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Dating the Tejo river lower terraces in the Ródão area (Portugal) to assess the role of tectonics and uplift

Cunha, Pedro P.; Martins, António A.; Huot, Sebastien; Murray, Andrew; Raposo, Luís
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
56.94%
The Tejo river is one of the major drainages in Iberian Peninsula; it is a long-lived system (ca. 3.4 Ma) and provides an archive of long-term landscape development and environmental change controlled by tectonics, climate and eustasy. The most upstream Portuguese reach of the Tejo river, ~ 200 km from the Atlantic coast, shows evidence for five fluvial terraces (T1 to T5) with elevations reaching more than 120 m above the modern river bed. A chronological framework for these terraces is established here by integrating geomorphological, stratigraphical and archaeological information with ages from luminescence dating. Optically stimulated luminescence dating of K-feldspar, (involving the correction for anomalous fading of the luminescence signal), indicates that the younger terraces have a probable age range of: T5 -- 31 to 40 ka; and T4 -- 100 to ~ 280 ka. We deduce that the related major fluvial changes are likely to have been as follows: ~ 10 m of aggradation from ~ 280 to 100 ka (0.06 m/ka); 14 m of incision from 100 to 40 ka (0.23 m/ka); 8 m of aggradation from 40 to 31 ka (0.89 m/ka); 16 m of incision during the last 31 ka (0.52 m/ka). These values indicate that the duration and rate of both aggradation and river downcutting episodes were variable. There is widespread evidence for neotectonic activity in this intraplate region. Neither eustatic nor climatic changes during the Quaternary provide clear trends that might explain the observed pattern of valley incision...

OSL age determinations of Pleistocene fluvial deposits in Central Amazonia

SOARES, Emílio A.A.; TATUMI, Sonia H.; Riccomini, Claudio
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.85%
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.; Métodos de datação absoluta têm sido usados em estudos cronológicos de processos geológicos e unidades sedimentares de idade quaternária na Amazônia Central...

How Old Is Luzia? Luminescence Dating and Stratigraphic Integrity at Lapa Vermelha, Lagoa Santa, Brazil

FEATHERS, James; KIPNIS, Renato; PILO, Luis; ARROYO-KALIN, Manuel; COBLENTZ, David
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.68%
During an excavation in the 1970s, a disarticulated female human skeleton, later nicknamed Luzia, was discovered at 12m depth at Lapa Vermelha rockshelter in central Brazil. Radiocarbon dating of associated charcoal suggested an age of 11.4-16.4 ka for the skeleton. The scattering of the skeletal parts, some uncertainty about the exact provenience of the skeleton, and evidence of pervasive insect turbation in the archaeological layers have raised doubts about the accuracy of the age. Luminescence dates for the depositional ages of the sediments at Lapa Vermelha are reported here. Single-grain optically stimulated luminescence (OSL) of quartz along with grain-size, chemical and micro-morphological analyses of the sediments were employed to assess stratigraphic integrity, particularly the degree of sediment mixing. These various lines of evidence point to high stratigraphic integrity with little mixing at Lapa Vermelha. Sediments closest to where Luzia was recovered give OSL ages ranging from 12.7 to 16.0 ka, thus not refuting the original dates. (C) 2010 Wiley Periodicals, Inc.

Depósitos costeiros quaternários do noroeste de Portugal (Minho - Neiva) : caracterização datação e interpretação paleoambiental; Quaternary coastal deposits of NW Portugal (Minho – Neiva area) : characterization, dating and paleoenvironmental interpretation

