search
Include:
534 Research products, page 1 of 54

  • Research data
  • Other dataset type
  • Digital Humanities and Cultural Heritage

10
arrow_drop_down
Relevance
arrow_drop_down
  • Open Access English
    Authors: 
    Conesa, Gilles A R; Favre, Eric; Münch, Philippe; Dalmasso, Hélène; Chaix, Christian;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    The Southern Marion Plateau (SMP) represents a vertical stacking of Miocene carbonate platform deposits. Two sites (1196 and 1199) were drilled on top of this plateau, penetrating a 663-m carbonate succession of bioclastic and reefal sedimentary bodies. The study focuses on the least dolomitized 410-m-thick upper part of the succession, which is middle to late Miocene in age. Sedimentological and paleontological studies were conducted at both sites in order to propose a paleoenvironmental model and its evolution through the Miocene age. Six main microfacies of possible environmental significance were defined using statistical multivariate analyses, based on the recognition and point counting of 24 biogenic components. Depositional environment reconstructions are proposed as well as the biosedimentary and the environmental evolution regarding seismic architectures, stratigraphy, biosedimentology, and microfacies analysis. The SMP platform mainly results from a vertical stacking of lens-shaped bodies in homoclinal to distally steepened ramp settings.

  • English
    Authors: 
    Rachmayani, Rima; Prange, Matthias; Schulz, Michael;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Using the Community Climate System Model version 3 (CCSM3) including a dynamic global vegetation model, a set of 13 time slice experiments was carried out to study global climate variability between and within the Quaternary interglacials of Marine Isotope Stages (MISs) 1, 5, 11, 13, and 15. The selection of interglacial time slices was based on different aspects of inter- and intra-interglacial variability and associated astronomical forcing. The different effects of obliquity, precession, and greenhouse gas (GHG) forcing on global surface temperature and precipitation fields are illuminated. In most regions seasonal surface temperature anomalies can largely be explained by local insolation anomalies induced by the astronomical forcing. Climate feedbacks, however, may modify the surface temperature response in specific regions, most pronounced in the monsoon domains and the polar oceans. GHG forcing may also play an important role for seasonal temperature anomalies, especially at high latitudes and early Brunhes interglacials (MIS 13 and 15) when GHG concentrations were much lower than during the later interglacials. High- versus low-obliquity climates are generally characterized by strong warming over the Northern Hemisphere extratropics and slight cooling in the tropics during boreal summer. During boreal winter, a moderate cooling over large portions of the Northern Hemisphere continents and a strong warming at high southern latitudes is found. Beside the well-known role of precession, a significant role of obliquity in forcing the West African monsoon is identified. Other regional monsoon systems are less sensitive or not sensitive at all to obliquity variations during interglacials. Moreover, based on two specific time slices (394 and 615 ka), it is explicitly shown that the West African and Indian monsoon systems do not always vary in concert, challenging the concept of a global monsoon system on astronomical timescales. High obliquity can also explain relatively warm Northern Hemisphere high-latitude summer temperatures despite maximum precession around 495 ka (MIS 13). It is hypothesized that this obliquity-induced high-latitude warming may have prevented a glacial inception at that time.

  • English
    Authors: 
    Bohleber, Pascal; Sold, Leo; Hardy, Douglas R; Schwikowski, Margit; Klenk, Patrick; Fischer, Andrea; Sirguey, Pascal; Cullen, Nicolas J; Potocki, Mariusz; Hoffmann, Helene; +1 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Although its Holocene glacier history is still subject to debate, the ongoing iconic decline of Kilimanjaro's largest remaining ice body, the Northern Ice Field (NIF), has been documented extensively based on surface and photogrammetric measurements. The study presented here adds, for the first time, ground-penetrating radar (GPR) data at center frequencies of 100 and 200 MHz to investigate bedrock topography, ice thickness and internal stratigraphy at NIF. The direct comparison of the GPR signal to the visible glacier stratigraphy at NIF's vertical walls is used to validate ice thickness and reveals that the major internal reflections seen by GPR can be associated with dust layers. Englacial reflections can be traced consistently within our 200 MHz profiles, indicating an undisturbed internal stratigraphy within NIF's central flat area. We show that it is possible to follow isochrone layers between two former NIF ice core drilling sites and a sampling site on NIF's vertical wall. As a result, these isochrone layers provide constraints for future attempts at linking age-depth information obtained from multiple locations at NIF. The GPR profiles reveal an ice thickness ranging between (6.1 �� 0.5) and (53.5 �� 1.0) m. Combining these data with a very high resolution digital elevation model we spatially extrapolate ice thickness and give an estimate of the total ice volume remaining at NIF's southern portion as (12.0 �� 0.3) 10**6 m**3. In summer 2015, a ground-penetrating radar (GPR) survey was carried out at Kilimanjaro's largest remaining ice body, the Northern Ice Field (NIF). Two GPR systems at center frequencies of 100 and 200 MHz were used to investigate bedrock topography, ice thickness and internal stratigraphy at NIF. A photometric estimation of the height of NIF's vertical wall was used to validate ice thickness inferred from GPR using a constant wave speed of 0.168 m/ns. The GPR profiles revealed an ice thickness ranging between (6.1 �� 0.5) and (53.5 �� 1.0) m. These data were combined with a very high resolution digital elevation model in order to spatially extrapolate ice thickness and give an estimate of the total ice volume remaining at NIF's southern portion.

