie Duchampalphonse, Karl B. FöllmiAbstract:The Valanginian stage (Early Cretaceous) includes an episode of significant environmental changes, which are well defined by a positive δ13C excursion. This globally recorded excursion indicates important perturbations in the carbon cycle, which has tentatively been associated with a pulse in volcanic activity and the formation of the Parana-Etendeka large igneous province (LIP). Uncertainties in existing age models preclude, however, its positive identification as a trigger of Valanginian environmental changes. Here we report that in Valanginian sediments recovered from a drill core in Wąwal (Polish Basin, Poland), and from outcrops in the Breggia Gorge (Lombardian Basin, southern Switzerland), and Orpierre and Angles (Vocontian Basin, SE France), intervals at or near the onset of the positive δ13C excursion are significantly enriched in mercury (Hg). The persistence of the Hg anomaly in Hg/TOC, Hg/phyllosilicate, and Hg/Fe ratios shows that organic-matter scavenging and/or adsorbtion onto clay minerals or hydrous iron oxides only played a limited role. Volcanic outgassing was most probably the primary source of the Hg enrichments, which demonstrate that an important magmatic pulse triggered the Valanginian environmental perturbations.
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Mercury enrichment indicates volcanic triggering of the Valanginian Environmental Change
Scientific Reports, 2017Co-Authors: Guillaume Charbonnier, Thierry Adatte, C. Morales, S. Duchamp-alphonse, S. Westermann, Karl B. FöllmiAbstract:The Valanginian stage (Early Cretaceous) includes an episode of significant environmental changes, which are well defined by a positive δ13C excursion. This globally recorded excursion indicates important perturbations in the carbon cycle, which has tentatively been associated with a pulse in volcanic activity and the formation of the Paraná-Etendeka large igneous province (LIP). Uncertainties in existing age models preclude, however, its positive identification as a trigger of Valanginian environmental changes. Here we report that in Valanginian sediments recovered from a drill core in Wąwał (Polish Basin, Poland), and from outcrops in the Breggia Gorge (Lombardian Basin, southern Switzerland), and Orpierre and Angles (Vocontian Basin, SE France), intervals at or near the onset of the positive δ13C excursion are significantly enriched in mercury (Hg). The persistence of the Hg anomaly in Hg/TOC, Hg/phyllosilicate, and Hg/Fe ratios shows that organic-matter scavenging and/or adsorbtion onto clay minerals or hydrous iron oxides only played a limited role. Volcanic outgassing was most probably the primary source of the Hg enrichments, which demonstrate that an important magmatic pulse triggered the Valanginian environmental perturbations.
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evolution of the northern tethyan helvetic platform during the late berriasian and early Valanginian
The Depositional Record, 2016Co-Authors: Chloe Morales, Thierry Adatte, Jorge E Spangenberg, Annie Arnaudvanneau, Karl B. FöllmiAbstract:The Early Cretaceous period is characterized by widespread carbonate production in tropical and subtropical epicontinental seas, which was modulated by changes in sea-level, detrital and nutrient fluxes, and the global carbon cycle. As a result, carbonate platforms were sensitive recorders of environmental change, which often anticipated global environmental perturbations. A good example is provided by the northern Tethyan carbonate platform, which is presently preserved in the central European Helvetic Alps. There, the latest early to late Valanginian Weissert episode of global change, which is defined by the first important positive shift in δ13C records of the Cretaceous, is expressed by a prolonged, stepwise drowning phase. In this contribution, a detailed reconstruction of palaeoenvironmental change before and during the Weissert episode is provided based on three representative sections of the Helvetic platform. The sections are placed along a deepening transect and correlated by means of ammonite and microfossil biostratigraphy, sequence stratigraphy and δ13C chemostratigraphy. In a first phase of palaeoenvironmental change during the latest Berriasian, photozoan carbonate production was stopped by a major and hitherto undetected drowning episode, which was followed by a phase of renewed carbonate production by heterozoan biota. This phase was linked to major sea-level rise, a change to a more humid climate and strong regional subsidence associated with tectonic block tilting. During the Valanginian, the circulation of nutrient-enriched sea waters prevented a return to oligotrophic conditions and two further drowning episodes occurred, which are both documented by condensed phosphate-rich beds and dated as middle early Valanginian and late Valanginian to early Hauterivian. The exact causes of the three-step deterioration in carbonate production are not established but a link to episodic volcanic activity is likely, eventually related to the formation of the Parana-Etendeka large igneous province.
