Interprétation séquentielle du Jurassique inférieur et moyen du Sud du Bassin Parisien a partir des corrélations diagraphiques calées sur le forage de Couy (Cher, France)

Lorenz, Jacqueline; Gély, Jean-Pierre

doi:10.1016/s0016-6995(94)80223-8

Cited by 4 publications

(4 citation statements)

References 11 publications

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“…Together with the presence of a clear ravinement in the sediments at 355.05 m, these data suggest that the uppermost Pliensbachian and PliensbachianToarcian (Pl-To) transition of the Sancerre-Couy core are characterized by an important hiatus. In contrast to the previous studies of Lorenz et al (1987), Gély and Lorenz (1991) and Lorenz and Gély (1994), the position of the PliensbachianToarcian boundary remains uncertain here within the unzoned interval at 355.80-352.80 m (Fig. 2).…”

Section: Toarciancontrasting

confidence: 95%

“…The ammonite biozonation of the whole Sancerre-Couy core was presented in various papers following the original description of the core (Degouy et al, 1986;Lorenz et al, 1987Lorenz et al, , 1988Lorenz et al, , 1991Gély and Lorenz, 1991;Lorenz and Gély, 1994). None of these papers provide a synthetic and comprehensive description of all ammonite specimens found with their precise depth.…”

Section: Revision Of the Ammonite Biozonation Of The Sancerre-couy Corementioning

confidence: 99%

“…The investigated Sancerre-Couy core spans the complete Lower Jurassic and has a reasonably well-established ammonite biozonation for the upper SinemurianPliensbachian (Degouy et al, 1986;Lorenz, 1987;Lorenz et al, 1988;Gély and Lorenz, 1991;Lorenz and Gély, 1994;Boulila et al, 2014). Situated in the Paris Basin, the studied core represents an area located between the NW European and SE and SW Mediterranean realms, hence allowing for comparison of the different established biostratigraphic schemes.…”

Section: Introductionmentioning

confidence: 99%

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Sinemurian–Pliensbachian calcareous nannofossil biostratigraphy and organic carbon isotope stratigraphy in the Paris Basin: Calibration to the ammonite biozonation of NW Europe

Peti¹,

Thibault²,

Clémence³

et al. 2017

Palaeogeography, Palaeoclimatology, Palaeoecology

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Abstract:The biostratigraphy of Sinemurian to lower Toarcian calcareous nannofossils has been investigated in the Sancerre-Couy core (Paris Basin), which contains a mixed assemblage of species with affinities to the northern and southern areas of the peritethyan realm, thus allowing for the use and calibration of the Mediterranean Province (Italy/S France) and NW Europe (UK) biozonation schemes. This study is based on semi-quantitative analyses of the calcareous nannofossil assemblage performed on 145 samples and the recorded bioevents are calibrated to the NW European Ammonite Zonation and to a new organic carbon isotope curve based on 385 data points. The main bioevents, i.e. the first occurrences of Parhabdolithus liasicus, Crepidolithus pliensbachensis, Crepidolithus crassus, Mitrolithus lenticularis, Similiscutum cruciulus sensu lato, Lotharingius hauffii, Crepidolithus cavus and Lotharingius sigillatus as well as the last occurrence of Parhabdolithus robustus, have been identified. However, we show that a large number of standard biostratigraphic markers show inconsistent occurrences at the base and top of their range, possibly accounting for some of the significant discrepancies observed between the different domains. In addition to the nine main bioevents used for the biozonation of the core, we document an additional 50 distinct bioevents, evaluate their reliability and discuss their potential significance by comparison to previous studies. A total of five significant negative organic carbon isotope excursions are identified and defined in the Paris Basin including the well-documented Sinemurian-Pliensbachian boundary event. One positive excursion is further defined in the Pliensbachian interval. Our calibration of high-resolution calcareous nannofossil biostratigraphy to ammonite biostratigraphy and organic carbon isotopes represents a new stratigraphic reference for the Lower Jurassic series.

