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  • 1
    Monographie ausleihbar
    Monographie ausleihbar
    Oxford [u.a.] : Oxford Univ. Pr.
    Signatur: 9/M 03.0331
    Materialart: Monographie ausleihbar
    Seiten: xxiii, 500 S.
    ISBN: 0195133536
    Klassifikation:
    Historische Geologie
    Standort: Lesesaal
    Zweigbibliothek: GFZ Bibliothek
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2023-10-11
    Beschreibung: We provide stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope measurements in individual calcitic valves of extant ostracode species, Sclerocypris clavularis, from modern sediments in 17 sites across Lake Turkana, eastern Africa. These sediments were collected using a modified Ekman dredge during May-November, 1979. Pooled statistics of these individual ostracode valve analyses (IOVA) of δ¹³C and δ¹⁸O measurements (n = 329) at each site show strong correlations with lake hydrological parameters. Within-site variance in IOVA-δ¹³C is larger (~60%) than that of IOVA-δ¹⁸O. Yet, pooled averages exhibit a systematic pattern with higher δ values towards the southern part of the lake, away from Omo River inflow, which is the largest riverine input into Lake Turkana (comprising ~90% of overall inflows). We suggest that the latitudinal δ¹³C gradient may arise from low riverine δ¹³C and low organic matter δ¹³C as a productivity response to nutrient-rich Omo River inflow towards the north. The δ¹⁸O pattern may be explained by the diminishing influence of Omo River inflows and more evaporation driving higher IOVA-δ¹⁸O values towards the windier, southern basin. We conclude that pooled IOVA statistics in Omo-Turkana sediments can aid interpretations of past regional paleohydrology and its variability in this basin.
    Schlagwort(e): lake sediments; ostracodes; oxygen and carbon isotopes
    Materialart: Dataset
    Format: application/zip, 2 datasets
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2023-10-11
    Beschreibung: This dataset contains measurements of individual ostracode valve analyses (IOVA), including stable oxygen (δ¹⁸O) and carbon (δ¹³C) isotopes, and length/width, and mass measurements, at 17 sites across Lake Turkana, eastern Africa. These sediments were collected using a modified Ekman dredge during May–November 1979. The stable isotopic measurements were conducted at the [Paleo² Laboratory at the University of Arizona|https://thirumalai.geo.arizona.edu/] on a Thermo Kiel IV Carbonate Device coupled to a 253 Plus IRMS; the length/width measurements were performed on a MeijiTechno HDZ7000TS Digital Zoom Microscope System, and mass of each valve was measured using a Sartorius Cubis II Ultra-Micro Balance. Details can be found in https://doi.org/10.1029/2022GC010790
    Schlagwort(e): 79-130F; 79-147F; 79-158F; 79-160F; 79-164F; 79-166F; 79-168F; 79-170F; 79-183F; 79-189F; 79-193F; 79-194F; 79-204F; 79-77F; BS125; BS90; BS91; Digital Zoom Microscope System, MeijiTechno, HDZ7000TS; EG; Ekman grab; Elevation of event; Event label; Hole; lake sediments; Lake Turkana, Africa; Latitude of event; Longitude of event; Mass spectrometer ThermoFisher Scientific 253plus gas coupled to a KIEL IV carbonate preparation device; Ostracoda, length; Ostracoda, mass; Ostracoda, δ13C; Ostracoda, δ18O; ostracodes; oxygen and carbon isotopes; Ultra-micro lab balance, Sartorius Cubis II
    Materialart: Dataset
    Format: text/tab-separated-values, 1974 data points
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2023-10-11
    Beschreibung: This dataset contains pooled statistics of stable isotope and shell measurements of individual ostracode valve analyses (IOVA) alongside available in-situ measurements of pH, surface and bottom water temperature (BWT), total number of valves analyzed per site, IOVA-δ¹⁸O, IOVA-δ¹³C, shell mass, shell length/width, along with their average and standard deviations at 17 sites across Lake Turkana, eastern Africa. These modern sediments were collected using a modified Ekman dredge during May to November 1979. The stable isotopic measurements were conducted at the [Paleo² Laboratory at the University of Arizona|https://thirumalai.geo.arizona.edu/] on a Thermo Kiel IV Carbonate Device coupled to a 253 Plus IRMS; the length/width measurements were performed on a MeijiTechno HDZ7000TS Digital Zoom Microscope System, and mass of each valve was measured using a Sartorius Cubis II Ultra-Micro Balance. Details about the materials can be found in https://doi.org/10.1029/2022GC010790
    Schlagwort(e): 79-130F; 79-147F; 79-158F; 79-160F; 79-164F; 79-166F; 79-168F; 79-170F; 79-183F; 79-189F; 79-193F; 79-194F; 79-204F; 79-77F; Bottom water temperature; BS125; BS90; BS91; Digital Zoom Microscope System, MeijiTechno, HDZ7000TS; Distance; EG; Ekman grab; Elevation of event; Event label; lake sediments; Lake Turkana, Africa; Latitude of event; Longitude of event; Mass spectrometer ThermoFisher Scientific 253plus gas coupled to a KIEL IV carbonate preparation device; Number of measurements; Ostracoda, length; Ostracoda, length, standard deviation; Ostracoda, mass; Ostracoda, mass, standard deviation; Ostracoda, δ13C; Ostracoda, δ13C, standard deviation; Ostracoda, δ18O; Ostracoda, δ18O, standard deviation; ostracodes; oxygen and carbon isotopes; pH; Sea surface temperature; Site; Ultra-micro lab balance, Sartorius Cubis II
    Materialart: Dataset
    Format: text/tab-separated-values, 243 data points
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 3 (1995), S. 0 