Bernard Pittet - One of the best experts on this subject based on the ideXlab platform.
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Community replacement of neritic carbonate organisms during the late Valanginian platform demise: a new record from the Provence Platform.
Palaeogeography Palaeoclimatology Palaeoecology, 2012Co-Authors: Aurélie Bonin, Annie Arnaud-vanneau, Thierry Adatte, Bernard Pittet, Emmanuelle Vennin, Emmanuelle Pucéat, Michel Guiraud, Emanuela MattioliAbstract:The Valanginian is marked by amajor platform demise inducing a hiatus in the northern Tethyan neritic carbonate record from the top of the lower Valanginian to the lower Hauterivian. New biostratigraphic and chemostratigraphic data from the Ollioules section (Provence Platform, southern France) are presented here, demonstrating that a large part of the upper Valanginian is preserved in an inner platform environment. The thick, upper Valanginian, aggrading carbonate succession is observed in an aborted rift domain, implying relatively low subsidence. In this context, a relatively long-term sea-level rise was required to sustain a keep-up style of carbonate production. Like the Apulian Platform, the remarkable preservation of the Provence Platform may have been favored by its remoteness from terrigenous source areas, as suggested by the low clastic inputs and low P-accumulation rates. Two main biotic community replacements are observed in Ollioules. The first saw the development of abundantmicrobialites and algae at the onset of the late Valanginian. A Tubiphytes concentration occurred during the coolest climatic conditions and the transition towards arid conditions, whereas the subsequent Lithocodium-Bacinella and orbitolinids assemblages developed under low nutrient conditions during a warmer interval. Both assemblages may have been triggered by increased alkalinity. The second community replacement saw the installation of coral- and rudist-dominated communities during the latest Valanginian to early Hauterivian. They indicate a change to oligotrophic, open marine conditions. Six medium-scale sequences have been defined in Ollioules, indicating short-term transgressive-regressive trends superimposed on a long-term transgression. Low nutrient inputs and relatively low subsidence in an aggradational contextmay explain the survival of the isolated Provence Carbonate Platform during a time of widespread drowning episodes and platform demise in the northern Tethyan domain.
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Evidence for a complex Valanginian nannoconid decline in the Vocontian basin (South East France).
Marine Micropaleontology, 2012Co-Authors: Nicolas Barbarin, Benjamin Gréselle, Bernard Pittet, Aurélie Bonin, Emmanuelle Vennin, Emmanuelle Pucéat, Emanuela Mattioli, Henri Cappetta, Michael M. JoachimskiAbstract:The Early Cretaceous is punctuated by widespread biocalcification crises. These are characterized by decrease in the carbonate platform growth and, in the pelagic realm, by a decline in Nannoconus relative abundance in the calcareous nannofossil assemblages. The Valanginian Nannoconus decline started before the positive δ13C excursion characterizing the Weissert Event. The nannoconid decline is investigated in two sections of the Vocontian Basin, La Charce and Vergol, which are biostratigraphically well-constrained and contain wellpreserved calcareous nannofossils. Absolute and relative abundances of Nannoconus show a polyphased decline, with a first decrease in the interval from the Campylotoxus to the Verrucosum Ammonite Subzones before the positive δ13C shift, and a second decrease from the end of the Peregrinus to the base of the Radiatus Ammonite Zones concomitant with the long-term decrease in δ13C. These two declines are separated by an important increase in the Nannoconus abundance from the Verrucosum to the Peregrinus Ammonite Subzones concomitant with a slight short-term decrease of δ13C. Biometric analysis shows size changes of N. steinmannii and N. kamptneri along the nannoconid decline. The patterns of abundances and size changes seem to be related to paleoenvironmental changes, mainly characterized by a temperature decrease and variable nutrient supply. The described Valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the Vocontian basin as well as in the Atlantic and Tethys Oceans. These spatial correlations suggest a supra-regional character for the Valanginian nannoconid recovery event best recorded in the Vocontian Basin and at low latitudes.