Carvalhido, Ricardo P.; Pereira, D. I.; Cunha, P.P.
Fonte: LNEG Publicador: LNEG
Tipo: Artigo de Revista Científica
Publicado em //2014 POR
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46.67%
Este estudo apresenta a caracterização e datação absoluta de depósitos costeiros quaternários do NW Portugal, situados entre a foz dos rios Minho e Neiva, definindo-se a litostratigrafia e propondo-se uma correlação com os Estádios Isotópicos Marinhos MIS9-MIS1. Foram identificados paleoambientes continentais (pequenos leques aluviais e de cursos de água) e de transição (dunas eólicas, lagoas interdunares, estuário, praias de areia e de seixo) datados através de Luminescência Opticamente Estimulada (Método SAR - quartzo e feldspato) e AMS 14C. Estes depósitos constituem 16 unidades litostratigráficas conservadas nas plataformas costeiras modeladas a ca. 13 m (terraço T2), a ca. 8 m (terraço T3) e ca. 3 m (terraço T5) (n.m.m.), definindo 3 formações: a Formação de S. Sebastião (T2), provavelmente correlativa do MIS9; a Formação da Estrada Real (T3), provavelmente correlativa do MIS7 e a Formação de S. Domingos (T5), com 4 membros (Cão, S. Domingos, Montedor e Galeão) e compreendendo o intervalo temporal do MIS5 ao MIS1.; This study presents the characterization and absolute dating of Quaternary coastal deposits of NW Portugal, between the mouths of the rivers Minho and Neiva, defines their lithostratigraphy and ascribes them to the interval MIS9-MIS1. The deposits record continental (small alluvial fans and streams) and transition paleoenvironments (eolian dune...

Dating the Tejo river lower terraces in the Ródão area (Portugal) to assess the role of tectonics and uplift

Cunha, P.,; Martins, A.; Huot, S.; Murray, A.; Raposo, L.,
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.94%
The Tejo river is one of the major drainages in Iberian Peninsula; it is a long-lived system (ca. 3.4 Ma) and provides an archive of long-term landscape development and environmental change controlled by tectonics, climate and eustasy. The most upstream Portuguese reach of the Tejo river, ∼200 km from the Atlantic coast, shows evidence for five fluvial terraces (T1 to T5) with elevations reaching more than 120 m above the modern river bed. A chronological framework for these terraces is established here by integrating geomorphological, stratigraphical and archaeological information with ages from luminescence dating. Optically stimulated luminescence dating of K-feldspar, (involving the correction for anomalous fading of the luminescence signal), indicates that the younger terraces have a probable age range of: T5 — 31 to 40 ka; and T4 — 100 to ∼280 ka. We deduce that the related major fluvial changes are likely to have been as follows: ∼10 m of aggradation from ∼280 to 100 ka (0.06 m/ka); 14 m of incision from 100 to 40 ka (0.23 m/ka); 8 m of aggradation from40 to 31 ka (0.89 m/ka); 16mof incision during the last 31 ka (0.52m/ka). These values indicate that the duration and rate of both aggradation and river downcutting episodeswere variable. There iswidespread evidence for neotectonic activity in this intraplate region. Neither eustatic nor climatic changes during the Quaternary provide clear trends that might explain the observed pattern of valley incision...

Geomorphological correlation of the tectonically displaced Tejo River terraces (Gavião–Chamusca area,central Portugal) supported by luminescence dating

Martins, A., Cunha, P., Huot, S., Murray, A., Buylaert, J.,
Fonte: Elsevier Ltd and INQUA Publicador: Elsevier Ltd and INQUA
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
67.02%
A suite of fluvial terraces (T1–T6,from top to bottom of the staircase) occur along a _70km stretch of the Tejo River in central Portugal, between the small towns of Gavião and Chamusca. Terrace correlation was based upon the following: (a)aerialphotograph analysis, geomorphological mapping and field topographic survey; (b) sedimentology of the terrace deposits, namely the maximum particle size, clast composition and lithofacies identification; and (c) K-feldspar infrared stimulated luminescence (IRSL) dating of the three lower terraces levels, as quartz optically stimulated (OSL) signal of the samples from these terraces was too close to saturation for all but two samples.The two upper terraces (T1andT2) lack suitable materials for luminescence dating (e.g.sands/silts),but also their probable ages are beyondthe upper range of the dating method. Fault saffecting terraces and older deposits have been reported. The luminescence dating results suggest that some assignments of local terrace remnants were in correct because of fault-related vertical displacements. The luminescence dating procedure also included a correction for anomalous fading in order to obtain more reliable estimates of the burial ages. The fading rate was identical for all samples...

