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  • 1
    Electronic Resource
    Electronic Resource
    Climate change Snow maker for the ice ages (2005)
    [s.l.] : Nature Publishing Group
    Nature 433 (2005), S. 809-810 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Over the past 50 million years, the Earth's climate has been cooling (Fig. 1). Although Antarctica has been glaciated for at least the past 35 million years, large ice sheets did not appear in the Northern Hemisphere until about 2.7 million years ago. Earth scientists largely agree that ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/433809a
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Palaeoclimate Low-down on a rhythmic high (2004)
    [s.l.] : Nature Publishing Group
    Nature 427 (2004), S. 686-687 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] During the 1920s, Milutin Milankovitch, a Serbian mathematician, calculated the effects of alterations in Earth's motion around the Sun on the amount of solar energy reaching different latitudes. Since then, some of the long-period, cyclic changes seen in archives of past environmental conditions ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/427686a
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    Paper (German National Licenses)
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  • 3
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    (Table 3) Age model of DSDP Hole 75-532 from the Benguela Upwelling System, South Atlantic
    PANGAEA
    Details
    Publication Date: 2023-06-27
    Keywords: 75-532; Age, comment; Age model; Ageprofile Datum Description; Deep Sea Drilling Project; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Leg75; South Atlantic
    Type: Dataset
    Format: text/tab-separated-values, 60 data points
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  • 4
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    Sedimentology and radiolarian distribution in latest Miocene to Recent sediments of ODP Site 75-532 from the Benguela Upwelling System, South Atlantic
    PANGAEA
    Details
    Publication Date: 2023-06-27
    Keywords: 75-532_Site; Accumulation rate, benthic foraminifera by number; Accumulation rate, calcium carbonate; Accumulation rate, radiolarians by number; Accumulation rate, total organic carbon; AGE; Benthic foraminifera of total foram fauna; Calcium carbonate; Carbon, organic, total; COMPCORE; Composite Core; Counting 〉250 µm fraction; Counting 〉45 µm fraction; Deep Sea Drilling Project; Density, dry bulk; DEPTH, sediment/rock; DSDP; DSDP/ODP/IODP sample designation; Foraminifera, planktic; Foraminifera, planktic, fragments; Glomar Challenger; Leg75; Radiolarian preservation; Radiolarians; Radiolarians, intermediate/radiolarians, warm ratio; Radiolarians, intermediate water depth; Radiolarians, temperate; Radiolarians, upwelling; Radiolarians, warm; Sample code/label; Sedimentation rate; South Atlantic; Uvigerina spp.; Uvigerina spp., δ18O
    Type: Dataset
    Format: text/tab-separated-values, 723 data points
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  • 5
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    Late Miocene-early Pliocene stable isotope record of benthic foraminifera from ODP Site 177-1088 in the sub-Antarctic South Atlantic (2002)
    PANGAEA
    In:  Supplement to: Billups, Katharina (2002): Late Miocene through early Pliocene deep water circulation and climate change viewed from the sub-Antarctic South Atlantic. Palaeogeography, Palaeoclimatology, Palaeoecology, 185(3-4), 287-307, https://doi.org/10.1016/S0031-0182(02)00340-1
    Details
    Publication Date: 2024-01-09
    Description: Benthic foraminiferal stable isotope records for the past 11 Myr from a recently drilled site in the sub-Antarctic South Atlantic (Site 1088, Ocean Drilling Program Leg 177, 41°S, 15°E, 2082 m water depth) provide, for the first time, a continuous long-term perspective on deep water distribution patterns and Southern Ocean climate change from the late Miocene through the early Pliocene. I have compiled published late Miocene through Pliocene stable isotope records to place the new South Atlantic record in a global framework. Carbon isotope gradients between the North Atlantic, South Atlantic, and Pacific indicate that a nutrient-depleted watermass, probably of North Atlantic origin, reached the sub-Antarctic South Atlantic after 6.6 Ma. By 6.0 Ma the relative proportion of the northern-provenance watermass was similar to today and by the early Pliocene it had increased to greater than the modern proportion suggesting that thermohaline overturn in the Atlantic was relatively strong prior to the early Pliocene interval of inferred climatic warmth. Site 1088 oxygen isotope values display a two-step increase between ~7.4 Ma and 6.9 Ma, a trend that parallels a published delta18O record of a site on the Atlantic coast of Morocco. This is perhaps best explained by a gradual cooling of watermasses that were sinking in the Southern Ocean. I speculate that relatively strong thermohaline overturn at rates comparable to the present day interglacial interval during the latest Miocene may have provided the initial conditions for early Pliocene climatic warmth. The impact of an emerging Central American Seaway on Atlantic-Pacific Ocean upper water exchange may have been felt in the North Atlantic beginning in the latest Miocene between 6.6 and 6.0 Ma, which would be ~1.5 Myr earlier than previously thought.