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Sea-level reconstructions from the Peri-Vocontian Zone (South-east France) point to Valanginian glacio-eustasy
Sedimentology, 2010Co-Authors: Benjamin Gréselle, Bernard PittetAbstract:The Valanginian is a period of global environmental change as illustrated by sedimentary, palaeontological, geochemical and climatic perturbations. A production crisis in most of the carbonate platforms suggests important changes in palaeoenvironmental conditions. During the same time interval, a major positive excursion in delta 13C, the Weissert Event, suggests perturbations of the carbon cycle from the latest Early Valanginian to the Early Hauterivian. In order to better understand the link between these changes, sea-level fluctuations have been reconstructed in detail from the Middle Berriasian to the earliest Hauterivian. Sections from the Peri-Vocontian Zone (South-east France) have been investigated because of the good quality of outcrops on the carbonate platforms, their margins and in the Vocontian Basin. Sections ranging from the most proximal zone (Swiss Jura) to the basin were interpreted in terms of sequence stratigraphy and cyclostratigraphy, and correlated at high resolutions. Using the identified small, medium and large-scale sequences as well as depositional geometries, sea-level fluctuations were reconstructed. Two main trends are evidenced during the studied interval: (i) the peak amplitude (magnitude) of the sea-level fluctuations increased gradually from the Middle Berriasian to the Early Valanginian, and reached a maximum (more than 50 m) from the middle Early Valanginian to the Valanginian/Hauterivian boundary; and (ii) sea-level variations were quite symmetrical during the Late Berriasian, slightly asymmetrical during the Early Valanginian and strongly asymmetrical (fast sea-level rise, slow fall) from the latest Early Valanginian to the earliest Hauterivian. Moreover, three orders of sea-level fluctuations were recognized in the sedimentary rocks of the Peri-Vocontian Zone. Platform-basin correlations and cyclostratigraphic interpretations of the basinal sections evidence an astronomical control on the sea-level variations, mainly by the two eccentricity cycles of 100 and 400 kyr. The increase in the amplitude of the sea-level fluctuations and their change from symmetrical to asymmetrical can be related to the onset of a major cooling event in the Early Valanginian. Fast transgressions followed by slower regressions would correspond to waxing and waning of high-latitudinal ice during most of the Valanginian, especially from the latest Early Valanginian to the latest Late Valanginian. Glacio-eustatic sea-level fluctuations in tune with the 100 and 400 kyr eccentricity cycles are in agreement with glaciations during the Valanginian
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sea level reconstructions from the peri vocontian zone south east france point to Valanginian glacio eustasy
Sedimentology, 2010Co-Authors: Benjamin Gréselle, Bernard PittetAbstract:The Valanginian is a period of global environmental change as illustrated by sedimentary, palaeontological, geochemical and climatic perturbations. A production crisis in most of the carbonate platforms suggests important changes in palaeoenvironmental conditions. During the same time interval, a major positive excursion in δ13C, the Weissert Event, suggests perturbations of the carbon cycle from the latest Early Valanginian to the Early Hauterivian. In order to better understand the link between these changes, sea-level fluctuations have been reconstructed in detail from the Middle Berriasian to the earliest Hauterivian. Sections from the Peri-Vocontian Zone (South-east France) have been investigated because of the good quality of outcrops on the carbonate platforms, their margins and in the Vocontian Basin. Sections ranging from the most proximal zone (Swiss Jura) to the basin were interpreted in terms of sequence stratigraphy and cyclostratigraphy, and correlated at high resolutions. Using the identified small, medium and large-scale sequences as well as depositional geometries, sea-level fluctuations were reconstructed. Two main trends are evidenced during the studied interval: (i) the peak amplitude (magnitude) of the sea-level fluctuations increased gradually from the Middle Berriasian to the Early Valanginian, and reached a maximum (more than 50 m) from the middle Early Valanginian to the Valanginian/Hauterivian boundary; and (ii) sea-level variations were quite symmetrical during the Late Berriasian, slightly asymmetrical during the Early Valanginian and strongly asymmetrical (fast sea-level rise, slow fall) from the latest Early Valanginian to the earliest Hauterivian. Moreover, three orders of sea-level fluctuations were recognized in the sedimentary rocks of the Peri-Vocontian Zone. Platform-basin correlations and cyclostratigraphic interpretations of the basinal sections evidence an astronomical control on the sea-level variations, mainly by the two eccentricity cycles of 100 and 400 kyr. The increase in the amplitude of the sea-level fluctuations and their change from symmetrical to asymmetrical can be related to the onset of a major cooling event in the Early Valanginian. Fast transgressions followed by slower regressions would correspond to waxing and waning of high-latitudinal ice during most of the Valanginian, especially from the latest Early Valanginian to the latest Late Valanginian. Glacio-eustatic sea-level fluctuations in tune with the 100 and 400 kyr eccentricity cycles are in agreement with glaciations during the Valanginian.
