| 1. |
- Dehnert, Andreas, et al.
(författare)
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Cosmogenic isotope burial dating of fluvial sediments from the Lower Rhine Embayment, Germany
- 2011
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Ingår i: Quaternary Geochronology. - 1871-1014 .- 1878-0350.
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Tidskriftsartikel (refereegranskat)abstract
- Cosmogenic isotope burial dating, using 10Be and 26Al, was applied to PlioePleistocene fluvial successionsfrom the Lower Rhine Embayment, Germany. The approach consists of three principal steps: (1)measurement of cosmogenic nuclides in depth profiles, (2) modelling of hypothetical nuclide concentrationsbased on a first-order conceptualisation of the geological context and the principal succession ofdepositions and subsequent erosional and burial phases, and (3) using parameter estimation to identifyvalues for the a priori unknown model parameters (burial age, initial nuclide concentrations, terraceerosion rates) that result in minimal disagreement between hypothetical and measured nuclideconcentrations.
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| 2. |
- Gennari, Giordana, et al.
(författare)
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Faunal evidence of a Holocene pluvial phase in Southern Arabia with remarks on the morphological variability of Helenina anderseni
- 2011
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Ingår i: Journal of Foraminiferal Research. - 0096-1191 .- 1943-264X. ; 41, s. 248-259
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Tidskriftsartikel (refereegranskat)abstract
- Although foraminifera have been found living in inlandsaline lakes isolated from the sea, this phenomenon has rarelybeen recognized in the fossil record. This study documents theoccurrence of benthic foraminifera in Holocene lake sedimentslocated nearly 500 km inland from the Red Sea, in theAl-Mundafan region of southern Saudi Arabia. The lakeformed during a regional pluvial period, 10,500–6000 yr BP.The presence of foraminifera and brackish charophytes in thestudied section represent an interval when the lake wasslightly brackish due to high evaporation. The studiedsediments yielded a bispecific benthic foraminiferal faunacomprised of Helenina anderseni and Trichohyalus aguayoi,as well as the brackish charophyte genus Lamprothamnium.The benthic foraminifera are species characteristic ofmangrove swamps, salt marshes, and lagoons, which areenvironments currently widespread along the Red Sea coasts.Because the Al Mundafan area was never connected to the seaduring the Quaternary, wading birds must have been thevector that transported the foraminifera to the paleolake
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| 3. |
- Juschus, Olaf, et al.
(författare)
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Late Quaternary Lake-Level Changes of Lake El´gygytgyn, NE Siberia
- 2011
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Ingår i: Quaternary Research. - 0033-5894 .- 1096-0287. ; 76, s. 411-451
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Tidskriftsartikel (refereegranskat)abstract
- Lake El'gygytgyn is situated in a 3.6 Ma old impact crater in northeastern Siberia. Presented here is areconstruction of the Quaternary lake-level history as derived from sediment cores from the southern lakeshelf. There, a cliff-like bench 10 m below the modern water level has been investigated. Deep-watersediments on the shelf indicate high lake levels during a warm Mid-Pleistocene period. One period with lowlake level prior to Marine Oxygen Isotope Stage (MIS) 3 has been identified, followed by a period of high lakelevel (10 m above present). In the course of MIS 2 the lake level dropped to −10 m. At the end of MIS 2 thebench was formed and coarse beach sedimentation occurred. Subsequently, the lake level rose rapidly to theHolocene level. Changes in water level are likely linked to climate variability. During relatively temperateperiods the lake becomes free of ice in summer. Strong wave actions transport sediment parallel to the coastand towards the outlet, where the material tends to accumulate, resulting in lake level rise. During coldperiods the perennial lake ice cover hampers any wave activity and pebble-transport, keeping the outlet openand causing the lake level to drop.
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| 4. |
- Lowick, Sally, et al.