    Keywords: 177-1088; COMPCORE; Composite Core; Joides Resolution; Leg177; Ocean Drilling Program; ODP; South Atlantic Ocean
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 6
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    Mg/Ca ratios of Cenozoic benthic foraminifera from the Indian and South Atlantic Ocean (2003)
    PANGAEA
    In:  Supplement to: Billups, Katharina; Schrag, Daniel P (2003): Application of benthic foraminiferal Mg/Ca ratios to questions of Cenozoic climate change. Earth and Planetary Science Letters, 209(1-2), 181-195, https://doi.org/10.1016/S0012-821X(03)00067-0
    Details
    Publication Date: 2024-01-09
    Description: We investigate the evolution of Cenozoic climate and ice volume as evidenced by the oxygen isotopic composition of seawater (delta18Osw) derived from benthic foraminiferal Mg/Ca ratios to constrain the temperature effect contained in foraminiferal delta18O values. We have constructed two benthic foraminiferal Mg/Ca records from intermediate water depth sites (Ocean Drilling Program sites 757 and 689 from the subtropical Indian Ocean and the Weddell Sea, respectively). Together with the previously published composite record of Lear et al. (2002, doi:10.1126/science.287.5451.269) and the Neogene record from the Southern Ocean of Billups and Schrag (2002, doi:10.1029/2000PA000567), we obtain three, almost complete representations of the delta18Osw for the past 52 Myr. We discuss the sensitivity of early Cenozoic Mg/Ca-derived paleotemperatures (and hence the delta18Osw) to assumptions about seawater Mg/Ca ratios. We find that during the middle Eocene (~ 49-40 Ma), modern seawater ratios yield Mg/Ca-derived temperatures that are in good agreement with the oxygen isotope paleothermometer assuming ice-free conditions. Intermediate waters cooled during the middle Eocene reaching minimum temperatures by 40 Ma. The corresponding delta18Osw reconstructions support ice growth on Antarctica beginning by at least 40 Ma. At the Eocene/Oligocene boundary, Mg/Ca ratios (and hence temperatures) from Weddell Sea site 689 display a well-defined maximum. We caution against a paleoclimatic significance of this result and put forth that the partitioning coefficient of Mg in benthic foraminifera may be sensitive to factors other than temperature. Throughout the remainder of the Cenozoic, the temporal variability among delta18Osw records is similar and similar to longer-term trends in the benthic foraminiferal delta18O record. An exception occurs during the Pliocene when delta18Osw minima in two of the three records suggest reductions in global ice volume that are not apparent in foraminiferal delta18O records, which provides a new perspective to the ongoing debate about the stability of the Antarctic ice sheet. Maximum delta18Osw values recorded during the Pleistocene at Southern Ocean site 747 agree well with values derived from the geochemistry of pore waters (Schrag et al., 1996, doi:10.1126/science.272.5270.1930) further highlighting the value of the new Mg/Ca calibrations of Martin et al. (2002, doi:10.1016/S0012-821X(02)00472-7) and Lear et al. (2002, doi:10.1016/S0016-7037(02)00941-9) applied in this study. We conclude that the application of foraminiferal Mg/Ca ratios allows a refined view of Cenozoic ice volume history despite uncertainties related to the geochemical cycling of Mg and Ca on long time scales.