Benjamin Gréselle - One of the best experts on this subject based on the ideXlab platform.
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no evidence for anoxia during the Valanginian carbon isotope event an organic geochemical study from the vocontian basin se france
Global and Planetary Change, 2012Co-Authors: Ariane Kujau, Benjamin Gréselle, Ulrich Heimhofer, Christian Ostertaghenning, Jorg MutterloseAbstract:Abstract The Valanginian time interval (Early Cretaceous) is characterized by a positive carbon isotope excursion (CIE) which represents the first of several prominent Cretaceous δ 13 C anomalies. A combined chemostratigraphic and organic-geochemical approach has been chosen to investigate the composition and distribution of sedimentary organic matter (OM) deposited before the Valanginian CIE, during its onset and plateau-phase. This was done to test whether this CIE is accompanied by changes in marine primary production and/or OM preservation. Biostratigraphically well-calibrated deposits from two hemipelagic sections located in the Vocontian Basin of SE France are used as sedimentary archives. A newly established high-resolution δ 13 C record covering the composite succession shows a characteristic Valanginian pattern and enables a detailed correlation with existing carbon isotope curves from the northern Tethyan margin. The analyzed solvent extractable fraction of the sedimentary OM is mainly composed of a marine origin with an admixture of land plant material. Variations in specific biomarkers for cyanobacteria (2α-methyl-hopanes), dinoflagellates (dinosterane or 4-desmethyl-23,24-dimethyl steranes) and terrigenous plant-derived OM (odd‐numbered long-chain n -alkanes) as well as the sterane/hopane ratio, the C 35 hopane index and the isoprenoids pristane and phytane were investigated. In contrast to the well-studied mid-Cretaceous Oceanic Anoxic Events (OAEs), neither significant OM enrichment nor prominent fluctuations in the selected biomarker abundances can be observed during the build-up phase of the Valanginian CIE. This points to relatively stable marine paleoenvironmental conditions with well-oxygenated bottom waters. Prior to the CIE, four cm-thick, finely laminated, dark layers (known as Barrande layers) with total organic carbon content reaching up to 4% show an exception from the generally stable biomarker pattern. Sedimentological and biomarker evidence support deposition under less oxygenated conditions for the Barrande layers. However, their occurrence clearly predates the onset of the positive δ 13 C carb shift (by about 180 kyrs). Contrary to the subsequent mid-Cretaceous CIEs, the occurrence of widespread anoxia associated with the Valanginian CIE cannot be confirmed for the Vocontian Basin.
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Evidence for a complex Valanginian nannoconid decline in the Vocontian basin (South East France).