(författare)
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Investigating age underestimation in the high dose region of optically stimulated luminescence using fine grain quartz
- 2011
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Ingår i: Quaternary Geochronology. - : Elsevier BV. - 1871-1014 .- 1878-0350. ; 6, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- The age range of the single-aliquot regenerative-dose (SAR) protocol applied to quartz optically stimulatedluminescence (OSL) has become the subject of debate as age underestimations for samples ofEemian age (ca. 125 ka) and older are increasingly reported. In order to investigate the origin of the ageunderestimation, the behaviour of fine grain quartz samples taken from two sites was compared.Sediment from both sites originates in the Alps, with those from Azzano Decimo, northeastern Italy,already displaying a significant age underestimation before reaching the Eemian, while ages for samplesfrom Niederweningen, northern Switzerland, agree with expected ages well beyond the Eemian. Estimateddose (De) values for both sets of samples are up to around 400 Gy, and all meet the usualperformance criteria for testing the reliability of the SAR protocol. De values determined using a sensitivity-corrected multiple aliquot regenerative-dose (MAR) protocol were within 10% of those determinedusing a SAR protocol for both sites, and so could not overcome the significant underestimation seen atAzzano Decimo. Lifetime calculations confirmed the stability of the signal well beyond the age rangerequired at both sites, for both the initial integral as well as that used for an early backgroundsubtraction. The relative percentage contribution of the fast and medium OSL components to the initialintegral remained constant in both the natural signal and similar sized laboratory generated doses. Thequartz OSL from both sites displayed similar characteristics under all analyses and no indication wasfound for the possible origin of the age underestimation seen at Azzano Decimo. In the comparisonsmade between the doseeresponse of both laboratory and naturally generated signals in these samples,no evidence was found to suggest that the presence of the high dose linear region is restricted to thelaboratory. The reliability of quartz OSL ages derived from this part of the curve however, remain inquestion, and require the support of independent age control until a performance criterion can be foundwith which to test it.
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| 5. |
- Lüthgens, Christopher, et al.
(författare)
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Age of the Pomeranian ice-marginal position in northeastern Germanydetermined by Optically Stimulated Luminescence (OSL) dating ofglaciofluvial sediments
- 2011
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Ingår i: Boreas. - 0300-9483 .- 1502-3885. ; 40, s. 598-615
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Tidskriftsartikel (refereegranskat)abstract
- The Pomeranian ice margin is one of the most prominent ice-marginal features of the Weichselian glaciation innorthern Europe. Previous results of surface-exposure dating (SED) of this ice margin disagree with establishedchronologies and ice retreat patterns, i.e. are much younger than previously expected. We crosscheck the age of thePomeranian ice-marginal position in northeastern Germany using single-grain quartz Optically Stimulated Luminescence(OSL) dating of glaciofluvial sediments. OSL dating indicates an active ice margin between 20.11.6 kaand 19.42.4 ka forming outwash plains attributed to the Pomeranian ice-marginal position. On the basis of theseresults, we suggest a critical reassessment of previous SED data available for the Pomeranian ice-marginal positionwithin their respective regional geomorphological contexts. From a process-based point of view, SED ages derivedfrom glacigenic boulders document the stabilization of the landscape after melting of dead ice and landscapetransformation under periglacial conditions rather than the presence of an ice margin. SED indicates a firstphase of boulder stabilization at around 16.40.7 ka, followed by landscape stabilization within the area attributedto the recessional Gerswalder subphase around 15.20.5 ka. A final phase of accumulation of glaciolacustrine andglaciofluvial sediments at around 14.71.0 ka documents the melting of buried dead ice at that time.
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| 6. |
- May, Jan-Henrik, et al.
(författare)
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Reconstruction of a complex late Quaternary glacial landscape in the Cordillera de Cochabamba (Bolivia) based on a morphostratigraphic and multiple dating approach.
- 2011
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Ingår i: Quaternary Research. - 0033-5894 .- 1096-0287. ; 76, s. 106-118
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Tidskriftsartikel (refereegranskat)abstract
- Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations inthe Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results fromdetailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulatedluminescence (OSL), and radiocarbon dating (14C) from the Huara Loma Valley, Cordillera de Cochabamba(Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solidgeomorphic framework. We identified two major glaciations. The older is not well constrained by theavailable data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regardingthe latter, a first advance dated to ~29–25 ka occurred roughly contemporaneous with the onset of the globallast glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20–18 ka. The locallast glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~17–16 ka,followed by several smaller readvances until ~10–11 ka, and complete deglaciation at the end of the EarlyHolocene.
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| 7. |
- Preusser, Frank, 1967-, et al.
