In the Paris Basin, marine deposits of the Vesles and Montagne de Laon Groups bracket terrestrial to littoral litho-units of the Mont Bernon Group. Since 2007, we study those Sparnacian facies, as they record the effects of a climate crisis linked to a massive release of greenhouse gases into the atmosphere. This hyperthermal event, the Paleocene Eocene Thermal Maximum (PETM), occurred 55.8 Ma ago, was brief (170 ka) and intense (+ 5 to 8°C vs. baseline). Studied as an analogue to the current global warming, it is marked by a negative isotopic excursion of 2 to 6 ‰ of the δ13C and coincides with environmental perturbations. About thirty reference successions have been studied, to which well-described information is incorporated, providing a comprehensive and detailed set of geological data. The aim is to 1) revise the lithostratigraphic nomenclature by integrating new δ13Corg and biostratigraphic data, 2) establish well-calibrated correlations in these series prone to hiatuses and lateral facies changes, 3) build a robust framework to reconstitute and discuss the evolution of landscapes, flora and fauna. We show a prominent record of the PETM over 15-25 m, marked by a strong increase in the sedimentation rate. Steps identified in the δ13Corg curves enable fine correlation, 1) especially at the beginning of the event in fluvial and more rarely lagoonal to lacustrine environments, 2) then in alluvial plains, with development of calcretes and variegated paleosols, 3) and in swamps, lakes and lagoons, formed in a context of rising waterlevel. We further observe faunal and floral turnovers, eutrophication of aquatic environments, extreme acme of Apectodinium and few other dinoflagellate cyst groups as well as the occurrence of new dinoflagellate species. Lateral facies variations are anchored and paleogeographic maps drawn. It appears that some lithounits previously considered as unique in the Paris Basin (e.g. lignite, plastic clay, fluvial sand, lacustrine limestone and lagoonal sediments) are not synchronous and cannot be regarded as stratigraphic markers for a unique event. This work has been funded by the Regolith and RGF programs of the BRGM, the French Research and Higher Education Ministry and the Belgian AFICI 08-1911 and BR/121/A3/PALEURAFRICA projects.
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RBINS Staff Publications 2019
Obtaining temperature data from the mid-Piacenzian warm period (mPWP) is a key factor in understanding the coming changes brought upon by anthropogenic climate change. The mPWP, a high-CO2 world with a paleogeography similar to modern times, has been used to validate and improve model retrodictions, which in turn enables assessing the prediction strength of these models1. For the first time, stable isotope analysis has been applied to the extinct tellinid bivalve Angulus benedeni benedeni, originating from the mid-Piacenzian of the Lillo Formation of Belgium in the southern North Sea basin. Multi-annual oxygen isotope records with a seasonal resolution obtained from its shell indicate that this species could live for up to a decade and formed monthly growth increments. From this oxygen isotope record, a clumped-isotope-based mean annual temperature of 12.6 ± 3.6°C was reconstructed. This is 2.1°C warmer than today2,3, 2.6°C warmer than the pre-industrial North Sea2, and in line with global Pliocene temperature estimates of +2-4°C compared to the pre-industrial climate4,5. The pristine nature of the aragonitic shell material was verified through electron backscatter diffraction analysis (EBSD), and backed up by light microscopy, X-ray diffraction, and X-ray fluorescence. The various microstructures as obtained from the EBSD maps have been described, and they provide a template of pristine A. benedeni benedeni material to which potentially altered shells may be compared. The bivalve A. benedeni benedeni is suitable for high resolution isotope-based paleoclimatic reconstruction and it can be used to unravel the marine conditions in the Pliocene North Sea basin at a seasonal scale, yielding enhanced insight into imminent western European climate conditions.1Dowsett, H. J. et al. Assessing confidence in Pliocene sea surface temperatures to evaluate predictive models. Nature Climate Change 2, 365-371 (2012). https://doi.org/10.1038/NCLIMATE1455 2Emeis, K.-C. et al. The North Sea — A shelf sea in the Anthropocene. Journal of Marine Systems 141, 18-33 (2015). https://doi.org/10.1016/j.jmarsys.2014.03.012 3Locarnini, R. A. et al. World Ocean Atlas 2018, Volume 1: Temperature. NOAA Atlas NESDIS 81. A. Mishonov, Technical Editor. 52pp. (2019). https://www.ncei.noaa.gov/access/world-ocean-atlas-2018/ 4Dowsett, H. J. et al. Sea surface temperature of the mid-Piacenzian ocean: a data-model comparison. Scientific reports 3, 1-8 (2013). https://doi.org/10.1038/srep02013 5Haywood, A. M. et al. The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity. Clim. Past 16, 2095-2123 (2020). https://doi.org/10.5194/cp-16-2095-2020
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RBINS Staff Publications 2022
