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  • Cambridge University Press
  • 2010-2014  (10,840)
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  • 1
    Publication Date: 2013-09-25
    Description: Publication date: Available online 24 September 2013 Source: Quaternary Research Author(s): Daniel E. Karig , Norton G. Miller Areal mapping of the middle Wisconsin varved clay site along Sixmile Creek near Ithaca, New York, has revealed a much more widespread and varied array of sediments than previously thought. Lacustrine clays, some varved, are interbedded with sands and gravels interpreted as sub-aqueous fan deposits, and both are overlain by a deformation till. Nine radiocarbon dates indicate a 34–37 14 C ka BP age for the lacustrine sediment, with the deformation till less than a few thousand years younger. Beneath this sequence is a deposit dated at ± 42 14 C ka BP. Both strata represent a tundra climate with a mean July temperature of about 10°C. The Sixmile Creek deformation till must correlate with the 35 14 C ka BP till along the Genesee River, 125 km to the NW, and defines a Cherrytree stade glacial advance into the Appalachian Plateau, much further south than what has generally been accepted. Such an advance would require drainage from a proglacial lake in the western Ontario basin to flow westward instead of northeastward. The Sixmile strata suggest a colder than accepted middle Wisconsin stage. Recent data indicate that this stage is one of progressive cooling, with large climatic fluctuations.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
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  • 2
    Publication Date: 2013-09-26
    Description: Publication date: Available online 25 September 2013 Source: Quaternary Research Author(s): Denis Geraads , Fethi Amani , Abdelouahed Ben-Ncer , Shannon P. McPherron , Jean-Paul Raynal , Jean-Jacques Hublin The rodents from the late middle Pleistocene hominin-bearing locality of J'bel Irhoud include the following species: Meriones shawii , Gerbillus grandis , Dipodillus campestris , Paraethomys ras , Lemniscomys barbarus , Mus cf. spretus , and Eliomys sp. We consider M. shawii , a living species, as identical with the middle Pleistocene Meriones maghrebianus . The mouse differs from the domestic Mus musculus but does not clearly fit into Mus spretus , either. The rare G. grandis looks identical with the form from the middle Pleistocene of Thomas quarries, which may suggest a rather early age for Irhoud. This is in agreement with the occurrence of Paraethomys , a genus unknown in the upper Pleistocene of Morocco, but the absence of the arvicolid Ellobius suggests that the site is younger than other middle Pleistocene sites, Doukkala II, Sidi Abderrahmane D2, and Irhoud-Derbala-Virage. Paleoecological indicators, such as the taxonomic habitat spectrum, or the relative abundances of Gerbillinae and Murinae, suggest a less xeric environment than in many earlier and later sites. Diversity indices, comparable to those of other middle Pleistocene sites, point to similarly favorable conditions before the major climatic crisis close to the middle/upper Pleistocene boundary that drastically reduced rodent diversity in North Africa.
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  • 3
    Publication Date: 2013-09-26
    Description: Publication date: Available online 25 September 2013 Source: Quaternary Research Author(s): Mikael Ohlson , Isabella Kasin , Anveig Nordtug Wist , Anne E. Bjune Forest fires convert a proportion of the burning vegetation into charcoal that is stored in forest soils and lake sediments. In this paper we use a geostatistical approach to present a detailed analysis of the size of the charcoal pool and its spatial variation in a boreal forest watershed including its lake sediment. The amount of soil charcoal averaged 179 g/m 2 and ranged from 0 to 3600 g/m 2 in the watershed. There was an extreme variation in the size of the charcoal pool over fine (cm) spatial scales. For example, the amount of charcoal in the soil could range from 34 to 1646 g/m 2 within a distance of 10 cm. Individually dated soil charcoal particles had radiocarbon ages that varied from 630 to 2930 cal yr BP. The lake sediment began accumulating at 10,600 cal yr BP and charcoal accumulation has been practically continuous ever since then, with the largest peak occurring at 6900 cal yr BP. The lake sediment contained more charcoal, 360 g/m 2 , than the average for forest soil. We interpret this as an indication of a relatively rapid degradation of charcoal in boreal forest soils.
