1,721,185 research outputs found
Dendrochronology and Radiocarbon – A perfect match
No full textABSTRACT
Tree-ring chronologies play a key role in the calibration of radiocarbon ages to calendar years. Over the past six decades close collaboration between dendrochronologists and isotope physicists resulted in multi-millennia long tree-ring chronologies, now reaching back to 14.226 years BP. Annual 14C variability, in addition to known cycles of the solar dynamo. Fluctuations of 14C quences to a precision of a decade or less in the time range of tree-ring based 14 cosmogenic isotopes, 14C and 10Be can be used to create segments of high-resolution 14C calibration over the past 50.000 years
A Comparison of Bone Pretreatment Methods for AMS Dating of Samples >30,000 BP
Get PDFBone is a commonly used material for radiocarbon dating, yet at ages close to the limit of the method (>30,000 BP), it is a substantial challenge to remove contamination and produce accurate ages. We report here on the preliminary results of a dating study of 2 bones older than 30,000 yr, which were each treated with a suite of pretreatment procedures, including ultrafiltration (Brown et al. 1988). Substantial differences in the C-14 ages were observed, which is most likely linked to crucial steps in the removal of contamination both in the bone and in the laboratory. Using a comprehensive sequence of pretreatment procedures, including ultrafiltration, we obtain generally older ages
THE FIRST RADIOCARBON-DATED REMAINS OF THE LEOPARD PANTHERA PARDUS (LINNAEUS, 1758) FROM THE PLEISTOCENE OF POLAND
Get PDFThe Pleistocene history of the leopard (Panthera pardus) in Europe has been documented by the material obtained from 312 localities, with the last dated similar to 1.1 Myr. The relatively small and gracile form of the leopard was very rare during the late Early and Middle Pleistocene. Only after the disappearance of the jaguar (Panthera gombaszoegensis) did P. pardus spread widely in Europe, increasing in size and ecologically substituting P. gombaszoegensis. The number of late Middle Pleistocene localities with leopard remains, younger than 300 kyr, increased considerably. The leopard reached the maximum extension of its geographical range in the Late Pleistocene. The Iberian Peninsula was the last European refuge for this cat. Six sites, the Naciekowa, Obok Wschodniej, Radochowska, and Wschodnia Caves from the Sudety Mountains and the Bisnik and Dziadowa Skala Caves from the Krakow-Czestochowa Upland, have documented the presence of the leopard in Poland between MIS 10/9 and MIS 3. These records are from rocky regions with rugged terrain and are located in the territory of Silesia (southern Poland). A newly obtained radiocarbon date (43-42 kyr) from the Radochowska Cave directly confirms the occurrence of P. pardus in the Sudety Mountains in the middle part of MIS 3
Radiocarbon calibration uncertainties for tree-ring chronologie Avigliana_A15
No full textRadiocarbon dating is the most commonly used chronological tool in archaeological and environmental sciences dealing with the past 50,000 years, making the radiocarbon calibration curve one of the most important records in paleosciences. For the past 12,560 years, the radiocarbon calibration curve is constrained by high quality tree-ring data. Prior to this, however, its uncertainties increase rapidly due to the absence of suitable tree-ring 14C data. Here, we present new high-resolution 14C measurements from 3 floating tree-ring chronologies from the last deglaciation. By using combined information from the current radiocarbon calibration curve and ice core 10Be records, we are able to absolutely date these chronologies at high confidence. We show that our data imply large 14C-age variations during the Bølling chronozone (Greenland Interstadial 1e) – a period that is currently characterized by a long 14C-age plateau in the most recent IntCal13 calibration record. We demonstrate that this lack of structure in IntCal13 may currently lead to erroneous calibrated ages by up to 500 years
The old bone project: Quality assurance on radiocarbon dating bone in the 30,000–50,000 age range at the A.E. Lalonde AMS Laboratory (Ottawa, Canada)
No full textA quality control program was undertaken to test the merit of different techniques for the preparation of Late Pleistocene bone at the A.E. Lalonde AMS Laboratory in Ottawa (Canada). The samples studied here include a mammoth bone (S-EVA 2000) previously dated by other labs (Oxford, Kiel, Mannheim) with results ranging between 35,280 and 31,660 14C yr BP (n = 10), a bison bone (S-EVA 2001) previously dated between 47,300 and 40,200 14C yr BP (n = 9; Talamo and Richards, 2011), and our in-house background standard (Hollis Mine Mammoth, HMM). Samples were prepared in four different ways: (1) no ultrafiltration and combustion by elemental analyser (EA); (2) ultrafiltration and EA combustion; (3) no ultrafiltration and quartz tube combustion; (4) ultrafiltration and quartz tube combustion. All four