K-feldspar IRSL dating of a Pleistocene river terrace staircase sequence of the Lower Tejo River (Portugal, western Iberia)

Martins, António; Cunha, Pedro; Buylaert, Jan Pieter; Huot, Sébastien; Murray, Andrew; Dinis, Pedro; Stokes, Martin
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
47%
We present the results of K-feldspar IRSL dating of the four lower terraces (T3–T6) of the Portuguese Tejo River, in the Arripiado-Chamusca area. Terrace correlation was based upon: a) analysis of aerial photographs, geomorphological mapping and field topographic survey; b) sedimentology of the deposits; and c) luminescence dating. Sediment sampled for luminescence dating gave unusually high dose rates, of between 3.4 and 6.2 Gy/ka and, as a result, quartz OSL was often found to be in saturation. We therefore used the IRSL signal from K-feldspar as the principal luminescence technique. The K-feldspar age results support sometimes complex geomorphic correlations, as fluvial terraces have been vertically displaced by faults (known from previous studies). Integration of these new ages with those obtained previously in the more upstream reaches of the Tejo River in Portugal indicates that the corrected K-feldspar IRSL ages are stratigraphically and geomorphologically consistent over a distance of 120 km along the Tejo valley. However, we are sceptical of the accuracy of the K-feldspar ages of samples from the T3 and T4 terraces (with uncorrected De values >500 Gy). In these cases the Dose Rate Correction (DRC) model puts the natural signals close to luminescence saturation...

CHRONOLOGY OF THE VALE DO FORNO FLUVIAL SEQUENCE AND ITS RELEVANCE TO LOWER PALAEOLITHIC IN W IBERIA

Martins, António; Cunha, Pedro; Buylaert, Jan-Pieter; Murray, Andrew; Mozzi, Paul; Raposo, Luis; Stokes, Martin
Fonte: Fluvial Archive Group (FLAG) Publicador: Fluvial Archive Group (FLAG)
Tipo: Aula
POR
Relevância na Pesquisa
46.71%
The Vale do Forno archaeological sites (Alpiarça, central Portugal) document the earliest human occupation in the River Tejo lower valley, well established in geomorphological and environmental terms, within the Middle Pleistocene. In a staircase of six fluvial terraces, the Palaeolithic sites were found on the T4 terrace that comprises a Lower Gravels basal unit (LG) and an overlying Upper Sands unit (US). Geomorphological mapping, coupled with lithostratigraphy, sedimentology and luminescence dating (quartz-OSL and K-feldspar post-IRIR290) were used in this study. The oldest artefacts found in the LG unit show crude bifacial forms that can be attributed to the Early Acheulian. In contrast, the US unit has archaeological sites documenting the Middle and Late Acheulian. Luminescence dating and correlation with the Marine Isotopic Stages suggest that the LG unit has a probable age of 340 to 330 ka and the US unit an age of ca. 330 to 160 ka. This discards previous interpretations ascribing this terrace (and its associated lithic industries) to the Last interglacial and early phases of the Last glacial. Only the VF3 site (Milharós), containing “Micoquian” (Final Acheulian) industries (with fine and elaborated bifaces) found in a level between the T4 terrace and a colluvium associated with Late Pleistocene aeolian sands...

OSL age determinations of Pleistocene fluvial deposits in Central Amazonia

Soares,Emílio A.A.; Tatumi,Sonia H.; Riccomini,Claudio
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
Relevância na Pesquisa
46.85%
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.

Luminescence dating of glaciofluvial deposits linked to the penultimate glaciation in the Eastern Alps