Marine Micropaleontology, 2012Co-Authors: Nicolas Barbarin, Benjamin Gréselle, Bernard Pittet, Aurélie Bonin, Emmanuelle Vennin, Emmanuelle Pucéat, Emanuela Mattioli, Henri Cappetta, Michael M. JoachimskiAbstract:The Early Cretaceous is punctuated by widespread biocalcification crises. These are characterized by decrease in the carbonate platform growth and, in the pelagic realm, by a decline in Nannoconus relative abundance in the calcareous nannofossil assemblages. The Valanginian Nannoconus decline started before the positive δ13C excursion characterizing the Weissert Event. The nannoconid decline is investigated in two sections of the Vocontian Basin, La Charce and Vergol, which are biostratigraphically well-constrained and contain wellpreserved calcareous nannofossils. Absolute and relative abundances of Nannoconus show a polyphased decline, with a first decrease in the interval from the Campylotoxus to the Verrucosum Ammonite Subzones before the positive δ13C shift, and a second decrease from the end of the Peregrinus to the base of the Radiatus Ammonite Zones concomitant with the long-term decrease in δ13C. These two declines are separated by an important increase in the Nannoconus abundance from the Verrucosum to the Peregrinus Ammonite Subzones concomitant with a slight short-term decrease of δ13C. Biometric analysis shows size changes of N. steinmannii and N. kamptneri along the nannoconid decline. The patterns of abundances and size changes seem to be related to paleoenvironmental changes, mainly characterized by a temperature decrease and variable nutrient supply. The described Valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the Vocontian basin as well as in the Atlantic and Tethys Oceans. These spatial correlations suggest a supra-regional character for the Valanginian nannoconid recovery event best recorded in the Vocontian Basin and at low latitudes.
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Sea-level reconstructions from the Peri-Vocontian Zone (South-east France) point to Valanginian glacio-eustasy
Sedimentology, 2010Co-Authors: Benjamin Gréselle, Bernard PittetAbstract:The Valanginian is a period of global environmental change as illustrated by sedimentary, palaeontological, geochemical and climatic perturbations. A production crisis in most of the carbonate platforms suggests important changes in palaeoenvironmental conditions. During the same time interval, a major positive excursion in delta 13C, the Weissert Event, suggests perturbations of the carbon cycle from the latest Early Valanginian to the Early Hauterivian. In order to better understand the link between these changes, sea-level fluctuations have been reconstructed in detail from the Middle Berriasian to the earliest Hauterivian. Sections from the Peri-Vocontian Zone (South-east France) have been investigated because of the good quality of outcrops on the carbonate platforms, their margins and in the Vocontian Basin. Sections ranging from the most proximal zone (Swiss Jura) to the basin were interpreted in terms of sequence stratigraphy and cyclostratigraphy, and correlated at high resolutions. Using the identified small, medium and large-scale sequences as well as depositional geometries, sea-level fluctuations were reconstructed. Two main trends are evidenced during the studied interval: (i) the peak amplitude (magnitude) of the sea-level fluctuations increased gradually from the Middle Berriasian to the Early Valanginian, and reached a maximum (more than 50 m) from the middle Early Valanginian to the Valanginian/Hauterivian boundary; and (ii) sea-level variations were quite symmetrical during the Late Berriasian, slightly asymmetrical during the Early Valanginian and strongly asymmetrical (fast sea-level rise, slow fall) from the latest Early Valanginian to the earliest Hauterivian. Moreover, three orders of sea-level fluctuations were recognized in the sedimentary rocks of the Peri-Vocontian Zone. Platform-basin correlations and cyclostratigraphic interpretations of the basinal sections evidence an astronomical control on the sea-level variations, mainly by the two eccentricity cycles of 100 and 400 kyr. The increase in the amplitude of the sea-level fluctuations and their change from symmetrical to asymmetrical can be related to the onset of a major cooling event in the Early Valanginian. Fast transgressions followed by slower regressions would correspond to waxing and waning of high-latitudinal ice during most of the Valanginian, especially from the latest Early Valanginian to the latest Late Valanginian. Glacio-eustatic sea-level fluctuations in tune with the 100 and 400 kyr eccentricity cycles are in agreement with glaciations during the Valanginian