    ISSN: 1526-100X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Throughout tropical moist climates, Dicranopteris linearis fernlands can develop as a result of rain forest clearance followed by frequent burning. In Sri Lanka, D. linearis fern-lands are capable of suppressing the regeneration of rain forest. Field experiments were conducted at Sinharaja Man and Biosphere Reserve, a rain forest where fernlands occupy substantial areas of the reserve boundary. The experiment's objective was to identify methods for initiating forest regeneration in fernlands dominated by D. linearis Three disturbance treatments were used to initiate seedling regeneration: clean weed, root removal, and till. We hypothesized that increasing the severity of the soil disturbance would establish vegetation with higher species richness and diversity, greater above-ground dry biomass, and higher percentage cover and seedling density. Results indicate only partial support for this hypothesis. Dry biomass was greatest in till treatments, the most severe soil disturbance. By comparison, species richness and diversity, seedling density, and percentage cover were greatest in root-removal treatments, though in many instances the differences were not significant. The study clearly demonstrated that any kind of soil disturbance can facilitate the establishment of herbs, shrubs, and trees in a fernland dominated by D. linearis. Results showed that herbs, sedges, grasses, and pioneer shrubs represented greater proportions of seedling recruits than did pioneer trees. Seedlings of primary-forest tree species were nearly nonexistent. In general, results showed that soil disturbance can play an important role in site preparation for the purpose of initiating non-fern vegetation in fernlands dominated by D. linearis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 688 (1993), S. 0 
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 304 (1983), S. 659-660 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] SEVERAL of Williamson's conclusions on Speciation in the freshwater molluscs of the Turkana Basin1 are based on assumptions which need further examination. Here we comment on some relevant research in the Koobi Fora area. Although the snail faunas collected by Williamson represent 'life and death ...
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Although the effects of climate warming on the chemical and physical properties of lakes have been documented, biotic and ecosystem-scale responses to climate change have been only estimated or predicted by manipulations and models. Here we present evidence that climate warming is diminishing ...
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of paleolimnology 20 (1998), S. 381-407 
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; ostracode ; paleoecology ; Great Salt Lake ; Pliocene ; Pleistocene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract This study summarizes the results of micropaleontological, sedimentological, and isotope geochemical analyses of cuttings from five deep wells drilled in the Great Salt Lake (Utah, USA). Spanning the last 5.0 million yrs, our environmental history of the Great Salt Lake distinguishes four intervals based on paleobiological and sedimentological characteristics, using a previously developed tephrochronology for age control. For most of its history, the Great Salt Lake Basin has been occupied by a mixture of marsh, shallow lacustrine and sand flat conditions. In contrast, open lake conditions, typical of the Bonneville cycles and the modern Great Salt Lake apparently have only dominated the basin for the past 0.6-0.8 Ma. The two main structural basins in the study area (the North and South Basins) experienced different lacustrine histories. Large but frequently saline lakes occupied the North Basin after about 0.6 Ma. In the South Basin, ephemeral, saline lacustrine conditions started at 2.1 Ma and developed to full lacustrine conditions at 0.3 Ma. Our paleoenvironmental interpretations are broadly consistent with the aquatic palynological records from the same wells, as well as with the prior core- and outcrop-based lines of evidence. However, the differences in lake history between the North and South Basin have not been previously recognized.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; paleoclimate ; Great Basin ; environmental magnetism ; paleomagnetic secular variation ; pleistocene ; quaternary
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract This study presents the age control and environmental magnetism components of a new, late Pleistocene paleoclimate record for the Great Basin of western North America. Two new cores from the Summer Lake sub-basin of pluvial Lake Chewaucan, Oregon, USA are correlated to basin margin outcrops on the basis of tephrochronology, lithostratigraphy, sediment magnetism and paleomagnetic secular variation. Eleven tephra layers were found in the cores that correlate to tephra identified previously in the outcrop. The Olema ash was also found in one of the cores; its stratigraphic position, relative to 3 dated tephra layers, indicates that its age is 50-55 ka, somewhat younger than has been previously reported. The Summer Lake sediments are divided into deep and shallow lake lithosomes based on sedimentary features. The stratigraphic position of these lithosomes support the tephra-based correlations between the outcrop and the cores. These sediments contain a well resolved record of the Mono Lake Excursion (MLE) and an earlier paleomagnetic excursion as well as a high quality replication of the paleosecular variation immediately above the MLE. Relative sedimentation rates increased dramatically toward the depocenter during intervals of low-lake level. In contrast, during intervals of high-lake level, relative sedimentation rates were comparable along the basin axis from the basin margin to the depocenter. The magnetic mineralogy of the Summer Lake sediments is dominated by pseudo-single domain (titano)magnetite and intervals of high/low magnetite concentration coincide with lithosomes that indicate high/low lake levels. Magnetic grain size also varies in accord with bulk sediment grain size as indicated by the silt/clay ratio. To a first order, variations in magnetic parameters, especially those attributable to the concentration of magnetic minerals, correlate well with global glacial/interglacial oscillations as indicated by marine oxygen isotope stages. This relationship can be explained by increased dissolution of (titano)magnetite minerals as lake level dropped and the lake became more productive biologically. This inference is supported by a correspondence between lower concentrations of magnetite with higher levels of total organic carbon and vice-versa.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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