(författare)
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Quaternary glaciation history of northern Switzerland
- 2011
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Ingår i: E&G Quaternary Science Journal. - 0424-7116. ; 60, s. 282-305
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Tidskriftsartikel (refereegranskat)abstract
- A revised glaciation history of the northern foreland of the Swiss Alps is presented by summarising field evidence and chronologicaldata for different key sites and regions. The oldest Quaternary sediments of Switzerland are multiphase gravels intercalated bytill and overbank deposits (‘Deckenschotter’). Important differences in the base level within the gravel deposits allows the distinguishingof two complex units (‘Höhere Deckenschotter’, ‘Tiefere Deckenschotter’), separated by a period of substantial incision.Mammal remains place the older unit (‘Höhere Deckenschotter’) into zone MN 17 (2.6–1.8 Ma). Each of the complexes containsevidence for at least two, but probably up-to four, individual glaciations. In summary, up-to eight Early Pleistocene glaciations ofthe Swiss alpine foreland are proposed. The Early Pleistocene ‘Deckenschotter’ are separated from Middle Pleistocene depositionby a time of important erosion, likely related to tectonic movements and/or re-direction of the Alpine Rhine (Middle PleistoceneReorganisation – MPR). The Middle-Late Pleistocene comprises four or five glaciations, named Möhlin, Habsburg, Hagenholz(uncertain, inadequately documented), Beringen, and Birrfeld after their key regions. The Möhlin Glaciation represents the mostextensive glaciation of the Swiss alpine foreland while the Beringen Glaciation had a slightly lesser extent. The last glacial cycle(Birrfeld Glaciation) probably comprises three independent glacial advances dated to ca. 105 ka, 65 ka, and 25 ka. For the last glacialadvance, a detailed radiocarbon chronology for ice build-up and meltdown is presented.
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| 8. |
- Rosenberg, Thomas M., et al.
(författare)
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A comparison of single and multiple aliquot TT-OSL data sets for sand-sized quartzfrom the Arabian Peninsula
- 2011
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Ingår i: Radiation Measurements. - : Elsevier BV. - 1350-4487 .- 1879-0925. ; 46:6-7, s. 573-579
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Tidskriftsartikel (refereegranskat)abstract
- The quartz OSL signal from dune sands from Saudi Arabia and Oman start to saturate at doses of about100 Gy. In order to try to date dune sands with greater expected doses, a previously published,single-aliquot, regenerative-dose protocol (SAR) for thermally-transferred optically stimulatedluminescence (TT-OSL) was tested. Dose recovery tests, recycling and recuperation ratios showed robustfunctioning and dose response curves demonstrated the potential to extend the dose range to beyond600 Gy. Multiple aliquot additive dose (MAAD) TT-OSL protocols were used to test for sensitivity changesin the SAR TT-OSL protocol up to doses of 1200 Gy. A strong dose dependent deviation of the SAR TT-OSLrelative to the MAAD TT-OSL dose response is observed. Comparison of the TT-OSL and OSL sensitivitydata obtained from the MAAD and SAR data sets shows a lack of proportionality between TT-OSL and OSLfor the SAR data which will result in a problem when SAR dose response curves are constructed usingmany regeneration points with doses above 300 Gy.
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| 9. |
- Vojtko, Ratislav, et al.
(författare)
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Late Quaternary fault activity in the Western Carpathians : evidence from the Vikartovce Fault (Slovakia)
- 2011
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Ingår i: Geologica Carpathica. - : Central Library of the Slovak Academy of Sciences. - 1335-0552 .- 1336-8052. ; 62:6, s. 563-574
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Tidskriftsartikel (refereegranskat)abstract
- The Cenozoic structure of the Western Carpathians is strongly controlled by faults. The E-W striking Vikartovcefault is one of the most distinctive dislocations in the region, evident by its geological structure and terrain morphology.This feature has been assumed to be a Quaternary reactivated fault according to many attributes such as its perfectlinearity, faceted slopes, the distribution of travertines along the fault, and also its apparent prominent influence on thedrainage network. The neotectonic character of the fault is documented herein by morphotectonic studies, longitudinaland transverse valley profile analyses, terrace system analysis, and mountain front sinuosity. Late Pleistocene activityof the Vikartovce fault is now proven by luminescence dating of fault-cut and uplifted alluvial sediments, presentlylocated on the crest of the tilted block. These sediments must slightly pre-date the age of river redirection. Consideringthe results of both luminescence dating and palynological analyses, the change of river course probably occurred duringthe final phase of the Riss Glaciation (135 ± 14 ka). The normal displacement along the fault during the Late Quaternaryhas been estimated to about 105—135 m, resulting in an average slip rate of at least 0.8—1.0 mm · yr—1. The present resultsidentify the Vikartovce fault as one of the youngest active faults in the Central Western Carpathians.
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