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  • 4
    Publication Date: 2013-09-30
    Description: Publication date: Available online 29 September 2013 Source: Quaternary Research Author(s): Julien Carcaillet , Isandra Angel , Eduardo Carrillo , Franck A. Audemard , Christian Beck In the tropical Mérida Andes (northwestern Venezuela), glacial landforms were found at altitudes between 2600 and 5000 m, corresponding to 600 km 2 of ice cover during the maximum glacial extension. However, the lack of sufficient absolute age data prevents detailed reconstruction of the timing of the last deglaciation. On the northwestern flank of the Mucuñuque Massif, successive moraines and striated eroded basement surfaces were sampled for cosmogenic 10 Be investigation. Their compilation with published data allows the establishment of a detailed chronology of the post-LGM glacier history. The oldest moraines (18.1 and 16.8 ka) correspond to the Oldest Dryas. Successive moraine ridges indicate stops in the overall retreat between the LGM and the Younger Dryas. The cold and short Older Dryas stadial has been identified. Results indicate that most of the ice withdrew during the Pleistocene. The dataset supports an intensification of the vertical retreat rate from ~ 25 m/ka during the late Pleistocene to ~ 310 m/ka during the Pleistocene/Holocene. Afterwards, the glacier was confined and located in the higher altitude zones. The altitude difference of the Younger Dryas moraines in the Mucubají, La Victoria and Los Zerpa valleys indicates a strong effect of valley orientation on the altitude of moraine development.
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  • 5
    Publication Date: 2013-10-04
    Description: Publication date: Available online 3 October 2013 Source: Quaternary Research Author(s): Nicole E. Spaulding , John A. Higgins , Andrei V. Kurbatov , Michael L. Bender , Steven A. Arcone , Seth Campbell , Nelia W. Dunbar , Laura M. Chimiak , Douglas S. Introne , Paul A. Mayewski Terrestrial meteorite ages indicate that some ice at the Allan Hills blue ice area (AH BIA) may be as old as 2.2 Ma. As such, ice from the AH BIA could potentially be used to extend the ice core record of paleoclimate beyond 800 ka. We collected samples from 5 to 10 cm depth along a 5 km transect through the main icefield and drilled a 225 m ice core (S27) at the midpoint of the transect to develop the climate archive of the AH BIA. Stable water isotope measurements (δD) of the surface chips and of ice core S27 yield comparable signals, indicating that the climate record has not been significantly altered in the surface ice. Measurements of 40 Ar atm and δ 18 O atm taken from ice core S27 and eight additional shallow ice cores constrain the age of the ice to approximately 90–250 ka. Our findings provide a framework around which future investigations of potentially older ice in the AH BIA could be based.
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  • 6
    Publication Date: 2013-10-04
    Description: Publication date: Available online 3 October 2013 Source: Quaternary Research Author(s): Yurena Yanes , María P. Asta , Miguel Ibáñez , María R. Alonso , Christopher S. Romanek Land snail shell δ 13 C value is often used as a paleovegetation proxy assuming that snails ingest all plants in relation to their abundance, and that plants are the only source of carbon. However, carbonate ingestion and variable metabolic rates complicate these relationships. We evaluate if live-collected snails from Lanzarote (Canary Islands) reflect the abundance of C 3 and CAM plants. Snails were collected on either CAM or C 3 plants for isotope analysis of shell and body, and shell size. Respective shell and body δ 13 C values of snails collected on CAM plants averaged − 8.5 ± 1.7‰ and − 22.8 ± 1.6‰, whereas specimens from C 3 plants averaged − 10.1 ± 0.7‰ and − 24.9 ± 1.1‰. A flux balance model suggests snails experienced comparable metabolic rates. A two-source mass balance equation implies that snails consumed ~ 10% of CAM, which agrees with their abundance in the landscape. Snails collected on CAM plant were smaller than those on C 3 plants. Conclusively: 1) snails consume CAM plants when they are available; 2) migration of snails among C 3 and CAM plants is a common phenomenon; and 3) C 3 plants may be a more energetic food for growth than CAM plants. This study shows that shell δ 13 C values offer approximate estimates of plants in C 3 –CAM mixed environments.
