0000000000410137
AUTHOR
Stephen P. Hesselbo
Evolution climatique au Jurassique inférieur (Sinémurien supérieur) de la zone Nord-Ouest européenne, déduit de la minéralogie des argiles et des isotopes du carbone
International audience
Milankovitch forcing of Early Jurassic wildfires
The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. Presently, Earth’s climate is warming and the frequency of large wildfires appears to be increasing. Recent research has indicated that Quaternary deposits reveal that wildfires respond to orbital forcings; however, to date no study has been able to test whether wildfire activity corresponds to changes over Milankovitch timescales in the deep past. A high-resolution astrochronology ex…
The Global Boundary Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (Lower Jurassic), Wine Haven, Yorkshire, UK
14 pages; International audience; Following votes by the Pliensbachian Working Group, the Jurassic Subcommission and the International Commission on Stratigraphy, IUGS ratified the proposed Global Boundary Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (Lower Jurassic) at the base of bed 73b in the Wine Haven section, Robin Hood's Bay, Yorkshire Coast, UK. This level contains the characteristic ammonite association Bifericeras donovani Dommergues and Meister and Apoderoceras sp. Complementary data include: a) Strontium-isotope stratigraphy, based on analysis of belemnites which yield a calcite 87Sr/86Sr ratio for the boundary level of 0.707425 and data supportin…
Population response during an Oceanic Anoxic Event: The case of Posidonotis (Bivalvia) from the Lower Jurassic of the Neuquén Basin, Argentina
Benthonic marine species show a wide range of biological reactions to seawater chemical changes through time, from subtle adjustments to extinction. The Early Toarcian Oceanic Anoxic Event (T-OAE) was recently recognized in the Neuquén Basin, Argentina, confirming its global scope. The event was identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13Corg) in bulk rock and fossil wood in the upper Pliensbachian–lower Toarcian interval in the Arroyo Lapa section (Neuquén). Simultaneously with collection of lithological samples, a high-resolution biostratigraphical survey was carried out, and the…
Late Jurassic palaeoclimatic change from clay mineralogy and gamma-ray spectrometry of the Kimmeridge Clay, Dorset, UK
Abstract: The Late Jurassic was a time of increasing aridity in NW Europe. Here, a new clay mineral dataset is presented from a 600 m thick composite core through the Kimmeridge Clay Formation, southern England. Clay mineral assemblages comprise mainly illite and kaolinite, with minor randomly interstratified illite–smectite mixed-layer clays. SEM observations indicate that clay minerals are mainly detrital, except in silty strata of late Tithonian age, which contain abundant pore-filling kaolinite aggregates. Th/K ratios determined from gamma-ray spectrometry mirror palaeoclimatically significant variations in kaolinite/illite ratios, with notable exception where diagenetic kaolinite occur…
Evolution climatique au Jurassique inférieur (Sinémuriensupérieur) de la zone Nord-Ouest européenne, déduit de laminéralogie des argiles et des isotopes du carbone
National audience; L’étude des minéraux argileux et des isotopes stables (carbone) du Sinémuriensupérieur du bassin de Cardigan Bay (forage de Mochras, Pays de Galles) et du bassinde Paris (forage de Montcornet, France) permet de mettre en évidence les conditionsenvironnementales et climatiques dominantes à cette période. Dans les deux bassins,situés à des paléolatitudes proches (30 à 35°N), les assemblages de minéraux argileuxcomprennent des chlorites, des illites, des interstratifiés illite-smectite (IS R1), dessmectites et des kaolinites dans des proportions variables. L'influence de la diagenèsed’enfouissement et de l'authigénèse étant négligeable dans les deux forages, lesminéraux argi…
Late Jurassic palaeoclimatic change from clay mineralogy and gamma-ray spectrometry of the Kimmeridge Clay, Dorset, UK
The Late Jurassic was a time of increasing aridity in NW Europe. Here, a new clay mineral dataset is presented from a 600 m thick composite core through the Kimmeridge Clay Formation, southern England. Clay mineral assemblages comprise mainly illite and kaolinite, with minor randomly interstratified illite–smectite mixed-layer clays. SEM observations indicate that clay minerals are mainly detrital, except in silty strata of late Tithonian age, which contain abundant pore-filling kaolinite aggregates. Th/K ratios determined from gamma-ray spectrometry mirror palaeoclimatically significant variations in kaolinite/illite ratios, with notable exception where diagenetic kaolinite occurs. Compari…