    Keywords: 113-689; 121-757; COMPCORE; Composite Core; Joides Resolution; Leg113; Leg121; Ocean Drilling Program; ODP; South Atlantic Ocean; South Indian Ridge, South Indian Ocean
    Type: Dataset
    Format: application/zip, 6 datasets
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  • 7
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    Sedimentology and radiolarian distribution of latest Miocene to Recent sediments from the Benguela Upwelling System, South Atlantic (2006)
    PANGAEA
    In:  Supplement to: Lazarus, David B; Bittniok, Beatrice; Diester-Haass, Lieselotte; Meyers, Philip A; Billups, Katharina (2006): Comparison of radiolarian and sedimentologic paleoproductivity proxies in the latest Miocene-Recent Benguela Upwelling System. Marine Micropaleontology, 60(4), 269-294, https://doi.org/10.1016/j.marmicro.2006.06.003
    Details
    Publication Date: 2024-01-09
    Description: Estimating past ocean productivity from ocean sediments often gives different results depending on the measurement used. We have examined a suite of paleoproductivity proxies in latest Miocene-Recent sediments from DSDP Site 532 and ODP Site 1084, two deep-sea sections underlying the Benguela Upwelling System off the Atlantic coast of southern Africa. The productivity history of this system has been previously established via organic carbon concentration, diatom floras and alkenone based estimates of surface water temperature, and shows a change from low productivity in the early Pliocene to sustain high productivity in the late Pliocene-Recent. Each of our samples was split and simultaneously analysed for several proxies of ocean productivity, including organic carbon (TOC%), carbonate, abundance of opaline radiolarians, accumulation rate of benthic foraminifera (BFAR); the radiolarian faunal composition indices Upwelling Radiolarian Index (URI) and the Water Depth Ecology index (WADE); other proxies for opal and carbonate dissolution, plus stable isotopes of benthic foraminifera. Comparisons between proxies in the same measured samples, between sites in downcore plots and to the published productivity record for this region suggest that TOC and radiolarian faunal composition, particularly the WADE index, are good indicators of past productivity, albeit with different sensitivities (log-linear correlation WADE-TOC% r=0.78, n=65, p〈0.01). In contrast, carbonate, and carbonatebased proxies such as BFAR primarily reflect changes in dissolution. Radiolarian faunal composition indices do not appear to be affected by bulk opal accumulation or changes in opal preservation. WADE analysis of radiolarian faunas and TOC% measurements appear to be useful proxies for productivity in late Neogene sediments, particularly for sections where opal or carbonate dissolution is significant.
    Keywords: 175-1084A; 75-532; 75-532_Site; Benguela Current, South Atlantic Ocean; COMPCORE; Composite Core; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Joides Resolution; Leg175; Leg75; Ocean Drilling Program; ODP; South Atlantic
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 8
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    Revised geomagnetic polarity timescale for the late Oligocene to early Miocene of ODP Site 177-1090 (2004)
    PANGAEA
    In:  Supplement to: Billups, Katharina; Pälike, Heiko; Channell, James E T; Zachos, James C; Shackleton, Nicholas J (2004): Astronomic calibration of the late Oligocene through early Miocene geomagnetic polarity time scale. Earth and Planetary Science Letters, 224(1-2), 33-44, https://doi.org/10.1016/j.epsl.2004.05.004
    Details
    Publication Date: 2024-01-09
    Description: At Ocean Drilling Program (ODP) Site 1090 (subantarctic South Atlantic), benthic foraminiferal stable isotope data (from Cibicidoides and Oridorsalis) span the late Oligocene through early Miocene (~24-16 Ma) at a temporal resolution of ~5 ky. Over the same interval, a magnetic polarity stratigraphy can be unequivocally correlated to the geomagnetic polarity time scale (GPTS), thereby providing direct correlation of the isotope record to the GPTS. In an initial age model, we use the newly derived age of the Oligocene/Miocene (O/M) boundary of 23.0 Ma of Shackleton et al. (2000, doi:10.1130/0091-7613(2000)28〈447:ACAFTO〉2.0.CO;2), revised to the new astronomical calculation (La2003) of Laskar et al (2004, doi:10.1016/j.icarus.2004.04.005) to recalculate the spline ages of Cande and Kent (1995, doi:10.1029/94JB03098). We then tune the Site 1090 dekta18O record to obliquity using La2003. In this manner, we are able to refine the ages of polarity chrons C7n through C5Cn.1n. The new age model is consistent, within one obliquity cycle, with previously tuned ages for polarity chrons C7n through C6Bn from Shackleton et al. (2000) when rescaled to La2003. The results from Site 1090 provide independent evidence for the revised age of the Oligocene/Miocene boundary of 23.0 Ma. For early Miocene polarity chrons C6AAr through C5Cn, our obliquity-scale age model is the first to allow a direct calibration to the GPTS. The new ages are generally within one obliquity cycle of those obtained by rescaling the Cande and Kent (1995) interpolation using the new age of the O/M boundary (23.0 Ma) and the same middle Miocene control point (14.8 Ma) used by Cande and Kent (1995).