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  • 7
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    Cambridge University Press
    Publication Date: 2013-06-08
    Description: Publication date: Available online 7 June 2013 Source: Quaternary Research Author(s): William R. Dickinson Unlike most tropical Pacific islands, which lie along island arcs or hotspot chains, the Loyalty Islands between New Caledonia and Vanuatu owe their existence and morphology to the uplift of pre-existing atolls on the flexural forebulge of the New Hebrides Trench. The configuration and topography of each island is a function of distance from the crest of the uplifted forebulge. Both Maré and Lifou are fully emergent paleoatolls upon which ancient barrier reefs form highstanding annular ridges that enclose interior plateaus representing paleolagoon floors, whereas the partially emergent Ouvea paleoatoll rim flanks a drowned remnant lagoon. Emergent paleoshoreline features exposed by island uplift include paleoreef flats constructed as ancient fringing reefs built to past low tide levels and emergent tidal notches incised at past high tide levels. Present paleoshoreline elevations record uplift rates of the islands since last-interglacial and mid-Holocene highstands in global and regional sea levels, respectively, and paleoreef stratigraphy reflects net Quaternary island emergence. The empirical uplift rates vary in harmony with theoretical uplift rates inferred from the different positions of the islands in transit across the trench forebulge at the trench subduction rate. The Loyalty Islands provide a case study of island environments controlled primarily by neotectonics.
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  • 8
    Publication Date: 2013-06-08
    Description: Publication date: Available online 7 June 2013 Source: Quaternary Research Author(s): Thomas R. Lakeman , John H. England The study revises the maximum extent of the northwest Laurentide Ice Sheet (LIS) in the western Canadian Arctic Archipelago (CAA) during the last glaciation and documents subsequent ice sheet retreat and glacioisostatic adjustments across western Banks Island. New geomorphological mapping and maximum-limiting radiocarbon ages indicate that the northwest LIS inundated western Banks Island after ~ 31 14 C ka BP and reached a terminal ice margin west of the present coastline. The onset of deglaciation and the age of the marine limit (22–40 m asl) are unresolved. Ice sheet retreat across western Banks Island was characterized by the withdrawal of a thin, cold-based ice margin that reached the central interior of the island by ~ 14 cal ka BP. The elevation of the marine limit is greater than previously recognized and consistent with greater glacioisostatic crustal unloading by a more expansive LIS. These results complement emerging bathymetric observations from the Arctic Ocean, which indicate glacial erosion during the Last Glacial Maximum (LGM) to depths of up to 450 m.
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  • 9
    Publication Date: 2013-04-11
    Description: Publication date: Available online 10 April 2013 Source: Quaternary Research The distribution of marine-influenced oxygen isotope stage (OIS) 5 to OIS 1 sediments was examined in several late Quaternary boreholes from the southern Changjiang (Yangtze) delta plain, China, using different dating methods including OSL, U-series, AMS 14 C and paleomagnetism. Results demonstrate that coastal and estuarine deposition during OIS 5 and OIS 3 occurred throughout the study area. However, Holocene transgressive sediments were absent on the Taihu block. The burial depth of intertidal to subtidal sediment deposited during OIS 5e records 30–80 m subsidence caused by sediment compaction and tectonic movement since that time. However, coastal sediments formed during the late phase of OIS 3 were buried to a depth of ca. 6–15 m in the Taihu Lake area, while the burial depth increased eastward to ca. 45–60 m on the coastal plain. This phenomenon, combined with the distribution of Holocene marine strata, indicates at least 25–30 m uplift of the Taihu block since the end of OIS 3. We suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post-glacial deposition by the Changjiang and Huanghe Rivers on the continental shelf of east China marginal sea.
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  • 10
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    Cambridge University Press
    Publication Date: 2013-09-06
    Description: Publication date: Available online 5 September 2013 Source: Quaternary Research Author(s): Vachel A. Carter , Andrea Brunelle , Thomas A. Minckley , Philip E. Dennison , Mitchell J. Power Fire is one of the most important natural disturbances in the coniferous forests of the US Rocky Mountains. The Rocky Mountains are separated by a climatic boundary between 40° and 45° N, which we refer to as the central Rocky Mountains (CRM). To determine whether the fire regime from the CRM was more similar to the northern Rocky Mountains (NRM) or southern Rocky Mountains (SRM) during the Holocene, a 12,539-yr-old sediment core from Long Lake, Wyoming, located in the CRM was analyzed for charcoal and pollen. These data were then compared to charcoal records from the CRM, NRM and SRM. During the Younger Dryas chronozone, the fire regime was characterized as frequent at Long Lake. The early and middle Holocene fire regime was characterized as infrequent. A brief interval from 4000 to 3000 cal yr BP, termed the Populus period, had a frequent fire regime and remained frequent through the late Holocene at Long Lake. In comparison to sites from the NRM and SRM, the fire regime at Long Lake was most similar to the SRM during the past 12,539 cal yr BP. These results suggest the disturbance regime in the CRM has a greater affinity with those of the SRM.
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