scholarly journals OSL age determinations of Pleistocene fluvial deposits in Central Amazonia

2010 ◽  
Vol 82 (3) ◽  
pp. 691-699 ◽  
Author(s):  
Emílio A.A. Soares ◽  
Sonia H. Tatumi ◽  
Claudio Riccomini
Keyword(s):  
Amazon Basin ◽  
Luminescence Dating ◽  
Fluvial Deposits ◽  
Promising Tool ◽  
Geological Processes ◽  
Dating Methods ◽  
Depositional Process ◽  
Central Amazonia ◽  
Absolute Dating ◽  
Amazonian Region

Absolute dating methods have been used in chronological studies of geological processes and sedimentary units of Quaternary age in Central Amazonia, Brazil. Although radiocarbon dating has been very useful in archaeological research and soil studies, the temporal interval of this method is inefficient in evaluating the sedimentation aspects and geological events from the beginning of the Quaternary in the Amazon basin. The use of crystal luminescence dating has been one of the most promising tool for determining the absolute dating of Quaternary deposits in the Amazonian region. Optically stimulated luminescence (OSL) dating, following the MAR and SAR protocols, in a tectonic-sedimentary study of Quaternary fluvial deposits in the confluence area of the Negro and Solimões rivers, indicated ages from 1.3 (Holocene) to about 67.4 kyears (Late Pleistocene) for these sediments. Low radioactive isotope concentrations were found about 2ppm for 235U and 238U; 5ppm for 232Th; and the 40K concentrations were almost zero. A comparison was made between MAR and SAR protocols taking into account the fluvial depositional process.

Multi-proxy studies of the Late Glacial fluvio-aeolian succession in the type site Mierzyn, central Poland 

2021 ◽  
Author(s):  
Moska Piotr ◽  
Sokołowski Robert ◽  
Jary Zdzisław ◽  
Zieliński Paweł ◽  
Raczyk Jerzy ◽  
...  
Keyword(s):  
Western Europe ◽  
Late Glacial ◽  
Luminescence Dating ◽  
Climate Conditions ◽  
Central Poland ◽  
Depositional Processes ◽  
Dating Methods ◽  
Absolute Dating ◽  
Absolute Age ◽  
Pedogenic Processes

<p>Multi-proxy studies (including sedimentological, pedological, radiocarbon and optically stimulated luminescence dating methods) were used to establish origin and chronology of depositional processes in the type section Mierzyn, central Poland. The investigated key site is located in the extraglacial zone of the Last Glaciation, ca. 130 km to the south from the Last Glacial Maximum in the Luciąża river valley area. In the studied profile (16 m thick) two lithofacial complexes were identified. The lower, fluvio-aeolian complex consists of silty-sandy sediments (1.6 m) deposited. The final phase of fluvio-aeolian deposition is expressed by initial pedogenic processes. Above is located aeolian complex (13 m of thickness). Three aeolian units are separated by two palaeosols.</p><p>To establish stratigraphic framework of depositional and pedogenic processes, four samples for radiocarbon dating from palaeosols and twelve samples for OSL dating from sandy units were collected. The obtained results reveal very good agreement of both absolute dating methods. It led to reconstruct chronology of main palaeoenvironmental changes. The fluvio-aeolian complex and the lowermost part of aeolian complex (below the lower palaeosol) were deposited in the Oldest Dryas in relatively cool and dry climate conditions. The amelioration of climate in the Bølling interstadial caused development of pedogenic processes expressed by 0.3 m thick palaeosol. Main part of aeolian complex (10 m of thickness) was deposited in the Older Dryas. The upper palaeosol developed in the Allerød interstadial as a result of the next amelioration of the climate. During the Younger Dryas was deposited the uppermost part of aeolian complex.</p><p>Classic development of fluvial to- aeolian succession in the Mierzyn site as well as detailed chronology based on two independent absolute age methods reveal that it can be treated as stratotype for the Late Glacial and correlated with other type sections in the Central and Western Europe.</p><p><strong>Ackowledgments</strong></p><p>Presented results were obtained with support of Polish National Science Centre, contract number 2018/30/E/ST10/00616.</p><p> </p>

scholarly journals Geographic distance and vegetation structure rather than river barrier drive ant beta diversity across Central Amazonia