methods produced dates for the S-EVA 2000 bone between 34,530 and 34,080 14C yr BP (n = 7) and consistent stable isotope data (δ13C, δ15N, C:N). Results for the HMM bone ranged from 54,600 to 46,800 14C yr BP. Further, the S-EVA 2001 was prepared without ultrafiltration and combusted on the EA, resulting in a date of 45,010 ± 460 14C yr BP. Finally, since a major challenge with dating Late Pleistocene bone is to decipher between finite and infinite ages, we report results from two years of measurement of the HMM bone, which is prepared with each bone batch. The average age of the HMM is 50,700 ± 3400 14C yr BP (n = 17) when not ultrafiltered, and 48,400 ± 2900 14C yr BP (n = 13) when ultrafiltered. Results from this study do not reinforce or negate the use of ultrafiltration, but it was determined that combustion by EA is preferred as it gives %C and %N values
Stable isotopes in the shell organic matrix for (paleo)environmental reconstructions
Get PDFAbstract Stable isotope ratios of mollusc shell carbonates have long been used to reconstruct past environmental conditions. Although shells also contain organics, they are seldom used in (paleo)climatic studies. Here, we extract the acid-soluble and insoluble fractions of the organic matrix of modern Mytilus galloprovincialis shells from three sites along a coast–to-upper-estuary environmental gradient to measure their hydrogen (δ2H) and oxygen (δ18O) isotope compositions. Both organic fractions showed isotopic signatures significantly different from those of carbonate and water at each site, indicating the involvement of different fractionation mechanisms. The soluble fraction showed gradual differences in isotope values along the gradient, while the insoluble fraction showed δ2H-δ18O correlation regressions subparallel to the Global and Local Meteoric Water Lines. These results showed the great potential of the shell organic matrix stable isotopes as possible (paleo)environmental proxies, stimulating further research to better define the fractionation mechanisms involved
The Quaternary lions of Ukraine and a trend of decreasing size in Panthera spelaea
Get PDFThe fossil record of the cave lion, Panthera spelaea, suggests a gradual decrease in body size, the process peaking just before
the extinction of the species at the end of the Late Pleistocene. Such an evolutionary trend appears rather unusual for a large
felid species and requires further investigation. This study reviews the cave lions of Ukraine, whose fossils are known
from 46 localities dated from 800 kyr to 18–17 kyr ago, with a special emphasis on size changes through time. We describe
several important finds including those of Panthera spelaea fossilis from Sambir, Panthera spelaea ssp. from Bilykh Stin
Cave and Panthera spelaea spelaea from Kryshtaleva Cave. We make subspecific identifications of specimens from the region
and focus on their size characteristics. Our analysis of Ukrainian cave lions agrees with the temporal trend of decreasing
size, particularly accelerating during MIS 2, as exemplified by the extremely small female skull from Kryshtaleva Cave. We
provide a direct AMS date for this specimen (22.0–21.5 cal kyr BP), which suggests that the Kryshtaleva lioness must have
belonged to a Panthera spelaea spelaea population forced south by the spreading ice sheet. We discuss some palaeoecologi-
cal aspects of the evolutionary history and eventual extinction of the cave lion. Finally, we review the subfossil records of
the extant lion Panthera leo known from several Ukrainian sites archaeologically dated to 6.4–2.0 kyr BP. These finds most
probably represent the Persian lion Panthera leo persica
The olive branch chronology stands irrespective of tree-ring counting
No full textThe date of the volcanic eruption of Santorini
that caused extensive damage toMinoanCrete
has been controversial since the 1980s. Some
have placed the event in the late seventeenth
century BC. Others have made the case for a
younger date of around 1500 BC. A recent
contribution to that controversy has been the
dating of an olive tree branch preserved within
the volcanic ash fall on Santorini. In this
debate feature Paolo Cherubini and colleagues
argue that the olive tree dating (which
supports the older chronology) is unreliable on
a number of grounds. There follows a response
fromthe authors of that dating, and comments
fromother specialists,with a closing reply from
Cherubini and his team
Trees: radiocarbon and dendrochronology - together for the Resolution project
Get PDFThe year 14,226 BP marks an important border in the actual radiocarbon (14C) calibration curve: the high resolution and precision characterising the first part (0 – 14,226 BP) of the curve are due to the potential represented by tree-ring datasets, which directly provide the atmospheric 14C content at the time of tree-rings formation with high resolution. They systematically decrease going back in time, where only a few floating tree-ring chronologies alternate to other low-resolution records.