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sea level reconstructions from the peri vocontian zone south east france point to Valanginian glacio eustasy
Sedimentology, 2010Co-Authors: Benjamin Gréselle, Bernard PittetAbstract:The Valanginian is a period of global environmental change as illustrated by sedimentary, palaeontological, geochemical and climatic perturbations. A production crisis in most of the carbonate platforms suggests important changes in palaeoenvironmental conditions. During the same time interval, a major positive excursion in δ13C, the Weissert Event, suggests perturbations of the carbon cycle from the latest Early Valanginian to the Early Hauterivian. In order to better understand the link between these changes, sea-level fluctuations have been reconstructed in detail from the Middle Berriasian to the earliest Hauterivian. Sections from the Peri-Vocontian Zone (South-east France) have been investigated because of the good quality of outcrops on the carbonate platforms, their margins and in the Vocontian Basin. Sections ranging from the most proximal zone (Swiss Jura) to the basin were interpreted in terms of sequence stratigraphy and cyclostratigraphy, and correlated at high resolutions. Using the identified small, medium and large-scale sequences as well as depositional geometries, sea-level fluctuations were reconstructed. Two main trends are evidenced during the studied interval: (i) the peak amplitude (magnitude) of the sea-level fluctuations increased gradually from the Middle Berriasian to the Early Valanginian, and reached a maximum (more than 50 m) from the middle Early Valanginian to the Valanginian/Hauterivian boundary; and (ii) sea-level variations were quite symmetrical during the Late Berriasian, slightly asymmetrical during the Early Valanginian and strongly asymmetrical (fast sea-level rise, slow fall) from the latest Early Valanginian to the earliest Hauterivian. Moreover, three orders of sea-level fluctuations were recognized in the sedimentary rocks of the Peri-Vocontian Zone. Platform-basin correlations and cyclostratigraphic interpretations of the basinal sections evidence an astronomical control on the sea-level variations, mainly by the two eccentricity cycles of 100 and 400 kyr. The increase in the amplitude of the sea-level fluctuations and their change from symmetrical to asymmetrical can be related to the onset of a major cooling event in the Early Valanginian. Fast transgressions followed by slower regressions would correspond to waxing and waning of high-latitudinal ice during most of the Valanginian, especially from the latest Early Valanginian to the latest Late Valanginian. Glacio-eustatic sea-level fluctuations in tune with the 100 and 400 kyr eccentricity cycles are in agreement with glaciations during the Valanginian.
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impact des variations paléoclimatiques sur la sédimentation carbonatée au Valanginien
2007Co-Authors: Benjamin GréselleAbstract:L'étude des géométries et des faciès des dépôts sédimentaires du Berriasien-Valanginien de la Plate-forme du Jura-Dauphiné jusqu'au Bassin Vocontien (SE France) met en évidence la crise globale des plates-formes carbonatées au Valanginien, celle-ci se faisant en plusieurs étapes. Le développement de glaces en hautes latitudes entraîne des variations du niveau marin de plusieurs dizaines de mètres. L'asymétrie de ces variations traduit des débâcles rapides et des englacements plus lents qui sont contrôlés par les cycles d'excentricité de l'orbite terrestre. Le refroidissement global couplé à une hausse des apports en nutriments sous un climat plus humide et la baisse du niveau marin global vont progressivement diminuer la production des plates-formes, installer des systèmes de rampe, jusqu'à la mort de ces systèmes au Valanginien supérieur. La comparaison de cet évènement de crise avec celui de l'Aptien-Albien suggère qu'à plus d'une reprise le Mésozoïque a connu des épisodes glaciaires.
