Description: Publication year: 2012 Source: Quaternary Geochronology, Volume 7, February 2012, Pages 4-5 Nick Lancaster

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 20 November 2011 Lovisa Zillén, Conny Lenz, Tom Jilbert The prehistory of the Baltic Sea has for a long time suffered from imprecise dating, due to the large uncertainties associated with bulk radiocarbon dating of Baltic Sea sediments. To constrain the timing of environmental changes in the Baltic Sea it is thus critical to apply new dating approaches. This study identifies lead pollution isochrones in Baltic Sea sediments, which have previously been recorded in lake-sediment and peat deposits in northern Europe and ice cores from Greenland. These isochrones have formed through the deposition of atmospheric lead associated with historic lead production and silver mining in Europe, and more recently with the increased industrial emissions that peaked in the 1970’s. Lead concentration and stable lead isotope analyses (Pb/Pb ratios) reveal three distinct lead-pollution horizons in the Baltic Sea, i.e. a Roman peak at 1 AD, a Medieval peak at 1200 AD and a peak in the 1970s. The new data will improve the chronological accuracy and precision of paleoenvironmental studies in the Baltic Sea, and for the first time, allow synchronization of Baltic Sea geological records within the basin and across Europe and the North Atlantic region (including Greenland). Highlights .▶ Three Pb-isochrones have been identified in the Baltic Sea. ▶ These occurred at 1 AD, 1200 AD and in the 1970s. ▶ Pb-isochrones will improve the chronological control in the Baltic Sea

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 31 October 2011 Lewis G. Collins, Mark W. Hounslow, Claire S. Allen, Dominic A. Hodgson, Jennifer Pike, ... Establishing accurate chronologies for Late Quaternary Antarctic marine sediments is often a challenge due to variable radiocarbon reservoir effects, the presence of coarse-grained glacial material and a lack of carbonate preservation. Without accurate age control the scope for precise comparison of palaeoenvironmental records is severely limited. In order to address this, we combined diatom abundance stratigraphy, magnetic and radiocarbon methods to build an accurate chronology for two late glacial marine sedimentary sequences, from cores TPC063 and TPC286 from the Scotia Sea, SW Atlantic. Palaeomagnetic data provide the first evidence for the Laschamp geomagnetic excursion (∼41 cal ka B.P.) in Antarctic marine sediments and a relative palaeointensity curve that is tuned to the independently dated SAPIS relative palaeointensity reference stack. Together, these key findings provide an accurate age model between 43.7 cal ka B.P. and 25.3 cal ka B.P. The age model was further extended to 17.3 cal ka B.P. through identification of the diatomEucampia antarctica2Ea1abundance stratigraphy datum. Radiocarbon dating did not provide dates that were in stratigraphic order, and magnetic susceptibility only identified glacial interglacial transitions in one core. We demonstrate that combining geomagnetic and diatom abundance data can enable generation of high-resolution geochronologies for glacial sediments from the Scotia Sea, and offers the potential for more widespread comparison and correlation of Antarctic and Southern Ocean palaeoenvironmental records. Highlights. ► We generate a novel, high-resolution geochronology for difficult-to-date glacial Antarctic marine sediments. ► Palaeomagnetic data provide the first evidence for the Laschamp geomagnetic excursion in Antarctic marine sediments. ► We provide a means to accurately compare the climate archives of the glacial Southern Ocean with well-dated climate records.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 28 November 2011 Hao Long, ZhongPing Lai, Peter Frenzel, Markus Fuchs, Torsten Haberzettl Palaeolimnological studies together with geomorphological investigations of exposed lacustrine sections on the Tibetan Plateau provided valuable palaeoclimate records. Radiocarbon dating is the most commonly used method for establishing chronologies of lake sediments. However,C dating of such sediments could be problematic due to the lack of organic matter or a reservoir effect, which commonly appears in radiocarbon ages of lacustrine sediments from the Tibetan Plateau. OSL dating is an alternative for dating the lake sediments and also provides the opportunity to independently test radiocarbon chronologies. The current study tries to compare OSL andC dating results in order to evaluate the reservoir effect ofC dating, and then based on quartz OSL dating and stratigraphic analysis, to construct the chronostratigraphy of a lacustrine sedimentary sequence (TYC section), an offshore profile from Tangra Yumco lake on the southern Tibetan Plateau. Results suggest that: (1) it is possible to obtain robust OSL age estimates for these lake sediments and the OSL ages of the three samples range from ca. 7.6 ka to ca. 1.9 ka; (2) The discrepancy between the OSL andC ages is ca. 4-5 ka, which possibly results from the age overestimate ofC dating due to a reservoir effect in the studied lake; (3) the chronostratigraphy of TYC section and sedimentological environmental analysis show a large lake with a lake level distinctively above the present during ca. 7.6-2.3 ka indicating a wet mid-Holocene in the study area. Highlights ► we compared the OSL andC chronology of a lake profile on the Tibetan Plateau. ► TheC ages are ca. 4-5 ka older than the OSL ages. ► The age overestimate ofC dating is due to the reservoir effect in the study area. ► The chronostratigraphy of this lake profile indicates a large lake during 7.6-2.3 ka. ► This study suggests a wet mid-Holocene in the study area.