The lack of resolution in the dating procedure before 14,226 years BP leads to significant issues in the interpretation and untangling of tricky facts of our past, in the field of Human Evolution.
Research on sub-fossil trees and the construction of new Glacial tree-ring chronologies can significantly improve the radiocarbon dating in terms of temporal resolution and precision until 55,000 years BP to clear puzzles in the Human Evolution history.
In this thesis, the dendrochronological study, the radiocarbon dating and the extrapolation of environmental and climate information from sub-fossil trees found on the Portugal foreshore, remnants of a Glacial lagoonal forest, are presented.
The careful sampling, the dendrochronological measurements and cross-dating, the application of the most suitable cellulose extraction protocol and the most advanced technologies of the MICADAS system at ETH-Zurich, led to the construction of a new 220-years long tree-ring site chronology and to high resolution, highly reliable and with a tight error range radiocarbon ages.
At the moment, it results impossible to absolutely date this radiocarbon sequence by the comparison of Δ14C of the trees and 10 Be fluctuations from the ice-cores. For this reason, tree growth analysis, comparisons with a living pine stand and forest-fires history reconstruction have made it possible to hypothesize site and climate characteristics useful to constrain the positioning in time of the obtained radiocarbon sequence
Radiocarbon and stable isotopes in the shell organic matrix: a new approach for the use of mollusk shells in the study of human evolution
Get PDFMollusk shells are often found in archeological sites, given their great preservation potential and high value as a multipurpose resource. They are often the only available material to use for radiocarbon dating, due to a lack of well-preserved bones in many archeological sites, especially for the key period of the Middle to Upper Paleolithic transition. However, radiocarbon dating on mollusk shells is often regarded as less reliable compared to bones, wood, or charcoals due to the various factors influencing their radiocarbon content (e.g., Isotope fractionation, marine reservoir effect etc.). For the development of more accurate chronologies using shells, it is fundamental to continue improving the precision of the techniques applied, as has been done for other materials (wood and bones). Thus, improving the chemical pretreatment on mollusk shells might allow researchers to obtain more reliable radiocarbon determinations allowing for the construction of new radiocarbon chronologies in archeological sites where so far it has not been possible. Furthermore, mollusk shells can provide information on the climatic and environmental variables present during their growth. Using shells for paleoclimatic reconstruction adds more evidence helpful for the interpretation of scenarios of human migration, adaptation, and behavior. Standard methods for both radiocarbon and stable isotope studies use the carbonate fraction of the shell. However, being biogenic structures, mollusk shells also consist of a minor organic fraction. The shell organic matrix has an important role in the formation of the calcium carbonate structure and is still not fully understood. This thesis explores the potential of using the shell organic matrix for radiocarbon dating and paleoenvironmental studies. The results of the work performed for this thesis represent a starting point for future research to build on, and further develop the approach and methodology proposed here
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