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Radioactivity and Matter
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
The radiocarbon dating technique is applicable to any biological material whose death corresponds to a time of interest to archaeologists. Thousands of samples have now been dated with such significance that results from “preradiocarbon” datings have become obsolete. Charcoal, wood, bone, leather, textiles, ropes and fibers are among the materials which have been used to date archaeological sites.
Questions and Answers
Published in Giulio Fanti, Pierandrea Malfi, of Turin, 2019
Giulio Fanti, Pierandrea Malfi
Apart from these notes, from a scientific point of view it must be observed that the radiocarbon dating method (Section 4.1) does not always furnish reliable data. Expert scientist W. Meacham wrote that a nonnegligible percentage of results are wrong principally due to external contamination of the sample. For example, as mentioned in Section 4.3, analysis on the Egyptian mummy n.1770 preserved in the Manchester Museum furnished different dates for bones and bandages—the latter resulting 800–1000 years younger than the former because of external contamination. Another example refers to the dating of young shells (Melanoides tuberculatus) that were classified as about 27,000 years old due to external contamination.
The evolution of Earth as a planet
Published in Aleksey B. Ptitsyn, Lectures in Geochemistry, 2018
Isotope analysis is one of the tools used to determine the age and genesis of geological bodies (and, hence, to study their evolution). Along with paleontology, which gives a relative age, radioisotope dating is used to determine the absolute age (specifically, radiocarbon dating and other kinds of analysis using potassium–argon, uranium–lead, rubidium– strontium, etc.). The observed ratios of stable isotopes of some elements (O, H, C, S,) allow us to draw conclusions about the origin of their compounds, taking into account redistribution of stable isotopes that occurs during different geochemical processes. Separation of stable isotopes is caused not only by their different atomic weights but also by different thermodynamic characteristics (free energy of formation). Therefore, isotope separation can also occur during chemical reactions, being very slow because the ΔG of the reactions differs from unity only slightly. For example, for the isotopic exchange reaction: 15NH3 + 14NH4+ = 14NH3 + 15NH4+ the equilibrium constant at 25°C equals 1.034.
Tectonic activity and the history of Wairau Bar, New Zealand’s iconic site of early settlement
Published in Journal of the Royal Society of New Zealand, 2019
As mentioned above, Polynesians arrived in New Zealand about 800 years ago (Anderson 2014). Except for the date assigned to the earlier event by Clark et al. (2015) (between about CE 1070 and CE 1150), Event 1 could have given rise to the Māori tradition described above—the subsidence possibly being enough to explain the reference in the Māori traditions to the creation of the lagoons (King et al. 2017). The dates for Event 1 are on samples that stratigraphically bracket the event. Dates measured to fix the younger age limit of Event 1, however, are on unidentified wood fragments (Clark et al. 2015), and thus have an unknown and possibly large inbuilt age, making them unsuitable for defining a minimum age (McFadgen 1982). Those for the older age limit are on peat, reeds and plant fragments from a peaty palaeosol stratigraphically just below the tsunami deposit (Clark et al. 2015). The boundary between the tsunami deposit and upper surface of the palaeosol is a sharp contact, interpreted as probably a result of scouring removing the upper surface of the palaeosol (Clark et al. 2015), which would expose older organic matter in the soil. Furthermore, radiocarbon dating buried soil organic matter usually overestimates the true date of burial (Wang et al. 1996). It is likely, therefore, that the dates on the peat (NZA36394), the reeds (NZA53727) and the plant fragments (NZA55432) all therefore have inbuilt age (Figure 5), but how much inbuilt age is difficult to quantify. The radiocarbon dates for Event 1 thus provide a maximum date of about CE 1070 with an unknown inbuilt age for the event, but not a minimum date (Figure 5).
The pollen record from marine core MD03-2607 from offshore Kangaroo Island spanning the last 125 ka; implications for vegetation changes across the Murray-Darling Basin
Published in Australian Journal of Earth Sciences, 2021
P. De Deckker, S. van der Kaars, S. Haberle, Q. Hua, J.-B. W. Stuut
Vegetation records from deep-sea cores, which commonly have a continuous deposition of sediments, can also be compared with other marine proxies such as sea-surface temperature (SST) signals. These sequences can be precisely dated by oxygen-isotope stratigraphies based on the composition of foraminifera linked to global chronologies (tuned to astronomical ages), enabling chronological control well beyond the limits of radiocarbon dating. In addition, other continental proxies obtained from the same core such as airborne dust, river clays and their geochemical composition, can be compared against the pollen record to better define environmental changes both on land and at sea.