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 1 December 2011 J.K. Feathers Anthropogenic rock alignments, both circular and linear, are common in the northern Rockies and adjacent High Plains of North America. Their ages are largely unknown. Luminescence dating of single-grain feldspars is applied to sediment under the rocks on the assumption that prior to rock placement turbation processes zeroed sufficient number of grains and that these processes ended with the rock placement. Ages of single grains are corrected for anomalous fading and the age of placement is estimated using the minimum age model. Vertical distributions of ages show that youngest ages are clustered just under the rock, conforming to the turbation model. Low precision in fading corrections led to attempts to reduce fading with higher temperature stimulations. These did reduce fading but also recovered known doses poorly, suggesting possible age over-estimation. This uncertainty coupled with a problem of small sample sizes from material with generally low sensitivity resulted in overall low precision in ages, but still an improvement over the current lack of chronological information. Highlights ► IRSL dating is applied to sediments under anthropogenic rock features. ► Minimum age model provides date of placement because of turbation. ► Problems with sample size and optimal stimulation temperature are encountered. ► Ages are provided for five localities, although precision is low.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 3 December 2011 Naomi Porat, Geoff A.T. Duller, Helen M. Roberts, Eliezer Piasetzky, Israel Finkelstein Megiddo, one of the most important mounds (Tel) in the Levant, was inhabited almost continuously from the 7millennium to the 4C. BC and archaeological remains have accumulated to a height of ca. 20 m. Megiddo features a significant number of destruction levels, some of which can be correlated to well-known historical events. Other destruction levels are less well dated, and in order to improve the chronological control, an OSL dating campaign was designed, particularly for those periods where the radiocarbon calibration curve incorporates large errors on radiocarbon dates.Twenty-six samples were collected from a range of archaeological periods, excavation areas and sediment types. In-situ gamma and cosmic dose rates were obtained either with Al2O3:C dosimeters that were buried at the site for 2 months or with a calibrated gamma scintillator. Very-fine-sand quartz was extracted and measured using conventional SAR to obtain the equivalent dose (De).The OSL age of many samples is older than the expected archaeological age and their Devalues are usually scattered. This suggests that sediments were continuously reused and recycled at Tel Megiddo without exposure to sunlight and very little fresh sediment was added directly from dust to the archaeological accumulation, challenging the basic requirement for OSL dating.Using combined criteria of sequential stratigraphic order of the samples and the over-dispersion of the measured Devalues helped to reject the samples that yield ages which fail to represent the age of their archeological context. Twelve of the 26 OSL ages had to be rejected, but the 14 ages which did pass the criteria agree very well with the expected archaeological ages. Thus analysis of a single sample is ineffective for determining an archeological age for a given context. Sediments from in-between building stones are more suitable than those taken from floors, streets and ash layers; samples from destruction layers should be avoided. Megiddo provides an example of the difficulties in OSL dating in a multi-period, complex archaeological site. Highlights ► 26 samples from Tel Megiddo were dated by OSL. ► 14 samples agree with expected archaeological age, the remaining are over-estimated. ► Sequential stratigraphic ordering allows to remove discordant samples. ► Low D e over-dispersion value is a good predictor for age agreement. ► Through the periods sediments were constantly recycled in the Tel.