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1.
Radiat Prot Dosimetry ; 186(1): 94-112, 2019 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-31840174

RESUMO

ESR (electron spin resonance) can date sites that span the whole Paleolithic, but requires accurate sedimentary dose rates, especially in caves where the internal and cosmic dose rates can approach 0 mGy/yr. This study examines the sedimentary radioactivity in the upper layers at Golema Pest, North Macedonia. Reaching > 5.5 m deep, > 21 flatly lying, silty-sandy matrix-supported gravel layers with éboulis clasts fill the cave. In Sondage 2, Layers 0-5 contained many hearths and yielded thousands of bones and teeth, many from ungulates. In Layers 2-5a sat thousands of lithics and small tools, many made on tiny quartz crystals. Layers 2c-6 have Mousterian assemblages with denticulates, notched tools, Levallois cores and flakes. To measure the volumetrically averaged sedimentary dose rates for ungulate teeth dated by ESR from Sondage 2, 66 sediment samples were analyzed by NAA. Adding éboulis, calcined bone, and charcoal associated with the hearths lowered the sedimentary dose rates or left them unchanged. In Layer 2 at 198 cm below the cave datum, the Campanian Ignimbrite (CI) cryptotephra occurred, where it caused abnormally high sedimentary U, Th, and K concentrations and dose rates. Since the CI tephra lay 28-30 cm above AT77, a tooth dated from Layer 3, using time- and volumetrically averaging increased AT77's sedimentary dose rate by 32%, and dropped its calculated age by 25%. Analyzing the sedimentary compositions at every 2 cm in Layers 0-2 yielded a highly detailed stratigraphy that reduced the uncertainty in the sedimentary dose rates and the ESR ages, but more detailed geochemical analyses must be completed within the lower layers in Sondage 2.


Assuntos
Esmalte Dentário/efeitos da radiação , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Sedimentos Geológicos/análise , Paleontologia/métodos , Monitoramento de Radiação/métodos , Datação Radiométrica/métodos , Animais , Osso e Ossos , Cavernas , Fósseis , Grécia , Humanos , Mamíferos , Doses de Radiação
2.
Radiat Prot Dosimetry ; 159(1-4): 220-32, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24943512

RESUMO

Near Hatay, the Antakya-Samandag-Cyprus Fault (ASCF), East Anatolian and Dead Sea Fault Zones, the large faults that form the edges of the African, Anatolian, Cyprus and Arabian Plates, all produce large earthquakes, which have decimated Hatay repeatedly. Near Samandag, Hatay, differential vertical displacement on the ASCF has uplifted the southeastern side relative to northwestern side, producing large fault scarps that parallel the Asi (Orontes) River. Tectonic uplift coupled with Quaternary sealevel fluctuations has produced several stacked marine terraces stranded above current sealevel. This study dated 24 mollusc samples from 10 outcrops on six marine terraces near Samandag electron spin resonance (ESR). Ages were calculated using time-averaged and volumetrically averaged external dose rates, modelled by assuming typical water depths for the individual species and sediment thicknesses estimated from geological criteria. Uplift rates were then calculated for each fault block. At all the Magaracik terraces, the dates suggest that many shells were likely reworked. On the 30 m terrace at Magaracik IV (UTM 766588-3999880), Lithophagus burrows with in situ shells cross the unconformity. One such shell dated to 62 ± 6 ka, setting the minimum possible age for the terrace. For all the Magaracik terraces at ∼30 m above mean sealevel (amsl), the youngest ages for the reworked shells, which averaged 60 ± 3 ka for six separate analyses, sets the maximum possible age for this unit. Thus, the terrace must date to 60-62 ± 3 ka, at the MIS 3/4 boundary when temperatures and sealevels were fluctuating rapidly. Older units dating to MIS 7, 6, and 5 likely were being eroded to supply some fossils found in this terrace. At Magaracik Dump (UTM 765391-4001048), ∼103 m amsl, Ostrea and other shells were found cemented in growth position to the limestone boulders outcropping there <2.0 m above a wave-eroded notch. If the oysters grew at the same time as the wave-cut notch and the related terrace, the date, 91 ± 13 ka, for the oysters, this fault block has been uplifted at 1.19 ± 0.15 m ky(-1), since MIS 5c. At Samandag Kurt Stream at 38 m amsl, molluscs were deposited fine sandy gravel, which was likely formed in a large tidal channel. Four molluscs averaged 116 ± 5 ka. If these molluscs have not been reworked, this fault block has uplifted at 0.34 ± 0.05 m ky(-1) since the MIS 5d/5e boundary. The differences in these uplift rates suggests that at least one, and possibly two, hitherto undiscovered faults may separate the Magaracik Dump site from the other Magaracik sites and from the Samandag Kurt Stream site.


Assuntos
Evolução Biológica , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Meio Ambiente , Fósseis , Sedimentos Geológicos/química , Paleontologia , Datação Radiométrica/métodos , Animais , Doses de Radiação , Turquia
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