Bickel, Lukas; Lüthgens, Christopher; Lomax, Johanna; Fiebig, Markus
Fonte: Pergamon Press Publicador: Pergamon Press
Tipo: Artigo de Revista Científica
Publicado em 30/01/2015 EN
Relevância na Pesquisa
46.72%
During the penultimate glaciation vast areas of the Alps were glaciated, with piedmont glaciers protruding into the foreland. In the easternmost part of the northward draining valleys of the Alps, the glaciers did not reach the foreland, but formed valley glaciers confined by the mountainous terrain. This also applies to the Ybbs valley, where samples for luminescence dating out of glaciofluvial gravel accumulations were taken at three locations along the present day river course. In a highly dynamic depositional environment, such as a glacier-fed river system, incomplete resetting of the luminescence signal is possible, in particular when transport distances are short. In such cases, quartz usually is the preferred mineral over feldspar, especially if dose rates are low and may theoretically allow obtaining quartz ages beyond 150 ka. Because previous research has shown, and as corroborated within this study, quartz from the research area exhibits analytical problems in the high age range. Therefore luminescence properties of coarse grain (100–200 μm) quartz and in addition K-rich feldspar were investigated with the aim to reconstruct the chronology of the glacial processes within the Ybbs catchment area. Issues of incomplete bleaching were pIRIR225 encountered and addressed by comparing quartz OSL...

New luminescence ages for the Galería Complex archaeological site: resolving chronological uncertainties on the Acheulean record of the Sierra de Atapuerca, Northern Spain

Demuro, M.; Arnold, L.J.; Parés, J.M.; Pérez-González, A.; Ortega, A.I.; Arsuaga, J.L.; Bermúdez De Castro, J.M.; Carbonell, E.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
47.08%
The archaeological karstic infill site of Galería Complex, located within the Atapuerca system (Spain), has produced a large faunal and archaeological record (Homo sp. aff. heidelbergensis fossils and Mode II lithic artefacts) belonging to the Middle Pleistocene. Extended-range luminescence dating techniques, namely post-infrared infrared stimulated luminescence (pIR-IR) dating of K-feldspars and thermally transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains, were applied to fossil-bearing sediments at Galería. The luminescence dating results are in good agreement with published chronologies derived using alternative radiometric dating methods (i.e., ESR and U-series dating of bracketing speleothems and combined ESR/U-series dating of herbivore teeth), as well as biochronology and palaeoenvironmental reconstructions inferred from proxy records (e.g., pollen data). For the majority of samples dated, however, the new luminescence ages are significantly (∼50%) younger than previously published polymineral thermoluminescence (TL) chronologies, suggesting that the latter may have overestimated the true burial age of the Galería deposits. The luminescence ages obtained indicate that the top of the basal sterile sands (GIb) at Galería have an age of up to ∼370 thousand years (ka)...

Towards a quantification of environmental and climatic factors between 60 and 20 ka in SE Europe using geochemistry and luminescence dating

Schatz, Ann-Kathrin
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertação
EN
Relevância na Pesquisa
46.71%
To further or understanding of past climate changes and their impact on the environment in the younger geological past, Quaternary terrestrial deposits such as loess-paleosol sequences (LPSS) potentially contain valuable information and have long been recognized as excellent archives of paleoclimate data. However, many loess paleosol studies lack truly interdisciplinary and multi-proxy approaches, as well as information about the origin, transport and sedimentation history of the material, or reliable quantitative climatic information that has been cross-validated with independent data from other sources. The aim of this cumulative study was to combine and apply a wide range of traditional and innovative methods to a loess-paleosol sequence at Tokaj in Northeast Hungary, one of the key locations of loess research in Southeast Europe. In the first part, we provide the first complete chronostratigraphy for the section based on luminescence (OSL and IRSL) dating, which serves as a framework for all further analyses. Results show that previous age estimates were often too low, which may require a review of previous studies that rely on the now obsolete age model. Furthermore, this research also contributes to the introduction of pIRIR290 as a new luminescence dating technique with a substantially extended age range. Sedimentation rates calculated from the updates ages more than double during Marine Isotope Stage (MIS) 2 (29-14 ka) compared to MIS 3 (57-29 ka)...

Testing the TT-OSL single-aliquot protocol for quartz sediment dating.