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multi proxy record of orbital scale changes in climate and sedimentation during the weissert event in the Valanginian bersek marl formation gerecse mts hungary
Cretaceous Research, 2017Co-Authors: József Pálfy, Gregory D Price, Mathieu Martinez, David Bajnai, Anita Nyerges, Istvan FőzyAbstract:Abstract The Valanginian positive carbon isotope excursion and associated environmental changes, known as the Weissert Event, is the first in the series of Cretaceous Earth system perturbations. Here, we develop a multiproxy cyclostratigraphy from a 31.2-m-thick Upper Valanginian to lowermost Hauterivian section of the Bersek Marl Formation in Gerecse Mountains, Hungary, comprising alternating marlstone layers of varying clay and carbonate content. The bulk carbonate δ13C signal shows sustained, elevated values (up to 2.7‰) up to 19.2 m, followed by a decreasing trend upsection. Together with biostratigraphic data, this suggests that the lower part of the section was deposited during the plateau phase of the Late Valanginian Weissert Event. Spectral analyses of the multiproxy dataset, including magnetic susceptibility measurements and gamma-ray spectroscopy on the lower part of the section, led to the identification of precession, obliquity, and long and short eccentricity signals. A mean sedimentation rate of 14 m/Myr was calculated based on astronomical tuning. The cyclicity in the proxy signals reflects dilution cycles induced by the fluctuating rate of detrital runoff into the basin. This supports the idea that orbitally-forced humid-arid cycles controlled the pelagic alternating sedimentation during the Early Cretaceous throughout the Tethyan area.
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astrochronology of the Valanginian hauterivian stages early cretaceous chronological relationships between the parana etendeka large igneous province and the weissert and the faraoni events
Global and Planetary Change, 2015Co-Authors: Stéphane Reboulet, Mathieu Martinez, Jeanfrancois Deconinck, Pierre Pellenard, Laurent Riquier, Mathieu MoiroudAbstract:The Geological Time Scale shows large uncertainties on durations and ages of Berriasian to Albian stages (Early Cretaceous), which impact climate and paleoceanographic reconstructions. Here, we provide a new astrochronology of the Hauterivian Stage anchored on (1) recent biostratigraphically well-constrained published radio-isotopic dates, and (2) a previously published astrochronology of the Valanginian Stage. A new duration of the Hauterivian Stage is assessed here at 5.93 ± 0.41 myr. The retained age model, anchored on a latest CA-ID-TIMS U–Pb age from a tuff level in the Hauterivian of the Neuquen Basin (Argentina), dates the base of the Valanginian Stage at − 137.05 ± 1.0 Ma, the base of the Hauterivian Stage at − 131.96 ± 1.0 Ma, and the top of the Hauterivian Stage at − 126.02 ± 1.0 Ma. In addition, the onset of the mid-Valanginian Weissert Event is dated at − 135.22 ± 1.0 Ma and the onset of the Faraoni Event at − 126.73 ± 1.0 Ma. The duration of the mid-Valanginian carbon-isotope excursion, associated to the Weissert Event, is assessed at 5.85 myr, with a rapid phase of increasing δ13C values (0.60 myr), a phase of stable δ13C values (1.48 myr), and smooth decrease in δ13C values (3.77 myr). The calibration provided here highlights that the onset of the activity of the Parana–Etendeka province and the start of the Weissert Event coincided, suggesting that the Parana–Etendeka province may have played a major role on the climatic and oceanographic changes during the mid-Valanginian.
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Astrochronology of the Valanginian-Hauterivian stages (Early Cretaceous): chronological relationships between the Paraná-Etendeka large igneous province and the Weissert and the Faraoni events.
Global and Planetary Change, 2015Co-Authors: Mathieu Martinez, Stéphane Reboulet, Jeanfrancois Deconinck, Pierre Pellenard, Laurent Riquier, Miguel Company, Mathieu MoiroudAbstract:The Geological Time Scale shows large uncertainties on durations and ages of Berriasian to Albian stages (Early Cretaceous), which impact climate and paleoceanographic reconstructions. Here, we provide a new astrochronology of the Hauterivian Stage anchored on (1) recent biostratigraphically well-constrained published radio-isotopic dates, and (2) a previously published astrochronology of the Valanginian Stage. A new duration of the Hauterivian Stage is assessed here at 5.93 ± 0.41 myr. The retained age model, anchored on a latest CA-ID-TIMS U–Pb age from a tuff level in the Hauterivian of the Neuquén Basin (Argentina), dates the base of the Valanginian Stage at − 137.05 ± 1.0 Ma, the base of the Hauterivian Stage at − 131.96 ± 1.0 Ma, and the top of the Hauterivian Stage at − 126.02 ± 1.0 Ma. In addition, the onset of the mid-Valanginian Weissert Event is dated at − 135.22 ± 1.0 Ma and the onset of the Faraoni Event at − 126.73 ± 1.0 Ma. The duration of the mid-Valanginian carbon-isotope excursion, associated to the Weissert Event, is assessed at 5.85 myr, with a rapid phase of increasing δ13C values (0.60 myr), a phase of stable δ13C values (1.48 myr), and smooth decrease in δ13C values (3.77 myr). The calibration provided here highlights that the onset of the activity of the Paraná–Etendeka province and the start of the Weissert Event coincided, suggesting that the Paraná–Etendeka province may have played a major role on the climatic and oceanographic changes during the mid-Valanginian.
