241Am dating of lake sediments

Appleby, P. G.; Richardson, N.; Nolan, P. J.

doi:10.1007/978-94-011-3592-4_4

Cited by 81 publications

(64 citation statements)

References 11 publications

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“…On the other hand, the 1986 Chernobyl fallout is used to date the most recent part of cores (Appleby 1991). A property of Cs is its high mobility in marine sediments, with a preferential downward diffusive transport in porewater (Radakovitch et al 1999).…”

Section: Resultsmentioning

confidence: 99%

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

et al. 2010

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ABSTRACT.To obtain a precise radiocarbon Holocene chronology in coastal areas, it is necessary to estimate the modern 14 C reservoir age R(t) and its possible variations with time in relation to paleoenvironmental changes. The modern reservoir 14 C age was estimated by comparing AMS 14 C ages of 2 recent mollusk shells found in sediment cores sampled in the Palavasian lagoonal system (south of France) with ages derived from 210 Pb and 137 Cs data and historical accounts of identifiable storm events. The calculated modern R(t) value of 943 ± 25 14 C yr is about 600 yr higher than the global mean sea surface reservoir age. This high value, probably due to the relative isolation of the lagoon from marine inputs, is in good agreement with other R(t) estimates in Mediterranean lagoonal systems (Zoppi et al. 2001;Sabatier et al. 2008). 14 C ages were also obtained on a series of Holocene mollusk shells sampled at different depths of the ~8-m-long core PB06. Careful examination of the 14 C ages versus depth relationships suggests that R(t) in the past was lower and similar to the value presently measured in the Gulf of Lion (618 ± 30 14 C yr, Siani et al. 2000). The change in R(t) from 618 to 943 yr is thought to result from final closure of the coastal lagoon by the sandy barrier, due to the along-shore sediment transfer.

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Section: Resultsmentioning

confidence: 99%

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

et al. 2010

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“…However, further pinning down the chronology using 137 Cs was impossible as the record revealed the constant occurrence of 137 Cs down to a sediment depth of 9 cm (Figure 4) without distinct peaks attributable to the maximum of thermonuclear weapon testing in 1963 or the Chernobyl reactor accident in 1986 (Appleby, 2001), likely owed to post-sedimentary diffusion of 137 Cs within the soft and water-saturated surface sediments (Davis et al, 1984;Klaminder et al, 2012). Instead, precise chronological information can be gained from 241 Am, which is less mobile than 137 Cs and has a longer half life, making activity peaks easier detectable (Appleby et al, 1991). Accordingly, the strong 241 Am activity increase at 5.5 cm can be likely attributed to the onset of atmospheric nuclear weapon testing in 1950 at the former USSR test site Semipalatinsk, ~1000 km north of Son Kol.…”

Section: Sediment Core Chronologymentioning

confidence: 99%

Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years

et al. 2014

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In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio)geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100–4350, 3450–2850, and 1900–1500 cal. yr BP. The distinct ~1500- year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia

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“…In the Southern Hemisphere, the maximum fall out peaks of fission products ( 137 Cs; 241 Pu, indirectly measured by 241 Am; and 90 Sr) are clearly associated with the most intensive testing activity between 1961 to 1962, leading in the southern South America to subsequently fallout with the highest fluxes in 1964 and 1965 [Arnaud et al, 2006;Magand and Arnaud, 2007]. 241 Am is used to corroborate 137 Cs dates in case of possible disturbance of the 137 Cs profile [Appleby et al, 1991;Oldfield et al, 1995;Pourchet et al, 2003;Eisen et al, 2008].…”

Section: Radionuclides Speciesmentioning

confidence: 99%

A promising location in Patagonia for paleoclimate and paleoenvironmental reconstructions revealed by a shallow firn core from Monte San Valentín (Northern Patagonia Icefield, Chile)

et al. 2008

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International audienceThe study of past climate variability from ice core investigations has been largely developed both in polar areas over the past decades and, more recently, in tropical regions, specifically along the South American Andes between 0° and 20°S. However a large gap still remains at mid-latitudes in the Southern Hemisphere. In this framework, a 15.3-m long shallow firn core has been extracted in March 2005 from the summit plateau of Monte San Valentín (3747 m, 46°35′S, 73°19′W) in the Northern Patagonia Icefield to test its potential for paleoclimate and paleoenvironmental reconstructions. The firn temperature is −11.9°C at 10-m depth allowing to expect well preserved both chemical and isotopic signals, unperturbed by water percolation. The dating of the core, on the basis of a multi-proxy approach combining annual layer counting and radionuclide measurements, shows that past environment and climate can be reconstructed back to the mid-1960s. A mean annual snow accumulation rate of 36 ± 3 cm year−1 (i.e., 19 ± 2 g cm−2 year−1) is inferred, with a snow density varying between 0.35 and 0.6 g cm−3, which is much lower than accumulation rates previously reported in Patagonia at lower elevations. Here, we present and discuss high-resolution profiles of the isotopic composition of the snow and selected chemical markers. These data provide original information on environmental conditions prevailing over Southern Patagonia in terms of air masses trajectories and origins and biogeochemical reservoirs. Our main conclusion is that the San Valentín site is not only influenced by air masses originating from the southern Pacific and directly transported by the prevailing west winds but also by inputs from South American continental sources from the E–NE, sometimes mixed with circumpolar aged air masses, the relative influence of these two very distinct source areas changing at the interannual timescale. Thus this site should offer a wealth of information regarding (South) Pacific, Argentinian NE–E areas and Antarctic climate variability

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241Am dating of lake sediments

Cited by 81 publications

References 11 publications

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years

A promising location in Patagonia for paleoclimate and paleoenvironmental reconstructions revealed by a shallow firn core from Monte San Valentín (Northern Patagonia Icefield, Chile)

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