Moffatt., Jillian Elizabeth
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
57.08%
Thermally-transferred optically stimulated luminescence (TT-OSL) is a form of optically stimulated luminescence that saturates at much higher doses than conventional OSL (Wang et al, 2006b). Luminescence sediment dating is a technique whereby the natural radiation dose given to a sample is measured. This is divided by the environmental radiation rate of the sample site to give the sample's age. As TT-OSL is able to measure higher doses than conventional OSL, it has been considered a candidate for long range luminescence sediment dating, beyond one million years. In this thesis, TT-OSL single-aliquot sediment dating protocols were tested on selected samples from the south-east of South Australia (SESA) stranded dune sequence, a sequence of ancient dunes ranging from 0 to 900 thousand years of age that have previously been independently dated using luminescence and non-luminescence dating methods. A young sample with a high natural dose from Baldina Creek, Burra, South Australia was also dated. Measurements of the thermal depletion of the TT-OSL signal were also made. It was found that, for the SESA samples, TT-OSL dating results do not agree with previous independent measurements above 200 ka. The results for the young Baldina Creek sample were within the expected range.; Thesis (M.Phil.) -- University of Adelaide...

Luminescence dating of spring mound deposits in the southwestern Great Artesian Basin, northern South Australia

Prescott, J.; Habermehl, M.
Fonte: Taylor & Francis Ltd. Publicador: Taylor & Francis Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
66.85%
Artesian spring mound deposits in the southwestern part of the Great Artesian Basin arise from groundwater discharge from flowing springs in the southern and western margins which reaches the surface through faults and weaknesses in thin confining beds overlying the Mesozoic artesian aquifers. Carbonate in solution in the artesian groundwater is deposited by many springs as tufa, building 'spring mounds.' Active flowing and dry inactive spring mounds occur in a variety of sizes and shapes. The ages of a representative selection of spring mound deposits have been found by luminescence dating of quartz sand grains that have been incorporated in the mound deposits. The spring deposits of the active flowing springs, Big Bubbler, Blanche Cup and Beresford Spring have ages of 15.1 ± 2.2, 10.9 ± 1.5 and 13.9 ± 1.0 ka, respectively. Spring complexes with both active flowing and dry extinct mounds, Strangways and Beresford Springs, have ages of 60 ± 8 and 219 ± 35 ka, respectively. Spring deposits of springs which ceased flowing and are overlying pedestals of Cretaceous Bulldog Shale and of substantial height (up to >45 m above the surrounding plain) of Beresford Hill and Kewson Hill gave ages of 128 ± 33 ka and 400 ± 100 ka, respectively. Elizabeth Springs is a large spring mound...

Luminescence dating: an Australian perspective

Prescott, J.; Robertson, G.
Fonte: Taylor & Francis Ltd. Publicador: Taylor & Francis Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
67.05%
Applications of luminescence dating to Quaternary earth science are reviewed, the examples being from Australia. The methods of thermoluminescence (TL) and optical dating using optically stimulated luminescence (OSL) are briefly described, together with their limitations. Prominent results are: (i) the distribution of ages of Australian desert dunes shows peak activity at about the time of the last glacial maximum; (ii) the lake-full episodes of Lake Eyre are traced back to 140 ka; (iii) the ages of relict beach dunes in South Australia, when compared with independent geological ages based on δ18O records, show that luminescence dating can be used for ages to 500 ka and older; and (iv) the development of interior river systems has been traced. Among less common applications are: (i) the dating of Australia's youngest volcanoes at 5-4 ka (in these cases the luminescence signal was reset by heat); (ii) the determination of age vs depth of a deep-sea core; and (iv) the age of earthquakes (from the age of the infilling of fault scarps). The emphasis is on recent work and is illustrative rather than exhaustive, the object being to show the scope of luminescence dating. There are suggestions where further research might be directed.; J. R. Prescott and G. B. Robertson

The storage of bed material in mountain stream channels as assessed using Optically Stimulated Luminescence dating

Thompson, Chris; Rhodes, Edward; Croke, Jacky
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.71%
A detailed understanding of channel forming and maintenance processes in mountain streams requires some measurement and/or prediction of bed load transport and sediment mobility. Traditional field based measurements of such processes are problematic becau

Luminescence dating of sand deposits related to late Pleistocene human occupation at the Cactus Hill Site, Virginia, USA

Feathers, James K; Rhodes, Edward; Huot, Sebastien; Mcavoy, Joseph M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.61%
Optically stimulated luminescence (OSL) ages, obtained primarily using single grains, are reported for 13 sediment samples from the Cactus Hill site, a culturally stratified sand dune in Virginia. The site has drawn interest because of a blade level, pote

