T1. Geochronology
The basic aim of geochronology is to place significant events (geological, climatological and archaeological events) in the Earth’s history within a common and absolute temporal framework. The dating techniques are very varied and can be either relative or absolute. Absolute geochronology, which is principally based on the use of radioactive phenomena, is invaluable for anchoring relative chronologies within an absolute timescale. The principal methods that we are developing are isotopic and magnetic stratigraphy (relative methods), and methods based on the analysis of uranium and thorium series, C14 dating, potassium/argon chronometry, tritium/helium-3 chronometry, and luminescence techniques (absolute dating methods). These different relative and absolute methods can be used in the study of climate archives (ice cores, continental and marine sediments, etc.), which provide us with a better understanding of the mechanisms governing our climate and which allow us to study the different dynamics at work in the environment (erosion, particulate and dissolved transfer, soils, groundwater, etc.), as well as the dynamics of human settlement and associated cultural transitions.
T1.4 – Dating of groundwater
- evaluation of residence-, transit-, and renewal times [3H/3He, 4He, CFCs, SF6]; [14C].
Outils Analytiques (Thèmes associés) :
-Spectrométrie de masse par accélérateur (SMA) : mesure du 14C (T1.1, T1.2, T1.3, T1.4)
-Spectrométrie de masse K-Ar et 40Ar/39Ar (T1.1, T1.2, T1.3)
-Paléomagnétisme (T1.1, T1.3)
- MC-ICP-MS ou ICPMS appliquées aux séries de l’Uranium (T1.1, T1.2, T1.3)
- MC-ICPMS (Sr) (T1.2)
- ICPMS-HR appliquées aux séries de l’Uranium (T1.1, T1.2, T1.3)
- Thermochronologie basse température (T1.1)
- Thermoluminescence (TL) et luminescence stimulée optiquement (OSL) (T1.1, T1.2).
-Spectrométrie de masse : dO2/N2, d18Oatm, 40Ar/38Ar, 40Ar/36Ar; mesures d15N (T1.3).
-Mesure du Tritium et des isotopes de l’Hélium par spectrométrie de masse (T1.4)
- EA-IRMS (13C, 15N) (T1.2)
- MICADAS (T1.1, T1.2, T1.3, T1.4)
T1.3 Dating of climate archives
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Dating of ice cores, forcings and climate variations at orbital and millennial scales [Absolute dating through measurement of 40Ar/36Ar and38Ar/36Ar ratios;Orbital tuning through O2/N2and d18O of O2; Ice age vs gas age relative dating based on thed15N of N2 ]
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Dating of continental climate transitions and events, at various scales, based on speleothems: history, millennium, climate cycles [U/Th] [14C]
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The relationship between climate and volcanism [40Ar/39Ar and40Ar/38Ar/36Ar dating]; [d18O isotopic stratigraphy]
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Changes in ocean circulation : the relationship between climate and ocean circulation [14C]; [ d18O isotopic stratigraphy]; [Palaeomagnetism, Magnetostratigraphy]
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Dating of lacustrine and palustrine records: 14C for lacustrine records, ostracods and pollen for palustrine records, and marine mollusc shells, Gamma-Ray Spectrometric dating. [14C]; [Gamma-ray Spectrometer]
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Dating of loess sequences: Bulk 14C dating and 14C dating of specific molecules[14C]
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Chronology of sedimentary formations, establishment of marine and fluvial terraces, aridification and formation of dune fields, moraines, etc. 14C dating of macro-remains.[14C]
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Archaeometry[d13C,d15N],[87Sr/86Sr]
T1.2 - Archaeometry and archaeology
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Chronology of settlements, Evolution of societies [K-Ar and40Ar/39Ar dating] [14C], [U/Th], [TL-OSL] etc.
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Characterisation of diet [d13C,d18O,d15N]
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Characterisation of technological choices (organic temper in pottery, textile fibres, etc.) [d13C,d15N]