Radiocarbon Dating (Earth Sciences)

A workshop on bomb radiocarbon age validation for tuna and billfish in the Western and Central Pacific Ocean (WCPO) was held in early July 2020. Experts in otolith ageing and bomb radiocarbon methods discussed the encouraging results from preliminary radiocarbon work for tuna and agreed that the application of radiocarbon methods to validate age estimates derived from tuna and billfish otoliths from the WCPO was feasible. A design study was developed, using available otolith samples from the WCPFC Tuna Tissue Bank and other collections, and a draft research plan is proposed for consideration at SC16 (Appendix C). The recommendations from the workshop include that the:
• SC16 note the proposed research plan to continue the bomb radiocarbon age validation for bigeye tuna.
• SC16 note the proposed research plan for bomb radiocarbon age validation for yellowfin tuna.
• SC16 consider supporting these research plans with a budget contribution of USD97,980 (Appendix
C)

Estimates of age and growth of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna remain problematic because validation of growth zone deposition (opaque and translucent) has not been properly evaluated. Otolith growth structure (zone clarity) can be poorly defined for tropical tunas, but the use of bomb radiocarbon dating has validated age estimates to 16-18 years for yellowfin and bigeye tuna. Use of the radiocarbon decline period-defined by regional coral and otoliths-provided valid ages through ontogeny. Yellowfin tuna aged 2-18 years (n = 34, 1029-1810 mm FL) and bigeye tuna aged 3-17 years (n = 12, 1280-1750 mm FL) led to birth years that were coincident with the bomb radiocarbon decline. The results indicate there was no age reading bias for yellowfin tuna and that age estimates of previous studies were likely underestimated for both species.

Aragonite is one of the metastable polymorphs of calcium carbonate and is commonly found at archaeological sites in the form of mollusk shells and speleothems. Other occurrences include corals, fish otoliths, seed endocarps, wood ash and lime plaster. These materials contain microscopic embedded information of fundamental importance for the assessment of the state of preservation of the archaeological record, the reconstruction of paleoenvironments, the identification of pyrotechnological processes and the establishment of absolute chronologies. However, this information can be used only if the aragonite found at archaeological sites preserves its pristine structure and chemistry. Aragonite is metastable at ambient conditions and tends to dissolve and recrystallize into secondary aragonite or calcite, a process that entails the loss of its original elemental and isotopic signature. Therefore, well-grounded archaeological interpretations depend on the correct identification of aragonite and the careful characterization of its basic properties. This article aims at reviewing the dissolution processes of different types of aragonite, the methods used for their identification, and the archaeological information that can be extracted. Particular emphasis is given to the discussion of key issues regarding absolute dating and post-depositional processes of archaeological sediments, and to a detailed overview of the recently observed pyrogenic aragonite.

... Localización: La cueva de El Sidrón (Borines, Piloa, Asturias): investigación interdisciplinar de un grupo neandertal / coord. por Marco de la Rasilla Vives, 2011, ISBN 978-84-8053-602-8 , págs. 159-166. Fundación Dialnet. Acceso de usuarios registrados. ...

Excavations of the remains of the medieval church of Santa Maria di Campogrosso (Sicily) were conducted by the Institute of Archaeology and Ethnology of the Polish Academy of Sciences as part of scientific cooperation with Soprintendenza per i Beni Culturali ed Ambientali di Palermo. Based on the records of post-medieval historians, the construction of the church was placed in the second half of the 11th century, which contradicts the findings of architectural historians, who dated the building to the 13th-century and even later. As a result of archaeological excavations carried out in 2015–2018, it was possible to locate unknown fragments of the church’s structure and the remains of the cemetery adjacent to it. The ¹⁴ C dating carried out for samples obtained from the walls of the existing building as well as from bone remains from the churchyard in combination with stratigraphic information from archaeological trenches and the chronology of coins indicates a high probability of the church construction in the second half of the 12th century and confirms the end of the monastery complex existence at the end of the 13th century.

Previously published AMS radiocarbon ages for charcoal obtained from a stratigraphic profile at Wet Cave (5U10), Naracoorte World Heritage Area, southeastern South Australia (Pate et al. 2002), suggested that a range of megafauna disappeared from the site by ca. 45,000 years ago. The Wet Cave radiocarbon chronology provided additional data to support claims for a continent-wide extinction of megafauna in Australia by about 46,000 years ago (See Miller et al. 1999, 2005; Roberts et al. 2001; Johnson and Prideaux 2004; Johnson 2005). Here we report an additional eight AMS radiocarbon ages for charcoal from the same stratigraphic sequence at Wet Cave in order to provide other researchers with access to the expanded dataset.

A mathematical model, developed earlier in the Polar Geophysical Institute, is applied to investigate the transformation of global gas flows in the Earth's atmosphere over the course of a year. The model is based on the numerical solution of the system of gas dynamic equations. The mathematical model produces three-dimensional distributions of the gas dynamic parameters of the atmosphere in the height range from 0 to 126 km over the Earth's surface. To investigate the seasonal transformation of the global circulation of the lower and middle atmosphere, simulations are performed for conditions corresponding to twelve dates, which belong to twelve different months. Results of simulations indicated that the variations of the solar illumination of the Earth's atmosphere, conditioned by different positions of the Earth along its trajectory around the Sun, influence considerably on the transformation of the planetary circulation of the lower and middle atmosphere over the course of a year.