    Keywords: 177-1090; COMPCORE; Composite Core; Joides Resolution; Leg177; Ocean Drilling Program; ODP; South Atlantic Ocean
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 9
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    Stable oxygen isotope ratios of planktonic foraminifera (Appendix A) (2006)
    PANGAEA
    In:  Supplement to: Billups, Katharina; Lindley, Carolyn; Fisler, J; Martin, Pamela (2006): Mid Pleistocene climate instability in the subtropical northwestern Atlantic. Global and Planetary Change, 54(3-4), 251-262, https://doi.org/10.1016/j.gloplacha.2006.06.025
    Details
    Publication Date: 2024-01-09
    Description: We present Globigerinoides ruber, G. sacculifer and Neogloboquadrina dutertrei oxygen isotope records from northwestern subtropical Atlantic Site 1058 spanning the mid Pleistocene (~600 to 400 ka). The high temporal resolution of these records (~800 yr) allows us to compare millennial-scale climate signals during one of the most extreme glacial periods of the Pleistocene (Marine Isotope Stage (MIS) 12) to an earlier, less extreme glacial (MIS 14), as well as to two full interglacial intervals (MIS 13 and MIS 15). We observe excellent agreement in the timing and amplitude of variations between the surface-most dwelling species G. ruber and Northern Hemisphere insolation during the two interglacial periods. There is some expression of Northern Hemisphere insolation during glacial MIS 14; however, during the more extreme glacial MIS 12 Northern Hemisphere insolation patterns are not apparent in any of the planktonic foraminiferal d18O records. Insolation remains relatively high, but d18O values increase toward the characteristic d18O maximum of MIS 12 in all three of the records. On the millennial-scale, all three species display their highest amplitude d18O variations (with a period between 4–6 kyr) during glacial MIS 12. Suborbital-scale variability is also statistically significant during glacial MIS 14, but the amplitude is smaller. These results support hypotheses linking millennial-scale climate fluctuations to the extent of continental glaciation. We propose that the relatively high degree of sea surface instability during one of the most extreme glacial periods of the Pleistocene arises from the competing effects of strong atmospheric winds related to the presence of a large ice sheet to the north and persistently high incident solar radiation during this interval of time.
    Keywords: 172-1058; AGE; Blake Outer Ridge, North Atlantic Ocean; COMPCORE; Composite Core; DEPTH, sediment/rock; DSDP/ODP/IODP sample designation; Globigerinoides ruber, δ18O; Globigerinoides sacculifer, δ18O; Joides Resolution; Leg172; Mass spectrometer GV Instruments Isoprime; Neogloboquadrina dutertrei, δ18O; Ocean Drilling Program; ODP; Sample code/label
    Type: Dataset
    Format: text/tab-separated-values, 1203 data points
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  • 10
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    (Appendix A) Radiolarian abundances in ODP Hole 175-1084A (2008)
    PANGAEA
    In:  Supplement to: Lazarus, David B; Bittniok, Beatrice; Diester-Haass, Lieselotte; Billups, Katharina; Ogawa, Yujiro; Takahashi, Kozo; Meyers, Philip A (2008): Radiolarian and sedimentologic paleoproductivity proxies in late Pleistocene sediments of the Benguela Upwelling System, ODP Site 1084. Marine Micropaleontology, 68(3-4), 223-235, https://doi.org/10.1016/j.marmicro.2008.02.004
    Details
    Publication Date: 2024-01-09
    Description: The changing composition of radiolarian faunas from late Neogene deep-sea sediments has been used in recent years as a proxy for changes in marine paleoproductivity. We examine radiolarian faunas, organic carbon content (TOC), opal and coarse-fraction components over the last 270,000 years in sediments from ODP Hole 1084A, drilled in a high productivity upwelling region within the Benguela Upwelling System off the west coast of Africa. Age control is provided by stable oxygen isotope measurements of benthic foraminifera. Prior research has established that late Pleistocene glacial intervals in this upwelling system generally had higher productivity than interglacials. The radiolarian WADE (water-depth ecology) paleoproductivity index correlates well with TOC and opal in these samples, and all three parameters change in synchrony with the benthic isotope curve over all but the MIS 5e–6 time interval. WADE inferred productivity is significantly higher in glacials than interglacials. We conclude that the WADE index is a useful proxy for paleoproductivity at this location, as are also opal and organic carbon accumulation rates. Carbonate and carbonate based indices such as the accumulation rate of benthic foraminifera (BFAR) by contrast do not correlate well either to productivity indices or to the glacial–interglacial cycle, and are interpreted to primarily reflect carbonate dissolution.