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Astrochronology of the Valanginian stage from GSSP candidates and hypostratotype.
2013Co-Authors: Mathieu Martinez, Stéphane Reboulet, Jeanfrancois Deconinck, Pierre Pellenard, Laurent RiquierAbstract:The Valanginian Stage currently displays no radiometric age, which severely hampers palaeoceanographic reconstructions for this time interval. An astrochronology of the Valanginian Stage using the stable 405-kyr eccentricity cycle was performed on biostratigraphically well-calibrated standard sections from the Vocontian Basin (southeastern France). High-resolution gamma-ray spectrometry signals were obtained from orbitally driven marl-limestone alternations from five sections in the basin, and they display the same long-term trends. The spectral analyses present the pervasive record of the 405-kyr eccentricity cycle together with precession, obliquity, and 2.4-Myr eccentricity. Based on the identification of the 405-kyr eccentricity cycle, the duration of the Valanginian Stage is assessed at 5.08 Myr. Since the Weissert Event appears to be ~3 Myr older than the onset of the Paraná-Etendeka Large Igneous Province activity, a link between these events is unlikely. We therefore propose, following Gröcke et al. (2005) and Westermann et al. (2010), that continental organic carbon storage and carbonate platform demise are responsible for the onset of the δ13C positive excursion. In addition, a stronger obliquity control appears in the O. (O.) nicklesi and C. furcillata subzones. This may be linked to the limited production of polar ice suggested for this time interval.
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Calibration astronomique du Valanginien et de l'Hauterivien (crétacé inférieur) : Implications paléoclimatiques et paléocéanographiques
2013Co-Authors: Mathieu MartinezAbstract:Une calibration orbitale du Valanginien et d’une partie de l’Hauterivien (Crétacé inférieur) est présentée au cours de ce travail. Celles-ci sont basées sur l’identification des cycles de l’excentricité à partir d’analyses spectrales menées sur des proxies climatiques mesurés à haute résolution sur des alternances marne/calcaire hémipélagiques.Cinq coupes de référence sont analysées dans le Bassin Vocontien (Sud-Est de la France), couvrant l’ensemble de l’étage du Valanginien. Une durée de 5,08 Ma est proposée pour cet étage à partir de l’identification du cycle de l’excentricité de 405 ka. Le cadre temporel proposé, combiné aux âges radioisotopiques disponibles, montre que la perturbation en 13C du Valanginien moyen (événement Weissert) est antérieure à la mise en place des trapps du Paraná-Etendeka. La forte expression de l’obliquité dans la partie supérieure du Valanginien pourrait refléter la mise en place de calottes polaires de faible extension.La transition Hauterivien-Barrémien de Río Argos (Sud-Est de l’Espagne) est traitée par une analyse multi-proxies (cortèges argileux et susceptibilité magnétique ou SM). Par comparaison avec les bancs calcaires, les interbancs marneux sont enrichis en kaolinite et en illite, appauvries en smectite et possèdent de fortes valeurs de SM. Cela reflète des conditions tropicales humides lors du dépôt des marnes tandis que les calcaires se déposent en climat semi-aride. Les durées des zones d’ammonite à P. ohmi et à T. hugii sont respectivement estimées à 0,78 Ma et 0,54 Ma. L’événement anoxique Faraoni a une durée comprise entre 100 et 150 ka. Par corrélation avec d’autres coupes, Río Argos apparaît être le meilleur candidat GSSP