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 28 November 2011 Antoine J.C. Zink, George J. Susino, Elisa Porto, Thomas N. Huffman A pilot study used eleven excavated sites in the Limpopo Province of South Africa to test the application of OSL dating for Iron Age ceramic shards. The culture-history sequences of Iron Age is well established by pottery style and the sites had already been radiocarbon dated. Because the excavations were part of various research projects, rather than a specific OSL study, the sites have been destroyed and hence, local environmental radioactivity was unknown. To reconstruct the environmental dose rate, we used data from three sources: (1), a worldwide survey, (2), radionuclides in the pottery and (3) recent geological surveys. The geological surveys yielded the most dates that are reasonably close to the known chronology, reproducing the correct chronological order in most cases. Some dates, however, are 200 years too recent and some standard deviations too high. To evaluate further the potential of OSL dating in Iron Age research, dosimetry data need to be collectedin situ. Highlights ► We begin luminescence dating on Iron Age pottery from South Africa. ► Several sites dated by radiocarbon was selected. ► They have been destroyed and then the environmental dosimetry cannot be measured. ► Hypotheses based on regional geology yielded ages close to the known chronology.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 28 November 2011 M. Fuchs, S. Kreutzer, M. Fischer, D. Sauer, R. Sørensen Raised beach sand deposits along the southeastern coast of Norway were dated by optical (OSL) and infrared stimulated luminescence (IRSL) and the quartz and K-feldspar luminescence characteristics were described. Due to the poor quartz luminescence characteristics, only a limited number of samples were suitable for OSL dating. More promising are the K-feldspar extracts, with typical K-feldspar luminescence characteristics and no sign of fading. For equivalent dose (De) determination, sand-size quartz and feldspar extracts were used, applying a single aliquot regenerative (SAR) protocol. Both, OSL and IRSLDeestimates show a wide distribution, unexpected for beach deposits. The calculated OSL and IRSL age estimates were generally in good agreement and the correctness of the ages was confirmed by independent age control. Because only a limited number of the quartz samples were suitable for OSL dating, IRSL dating of the K-feldspar represents an alternative to OSL quartz dating. Highlights ► Beach sand deposits along the southeastern coast of Norway were dated by OSL and IRSL. ► TL, OSL, LM were applied to described luminescence characteristics. ► Quartz shows poor luminescence characteristics and only a limited number of quartz samples were dateable. ► IRSL shows no fading and represent an alternative to OSL dating.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 28 November 2011 Sven Lukas, Frank Preusser, Flavio S. Anselmetti, Willy Tinner The potential of luminescence dating of high-alpine lacustrine sediments is tested on samples taken from three high-altitude moraine-bounded lakes in the Swiss Alps. Independent age control is provided by radiocarbon ages and detailed palynological data in all cases. All samples show good luminescence characteristics (no thermal transfer, good dose recovery and recycling), but two samples show rather low quartz signals. Radioactive disequilibria in the uranium decay chain observed in one sample are accounted for by using a dynamic modelling approach. Because all cores had largely dried out and water content had not been measured after sampling, we developed a modern limnological approach to retrospectively establish palaeo-water content. Applying average water content values from a dataset of modern sediments with similar characteristics to the samples investigated here we obtained ages that match the independent age control. Whereas the low-signal quartz separates consistently underestimate these ages, the polymineral samples more accurately match them, do not suffer from anomalous fading and are thus considered reliable. This study demonstrates for the first time that applying luminescence dating to high-alpine, ice-proximal lacustrine sediments is a promising avenue to obtain a chronology for such depositional environments. Highlights ► Establishing water content is a key issue in Luminescence dating of subaqueous sediments. ► We have developed a method to do this for dried-up samples. ► We apply this method to proximal glaciolacustrine sediments. ► Feldspar ages match, while quartz underestimates, independent age control. ► Fine-grain dating is a promising avenue of dating proximal glaciolacustrine sediments.

Description: Publication year: 2011 Source: Quaternary Geochronology, Available online 28 November 2011 Norbert Mercier, Jean-Loïc Le Quellec, Malika Hachid, Safia Agsous, Michel Grenet The Tassili-n-Ajjer plateau is famous for its tens of thousands of pictographs discovered in the mid-XXcentury. Despite extensive studies aimed at preserving this art inscribed on the World Heritage List, the antiquity of these paintings remains hotly debated. Because recent attempts at dating with radiocarbon failed to provide reliable results, an OSL dating study focused on Quaternary deposits preserved at the feet of painted walls and which can be connected to them was undertaken. Thirteen sediment samples were collected from below and above the palaeosol where the painters might have lived. The OSL results indicate that the paintings are younger than ∼9-10 ka, but unfortunately they do not allow us to narrow the time interval during which they were made. Highlights ► The Tassili-n-Ajjer plateau is famous for its tens of thousands of pictographs. ► The antiquity of these paintings remains hotly debated. ► OSL dating results were obtained on 13 sediment samples. ► The ages indicate that the paintings are younger than ∼10 ka.