An increasing number of scientists recognize the value of speleothems1 as often extremely well-preserved archives of information about past climate, vegetation, hydrology, sea level, nuclide migration, water-rock interaction, landscape evolution, tectonics and human action. Well-constrained data are required to document past changes, reconstruct past patterns and predict future responses of the Earth system at a wide range of spatial and temporal scales. Speleothems are particularly useful in this regard because they can be found in many locations of the globe, sampled at high-resolution and reliably dated using high-precision uranium-series techniques.



Speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave. Most speleothems are composed of calcite formed by slow degassing of CO2 from supersaturated groundwater, but aragonite and gypsum forms are also common, particularly near cave entrances where evaporative effects are important. A host of different speleothem types decorate the walls, ceilings and floors of caves, and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions (temperature, chemistry, light) in the air or water-filled void. Subaerial forms include the familiar stalagmites, stalactites, draperies, flowstones. Subaqueous forms include rimstone pools, “rafts,” mammillary calcite wall-coatings and “dog-tooth” spar. For an extensive review of the types of speleothem that have been observed, see Hill and Forti (1997).

Speleothems are used in a multitude of ways to explore past environmental conditions, perhaps the most fundamental of which is their very presence or absence. Deposition of speleothems relies on sufficient water supply and soil CO2 to enable dissolution and transport of reactants in the vadose zone to underlying caves. In arid or glacial times, conditions may not have been favorable for speleothem formation. …

Uranium-series Chronology and Environmental Applications of Speleothems

Earliest humans in Europe: the age of TD6 Gran Dolina, Atapuerca, Spain.

Electron spin resonance (ESR) dating

Les apports de la datation par resonance de spin electronique de l'email des dents a la chronologie des sites a hominides et ses implications pour la datation des origines de l'Homme moderne en Europe, au Proche-Orient et en Afrique

Electron spin resonance dating and the evolution of modern humans

Electron spin resonance (ESR) dating and ESR applications in quaternary science and archaeometry

OPTICAL and electron paramagnetic resonance (EPR) properties of natural and synthetic calcite (limestone, CaCO3) have been studied extensively and it is known that ionising radiation in the form of cosmic rays or from radioactive elements introduces defects such as CO3− (a hole centre) and CO33− (an electron centre), which are stabilised by impurities to form sources of thermoluminescence1,2. There are four thermal glow peaks above room temperature3,4, some of which can be used to trace the history of calcite5. Here I report the presence of a radiation-induced defect in the growing stalactites of Japan's main calcite caverns and show that estimation of the accumulated defect concentration at several positions, using EPR, makes it possible to determine the age and growth rate of a stalactite.

Dating a stalactite by electron paramagnetic resonance

The total dose of natural radiation and the age were determined from paramagnetic defects in quartz grains at a fractured fault zone. Young age at the fault indicates that the accumulated defects in rocks were destroyed by high stress or high temperature at the time of the last fault movement, setting the clock time to zero. The technique was applied to quartz grains crushed by uniaxial compression in the laboratory to verify this interpretation.

https://science.sciencemag.org/content/sci/215/4538/1392.full.pdf

Dating of a fault by electron spin resonance on intrafault materials.

Ages of fossil bones were determined by electron spin resonance spectroscopy. The electron spin resonance signal is associated with lattice defects or trapped centers produced by natural radiation in the bones and gives a measure of the total dose of natural radiation, or the archeological dose. Archeological doses were determined for samples of known age from a variety of sites and used to estimate apparent average annual rates of natural radiation at the sites. The method has the advantage that the sample need not be ground or heated, and it should be useful for dating biological materials.

https://science.sciencemag.org/content/sci/207/4434/977.full.pdf

Electron Spin Resonance Dating of Animal and Human Bones

Electron spin resonance (ESR) dating of sea shells has been made using the paramagnetic defects produced by natural radiation. The total dose of natural radiation of the materials, termed the archaeological dose, has been determined from ESR signals of defects in sea shells from northern Japan whose ages are known from the sediments or from the radioisotope dating. An annual dose of about 0.03-0.04 rad/yr explains the age of shells from a few thousand to a million years. The new method of ESR dating will be useful for sediment age determination and for other geological studies.

Motoji Ikeya

Papers

Dating a stalactite by electron paramagnetic resonance

Dating of a fault by electron spin resonance on intrafault materials.

Electron Spin Resonance Dating of Animal and Human Bones

Dating of Fossil Shells with Electron Spin Resonance

Comparison of ESR ages of corals from marine terraces with 14C and 230Th/234U ages