    Keywords: 175-1084A; Acanthosphaera corlocae; Accumulation rate, benthic foraminifera by number; Accumulation rate, mass; Acrosphaera murrayana; Actinomma antarcticum; Actinomma boreale; Actinomma leptodermum; Actinomma popofskii; AGE; Amphirhopalum ypsilon; Antarctissa spp.; Anthocyrtidium ophirense; Anthocyrtidium zanguebaricum; Arachnocorys circumtexta; Benguela Current, South Atlantic Ocean; Botryocyrtis scutum; Botryostrobus aquilonaris; Botryostrobus auritus/australis; Calcium carbonate; Calculated; Carbon, organic, total; Carpocaniidae indeterminata; Cladococcus sp.; Cornutella profunda; Counting 〉150 µm fraction; Counting 〉45 µm fraction; Cycladophora bicornis; Cycladophora conica; Cycladophora davisiana; Cyrtopera laguncula; DEPTH, sediment/rock; Dictiocoryne profunda; Dictyophimus crisiae; Dictyophimus infabricatus; Didymocyrtis tetrathalamus; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Element analyser CHNS-O; Eucyrtidium acuminatum; Eucyrtidium calvertense; Eucyrtidium teuscheri group; Heliodiscus asteriscus; Helotholus histricosa; Joides Resolution; Lamprocyclas maritalis; Lamprocyrtis heteroporos; Lamprocyrtis nigriniae; Larcopyle buetschlii; Leg175; Lipmanella dictyoceras; Lithelius minor; Lithomelissa hystrix; Lithomelissa setosa; Lithostrobus hexagonalis; Lophospyris pentagona; Mass spectrometer GV Instruments Isoprime; Ocean Drilling Program; Octopyle stenozona; ODP; Ommatodiscus irregularis; Opal, biogenic silica; Opal, extraction; Mortlock & Froelich, 1989; Peripyramis circumtexta; Phelodinium cranwelliae; Phormospyris stabilis stabilis; Phormostichoartus corbula; Phormostichoartus pitomorphus group; Plectacantha cresmastoplegma; Primary production of carbon; Prunopyle antarctica; Pseudodictyophimus gracilipes; Pterocanium auritum; Pterocanium hirundo group; Pterocanium praetextum praetextum; Pterocanium trilobum; Pterocorys minythorax; Pterocorys zancleus; Radiolarians; Radiolarians, intermediate/radiolarians, warm ratio; Radiolarians, intermediate water depth; Radiolarians, other; Radiolarians, temperate; Radiolarians, upwelling; Radiolarians, warm; Saccospyris antarctica; Sample code/label; Siphocampe arachnea; Spirocyrtis spp.; Spongocore cylindrica; Spongopyle osculosa group; Spongotrochus venustum; Stichocorys peregrina; Theocorys veneris; Theocorythium trachelium; Uvigerina spp.; Uvigerina spp., δ18O; Zygocircus spp.
    Type: Dataset
    Format: text/tab-separated-values, 2976 data points
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