2021 ◽  
Author(s):  
Diego Rodrigues Guilherme ◽  
Pedro Aurélio Costa Lima Pequeno ◽  
Fabrício Beggiato Baccaro ◽  
Elizabeth Franklin ◽  
Cláudio Rabelo dos Santos Neto ◽  
...  
Keyword(s):  
Indirect Effects ◽  
Vegetation Structure ◽  
Beta Diversity ◽  
Amazon Basin ◽  
Isolation By Distance ◽  
Geographic Distance ◽  
Effect Of Temperature ◽  
Detectable Effect ◽  
Direct And Indirect Effects ◽  
Central Amazonia

Abstract To understand better the effects of niche and neutral processes is important to disentangle the direct and indirect effects of each process, mainly if the environmental factors are geographically structured neglecting important indirect and synergic effects. We sampled ground-dwelling ant species on 126 plots distributed across eight sampling sites along a broad environmental gradient in Central Amazonia. Structural equation modelling was employed to quantify direct and indirect effects of geographic distance, the Amazon River’s opposite margins, and environmental differences in temperature, precipitation and vegetation structure (Normalized Difference Vegetation Index) on ant beta diversity (Jaccard’s dissimilarity). We found that geographic distance and NDVI differences had major direct effects on ant beta diversity. The major effect of temperature was indirect through NDVI, whereas precipitation had no detectable effect on beta diversity. The Amazon River had a weak influence on the ant composition dissimilarity. Our results challenge the major role often ascribed to riverine barriers in the diversification and distribution of Amazonian biota. Rather, ant compositional dissimilarity seems to be mainly driven by a combination of dispersal limitation and selection imposed by vegetation features and, indirectly, by temperature. We suggest that as NDVI differences decrease with geographic distance in the region, isolation by distance may have favoured phenotypic convergence between ant communities in the northern and southern borders of the Amazon Basin.

scholarly journals 240+239Pu depositional signatures as a viable geochronological tool in the Amazon Basin

2017 ◽  
Vol 44 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Luciana M Sanders ◽  
Kathryn H Taffs ◽  
Debra Stokes ◽  
Alex Enrich-Prast ◽  
Christian J Sanders
Keyword(s):  
Amazon Basin ◽  
Environmental Science ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Recent Sediment ◽  
Floodplain Lake ◽  
Accumulation Rates ◽  
Amazon Floodplain ◽  
Dating Methods ◽  
Lead 210

AbstractAnthropogenic radionuclide signatures associated with nuclear testing are increasingly utilized in environmental science to explore recent sedimentation. In this study, we assess the suitability of Pu radioisotope analysis in floodplain lake environments in the Amazon Basin to form geochronologies during the 20thcentury. The240Pu +239Pu (240+239Pu) signatures in six sediment cores indicate sediment accumulation rates in the floodplain lakes of the major rivers; Amazon (2.3 mm year-1), Tapajos (10.2 and 2.4 mm year-1) and Madeira (3.4, 4.2 and 6.2 mm year-1). The results from this study show that240+239Pu fallout activities, and the well documented (240Pu/239Pu) atomic ratios of the above ground nuclear tests which began in the 1950’s, are sufficient and well preserved in Amazon floodplain lake sediments to infer chronologies. Lead-210 dating analyses in the same sediment cores produced comparable sediment accumulation rates at three of the six sites. The differences between dating methods may be attributed to the different time scale these dating methods represent and/or in the solubility between Pb and Pu along the sediment column. The geochronologies derived from the240+239Pu and210Pb dating methods outlined in this work are of interest to identify the effects of changing sediment accumulation rates during the previous century as a result of development, including deforestation, along the Amazon Basin which increased towards the middle of the 20thcentury. This study shows that Pu dating provides a viable alternative geochronology tool for recent sediment accumulation (previous ~60 years) along the Amazon Basin.

scholarly journals Luminescence Dating of Fluvial Deposits from the Weser Valley, Germany

2015 ◽  
Vol 42 (1) ◽  
Author(s):  
Julia Roskosch ◽  
Sumiko Tsukamoto ◽  
Manfred Frechen
Keyword(s):  
Late Pleistocene ◽  
Luminescence Dating ◽  
Marine Isotope Stage ◽  
Coarse Grained ◽  
Performance Tests ◽  
Luminescence Signal ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Infrared Stimulated Luminescence ◽  
Off Time