Luminescence dating and glacial stratigraphy in Westland, New Zealand

Berger, Glenn W; Almond, P; Pillans, Bradley
Fonte: Sir Publishing Publicador: Sir Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.85%
Westland is a key region in New Zealand for Quaternary stratigraphy; however, the regional glacial chronology is largely unsupported by numerical ages because of the unreliability of radiocarbon dating in this high-rainfall region. Therefore, we tested the ability of thermoluminescence (TL) and infrared-stimulated luminescence (IRSL) to produce stratigraphically consistent age estimates in this area. At Blue Spur Road, we obtained a stratigraphically reasonable TL age of 47 ± 7 ka in the second buried E horizon and a perhaps underestimated 53 ± 16 ka in the lower part of the fourth buried Bs horizon. A marine sand underlying Waimea outwash gave an incorrect (underestimated) IRSL age of c. 44 ka. In Saltwater Forest we collected five samples from two loess profiles overlying glacial moraines. Only one TL age (36 ± 3 ka in the lower part of the first Bs horizon) is acceptable. The next lower sample (c. 1.2 m), stratigraphically probably younger than 125 ka, gave a reasonable IRSL age of 89 ± 15 ka. In trench M 1/1, on an older moraine, two TL age estimates were stratigraphically reversed, with a third result (87 ± 30 ka in unit L4) being reasonable. In contrast, IRSL produced ages of 65 ± 16 ka (1.1 m) and 145 ± 36 ka (2.0 m) for the upper two samples...

The Late Upper Palaeolithic Ocupation of the Moroccan Northeast Maghreb During the Late Glacial Maximum

Barton, R; Bouzouggar, A; Collcuttt, S; Gale, R; Higham, Thomas F. G.; Humphrey, L; Parfitt, S; Rhodes, Edward; Stringer, Chris; Malek, F
Fonte: Plenum Publishing Corporation Publicador: Plenum Publishing Corporation
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.67%
New work at Kehf el Hammar Cave provides the first well-dated palaeoenvironmental sequence for the Late Upper Palaeolithic in this region of the northwest Maghreb. The archaeological layers are dated via a combination of AMS radiocarbon and luminescence dating methods. The sequence contains charcoal-rich occupation layers with faunal, human and lithic finds. Local vegetational patterns are reconstructed on the basis of preliminary analysis of the charcoal evidence. Using standard calibration curves the AMS radiocarbon dates are compared with proxy evidence for climatic change from sea core records in the Alborán Sea. These appear to show that the Late Upper Palaeolithic occupation of the region coincides closely with Heinrich Event 1, a period marked by intense aridification and dating to ca. 16,700-17,250 calendar years ago.

Luminescence chronology of loess-paleosol sequences form southern South Island, New Zealand

Berger, Glenn W; Pillans, Bradley; Bruce, J G; McIntosh, P D
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.95%
The loess-paleosol sequences in New Zealand are among the thickest in the southern hemisphere, and preserve an important terrestrial record of paleoclimatic changes. Unlike loess-paleosol sequences in North Island, most of those in South Island lack discrete chronostratigraphic marker ash beds, excepting perhaps the widespread ∼24 ka Kawakawa Tephra. Therefore, any specific correlation to marine isotope stage (MIS) proxy records or to loess-paleosol sequences in the northern hemisphere has been unknown. Hence, we applied luminescence sediment dating to four key loess-paleosol sequences from southern South Island. Although these pioneering results suggest that further sampling and luminescence dating are needed, they do provide: (1) the first numeric age constraint (44±3ka on overlying loess) for the end of deposition of the geomorphically and paleoclimatically important Edendale Terrace gravels; (2) the first numeric evidence that the youngest loess-paleosol unit (L1) at the near-coastal Romahapa and inland Stewarts Claim sites began to be preserved much earlier (at ∼60 ka) than at the inland Kingston Crossing site (∼35 ka); (3) the first direct evidence that the 6 m Romahapa sequence extends at least to ∼350 ka, the oldest yet TL-dated such sequence in South Island. Furthermore...