cave shrimps of the Typhlatya genus are common and widespread in fresh, brackish and marine groundwater throughout the Yucatan peninsula (Mexico). these species are ideal models to test niche partitioning within sympatric species in oligotrophic systems. nevertheless, their food sources remain unidentified, and despite their frequency and functional importance, distribution and abundance patterns of these species within caves have not been fully recognized. Here, we describe the abundance of three Typhlatya species in different temporal and spatial scales, investigate changes in water conditions, and potential sources of carbon as an indication of food origin. Species composition and abundance varied markedly in space and time revealing patterns that differed from one system to another and in relation to environmental parameters. isotope analysis showed that each species reflects a particular δ 13 C and Δ 14 C fingerprint, suggesting they feed in different proportions from the available carbon sources. Overall, our findings suggest a niche partitioning of habitat and feeding sources amongst the three Typhlatya species investigated, where environmental characteristics and physiological differences could play an important role governing their distribution patterns. The lack of photosynthesis in caves and the resulting limitation in food sources is one of the strongest selection pressures and drivers of evolution for life in caves 1. Competition for nutrients in oligotrophic environments, such as anchialine ecosystems-defined as subterranean estuaries that extend inland to the limit of seawater penetration 2 , certainly requires a unique set of specialization traits that allow for niche partitioning amongst stygobionts (aquatic species strictly bound to the subterranean habitat). A closer look at stygobiont biodiversity reveals that co-occurrence of sympatric species within the same system is rare but can be occasionally observed 3,4. This work gathers evidence that suggests how three sympatric cave shrimp species that coexist in groundwater ecosystems have partitioned their niche to avoid competitive exclusion. Groundwater in the anchialine systems of Yucatan is vertically stratified by the intrusion of marine water from the coast which inserts below the freshwater that constantly flows towards the coast 2. This marked halocline, along with changes in temperature, dissolved oxygen, pH and redox potential has been considered a physicochemical barrier that separates freshwater and saline communities 5,6. This stratification is expected in coastal systems, and as distance from the coast increases, the marine intrusion is found deeper and only a few deep cenotes inland may reach the saline layers 7. In terms of energy production and food webs, the sun-influenced cenote pools-cenote is a Mayan derived name for local sinkholes-are the only sites where photosynthesis can take place and allochthonous organic matter can enter the system. Therefore, these ecosystems have been historically regarded as dependent of open 1 Posgrado en Ciencias Biológicas, Unidad de Posgrado, Edificio A, 1er piso,

Giant trevally (Caranx ignobilis) are an iconic reef fish of the Indo-Pacific, and yet knowledge of their life history is incomplete. The species is common in tropical and subtropical waters ranging from the far western Indian Ocean off South Africa to the central Pacific Ocean, where the species attains its greatest recorded size in Hawaii. Despite their broad range, importance as a top predator and attraction among anglers, the age and longevity of giant trevally remain largely undescribed and there are concerns that giant trevally are being fished down in the Hawaiian Islands. The most comprehensive age and growth study was performed in the Hawaiian Islands, but the work was limited to early growth observations. Although a study of daily increments was limited to fish less than maximum size, a model used to describe the growth characteristics was extrapolated to estimate that maximum age may exceed 20 years. In this study, otoliths of giant trevally from the Hawaiian Islands were investigated for annual growth zones, and the validity of the age estimates was tested and validated with bomb 14C dating. Revised growth parameters indicate giant trevally grow rapidly in the Hawaiian Islands and can attain an age of 25 years.

Age of the human footprints in Sagyeri area, Jeju Island, Korea has been a subject of controversies since the discovery in 2004. This study reports a new basaltic tephra layer beneath the human footprints-bearing strata, and infers the source volcano of the tephra by comparing the major element composition of the glass and the componentry of accidental grains with those of the two nearby volcanic edifices (Songaksan volcano and Hyeongje Island) in addition to stratigraphic observations. Then we constrain the deposition age of the human footprints-bearing strata above the tephra layer, via revealing the eruption age of its source volcano. We found that the tephra layer at the footprints site is not only stratigraphically equivalent to the tephra rim beds of the Songaksan volcano but also compositionally identical to the glass in the major element content. Accidental quartz grains, which occur characteristically within the Songaksan Tuff, are also found in the tephra layer beneath the human footprints-bearing strata. These results suggest collectively that the tephra layer beneath the footprints-bearing strata was produced by the eruption of the Songaksan volcano. A set of new age data from the paleosol

Today, accelerator mass spectrometry (AMS) technology enables us to carry out very precise measurements of radiocarbon (14 C). Unfortunately, due to fluctuations in the 14 C calibration curve, the resulting calibrated time intervals vary from decades up to centuries in calibrated age. Within a time scale of several decades, we can find several time intervals on the 14 C calibration curve which correspond with periods of rapid increases in atmospheric 14 CO 2 activity. Some of these "high slope" parts of the calibration curve could be used for fine time resolution for radiocarbon dating of individual samples. Nevertheless, there are certain limitations owing to the properties of the samples measured. We have prepared a time-resolution curve for the 14 C dating method, applying calibration curve IntCal13 and assuming an uncertainty of 14 C analyses ±15 yr BP (for recent samples). Our curve of the time resolution covers the last 50 ka. We found several time intervals with time resolution below 50 yr BP for the last 3 ka. Several time intervals which can enable substantially better time resolution compared to neighboring parts of the calibration curve were also found for periods older than 3 ka.

The impact of rapid climate change on contemporary human populations is of global concern. To contextualize our understanding of human responses to rapid climate change it is necessary to examine the archeological record during past climate transitions. One episode of abrupt climate change has been correlated with societal collapse at the end of the northwestern European Bronze Age. We apply new methods to interrogate archeological and paleoclimate data for this transition in Ireland at a higher level of precision than has previously been possible. We analyze archeological (14)C dates to demonstrate dramatic population collapse and present high-precision proxy climate data, analyzed through Bayesian methods, to provide evidence for a rapid climatic transition at ca. 750 calibrated years B.C. Our results demonstrate that this climatic downturn did not initiate population collapse and highlight the nondeterministic nature of human responses to past climate change.