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Section: Toarciancontrasting

confidence: 95%

Section: Revision Of the Ammonite Biozonation Of The Sancerre-couy Corementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sinemurian–Pliensbachian calcareous nannofossil biostratigraphy and organic carbon isotope stratigraphy in the Paris Basin: Calibration to the ammonite biozonation of NW Europe

Peti¹,

Thibault²,

Clémence³

et al. 2017

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…This prominent decrease in kaolinite abundance has also to be discussed in terms of sea level change. Based on the well-establish long-term sequence stratigraphy for European basins (de Graciansky et al, 1998;Hallam, 2001) and inferred relative sea level curve proposed for the Jurassic of the Paris Basin (Guillocheau et al, 2000;Hermoso et al, 2013;Lorenz and Gély, 1994), the late Pliensbachian experienced an episode of sea level fall (Fig. 3).…”

Section: Long-term Climatic Trend During the End Of Pliensbachianmentioning

confidence: 99%

Continental weathering and climatic changes inferred from clay mineralogy and paired carbon isotopes across the early to middle Toarcian in the Paris Basin

Hermoso

Pellenard

2014

Palaeogeography, Palaeoclimatology, Palaeoecology

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Lower Toarcian strata (Lower Jurassic) have been extensively studied with a view to understanding the oceanographic, climatic and biological processes that drove the Earth's system into an Oceanic Anoxic Event (OAE). For this time period, the evolution of the European marine seaways is now relatively well constrained owing to multiple geochemical studies, but investigations regarding climatic trends in the continental realm remain sparse. In the present study, we test the clay mineralogy as a continental climate-sensitive proxy in the well-documented Sancerre core (southern Paris Basin). We compare variations in the kaolinite content with pCO 2 fluctuations (derived from paired carbon isotopes; Δ 13 C = δ 13 C carb δ 13 C org), taking advantage of the detailed chemostratigraphic, palaeoenvironmental and sequence stratigraphy frameworks established for this core material. The results indicate a substantial decrease in kaolinite abundance at the end of the Pliensbachian, which is compatible with a long-term diminution in continental weathering and an inferred temperature decrease. The early Toarcian, prior to the carbon cycle perturbation and deposition of black shale facies, remained relatively cold with minima in both the proportion of kaolinite and reconstructed pCO 2. The mineralogical and geochemical responses across the prominent negative carbon isotope excursion (CIE) itself are not univocal. The first of four steps that compose the negative limb of the CIE at Sancerre is associated with decreased kaolinite and pCO 2 , and increased carbonate oxygen isotope ratios. Taken together, these trends are compatible with a transient cooling phase immediately preceding the onset of black shale deposition. Conversely, the subsequent steps are marked by substantial enrichment in kaolinite that matches increased osmium isotope ratios measured in Yorkshire, providing compelling evidence for rapid increases in continental weathering and riverine runoff forced by intensification of greenhouse conditions during the CIE. Relaxation in the intensity of continental weathering, as suggested by resumed low kaolinite abundance is seen immediately after the cessation of CO 2 input (after the fourth step of the CIE). The interval spanning the upper portion of the early Toarcian and the middle Toarcian records a subsequent long-term increase in the proportion of kaolinite synchronous with significant clay enrichment of the sediment. Continued greenhouse conditions, even after the recovery from the carbon isotope perturbation and "regional" black shale deposition, are likely related to sustained CO 2 emission by Karoo-Ferrar volcanism through the considered interval.

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Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations

Ruhl

Hesselbo

Hinnov

et al. 2016

Earth and Planetary Science Letters

127

114

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Interprétation séquentielle du Jurassique inférieur et moyen du Sud du Bassin Parisien a partir des corrélations diagraphiques calées sur le forage de Couy (Cher, France)

Cited by 4 publications

References 11 publications

Sinemurian–Pliensbachian calcareous nannofossil biostratigraphy and organic carbon isotope stratigraphy in the Paris Basin: Calibration to the ammonite biozonation of NW Europe

Sinemurian–Pliensbachian calcareous nannofossil biostratigraphy and organic carbon isotope stratigraphy in the Paris Basin: Calibration to the ammonite biozonation of NW Europe

Continental weathering and climatic changes inferred from clay mineralogy and paired carbon isotopes across the early to middle Toarcian in the Paris Basin

Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations

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