Abstract Luminescence dating was applied on coarse-grained monomineralic potassium-rich feld-spar and polymineralic fine-grained minerals of five samples derived from fluvial deposits of the Riv-er Weser in northwestern Germany. We used a pulsed infrared stimulated luminescence (IRSL) single aliquot regenerative (SAR) dose protocol with an IR stimulation at 50°C for 400 s (50 μs on-time and 200 μs off-time). In order to obtain a stable luminescence signal, only off-time IRSL signal was rec-orded. Performance tests gave solid results. Anomalous fading was intended to be reduced by using the pulsed IRSL signal measured at 50°C (IR50), but fading correction was in most cases necessary due to moderate fading rates. Fading uncorrected and corrected pulsed IR50 ages revealed two major fluvial aggradation phases during the Late Pleistocene, namely during marine isotope stage (MIS) 5d (100 ± 5 ka) and from late MIS 5b to MIS 4 (77 ± 6 ka to 68 ± 5 ka). The obtained luminescence ages are consistent with previous 230Th/U dating results from underlying interglacial deposits of the same pit, which are correlated with MIS 7c to early MIS 6.

scholarly journals Mortar Dating Methodology: Assessing Recurrent Issues and Needs for Further Research

Radiocarbon ◽  
2017 ◽  
Vol 59 (6) ◽  
pp. 1859-1871 ◽  
Author(s):  
Roald Hayen ◽  
Mark Van Strydonck ◽  
Laurent Fontaine ◽  
Mathieu Boudin ◽  
Alf Lindroos ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Optically Stimulated Luminescence ◽  
Archaeological Sites ◽  
Preparation Methods ◽  
Dating Methods ◽  
Absolute Dating ◽  
Set Up ◽  
Intercomparison Study ◽  
Sample Preparation Methods ◽  
Historic Stone

AbstractAbsolute dating of mortars is crucial when trying to pin down construction phases of archaeological sites and historic stone buildings to a certain point in time or to confirm, but possibly also challenge, existing chronologies. To evaluate various sample preparation methods for radiocarbon (14C) dating of mortars as well as to compare different dating methods, i.e. 14C and optically stimulated luminescence (OSL), a mortar dating intercomparison study (MODIS) was set up, exploring existing limits and needs for further research. Four mortar samples were selected and distributed among the participating laboratories: one of which was expected not to present any problem related to the sample preparation methodologies for anthropogenic lime extraction, whereas all others addressed specific known sample preparation issues. Data obtained from the various mortar dating approaches are evaluated relative to the historical framework of the mortar samples and any deviation observed is contextualized to the composition and specific mineralogy of the sampled material.

scholarly journals The archaeomagnetic field recorded in ancient kiln walls in Si Satchanalai, Sukhothai

2021 ◽  
Vol 2145 (1) ◽  
pp. 012049
Author(s):  
R Supakulopas
Keyword(s):  
Magnetic Field ◽  
Confidence Limit ◽  
Field Model ◽  
Luminescence Dating ◽  
Human History ◽  
Earth’S Magnetic Field ◽  
Argon Dating ◽  
Dating Methods ◽  
Earth's Magnetic Field ◽  
The Mean

Abstract Archaeological dating is crucial in archaeology as it is a key to understand human history. However, traditional dating methods used by archaeologists such as potassium-argon dating and luminescence dating can provide ambiguous age results, e.g., argon loss during the dating returns young apparent ages. Therefore, I plan to establish an archaeomagnetic secular variation (ASV) curve to resolve this problem and use the ASV curve as an alternative tool to date archaeological artefacts. However, archaeomagnetic data in Thailand are absent from literature. Therefore, the ASV curve cannot be constructed from the archaeomagnetic data for this locality. To provide archaeomagnetic data to construct the ASV curve, the directions of the Earth’s magnetic field recorded in kiln walls from Ban Ko Noi (KN123, age 1,370 ± 100 A.D.), Si Satchanalai were measured. The mean declination and inclination of 49.6° and 32.6° with 95% confidence limit of 5.4° were determined from 10 samples from kiln KN123. Mean directions from this study were also compared with the directions of the Earth’s magnetic field in Thailand during 1,370 A.D. from the global archaeomagnetic field model ARCH3k.1. Declination and inclination from this study show significant departure from the field predicted by the ARCH3k.1 model.

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