  • English
    Authors: 
    Westerhold, Thomas; R��hl, Ursula; Wilkens, Roy H; P��like, Heiko; Lyle, Mitchell W; Dunkley Jones, Tom; Bown, Paul R; Moore, Ted; Kamikuri, Shin-Ichi;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Integrated Ocean Drilling Program (IODP) Expedition 320 recovered high-quality paleomagnetic records with over 800 dated reversals and decimeter-scale cyclic sediments which provide an outstanding framework to inter-calibrate major fossil groups and refine magnetic polarity chrons for the early Miocene, the entire Oligocene and the late Eocene Epoch. In order to reconstruct the climate history of the Equatorial Pacific one of the major objectives of the Pacific Equatorial Age Transect (PEAT) is the compilation of a Cenozoic Megasplice which integrates all available bio-, chemo-, and magnetostratigraphic data including key records from Ocean Drilling Program (ODP) Leg 199.Here we present extended post-cruise refinements of the shipboard composite depth scales and composite records of IODP Expedition 320 Sites U1331, U1332, U1333, U1334 as well as ODP Leg 199 Sites 1218, 1219 and 1220. The revised composite records were used to perform a site-to-site correlation and integration of Leg 199 and Exp. 320 sites. Based on this decimeter scale correlation a high resolution integrated paleomagnetic and biostratigraphic framework for the Equatorial Pacific is established covering the time from 20 to 40 Ma. This unprecedented sedimentary compendium from the Equatorial Pacific will be the backbone for paleoceanographic reconstructions for the late Paleogene.

  • Open Access English
    Authors: 
    Beaudouin, Célia; Jouet, Gwenael; Suc, Jean-Pierre; Berné, Serge; Escarguel, Gilles;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Palynology has been performed for the first time on Late Quaternary sediments of the Gulf of Lions. The aim is both to tighten the chronology of seismic profiles in the region, and to elucidate the vegetation of southern France during the Last Climatic Cycle. Four cores, taken on the shelf, mostly record Marine Isotope Stages (MIS) 1 and 2 and part of MIS 3 and MIS 5. The latter sediments might have been preserved in a paleodepression on the emergent shelf between the Rhône and the Hérault rivers. It would explain their preservation against transgression and regression erosions of more recent stages. This study also provides a synthesis of palynological continental data collected during the last 40 years in southern Europe. Preliminary comparisons made between the latter and new marine data demonstrate that refugia of Picea and Abies existed in southern France during MIS 3 and MIS 2. The dynamics of Artemisia, deciduous Quercus and Corylus, Abies and finally Fagus is also reconstructed for the last deglaciation. First results obtained in the Gulf of Lions confirm and complete that synthesis.

  • English
    Authors: 
    Tamborrino, Leonardo; Himmler, Tobias; Elvert, Marcus; Conti, Daniel; Gualtieri, Alessandro F; Fontana, Daniela; Bohrmann, Gerhard;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Tubular carbonate conduits (TCC) represent the termination of fluid plumbing systems in environments of hydrocarbon seepage and play a relevant role in the discharge of methane from sub-seafloor sediments to the water column. However, the biogeochemical reactions and biological activities involved in their formation are not fully understood. To address this, TCC samples were collected with a remotely operated vehicle from the seabed on the SW flank of the Athina mud volcano in the eastern Mediterranean Sea. Petrographic, mineralogical, stable carbon and oxygen isotope and lipid biomarker analyses were performed to elucidate the formation processes of the tubular carbonates. Clotted and fibrous aragonite form the internal lining of the cavities, while the outer portion of the tubes is formed by micritic Mg-calcite cementing hemipelagic sediment. 13C-depleted Mg-calcite and aragonite (as low as ���14.4��� V-PDB) and lipid biomarkers (archaeol, ���89.8��� V-PDB) indicate that carbonate precipitation was influenced by sulfate-dependent anaerobic oxidation of methane (AOM). AOM locally enhances aragonite precipitation, thereby facilitating early lithification of the conduits within the mud volcano sediments. The size and morphology of the TCC comparable with the buried portion of tubeworm colonies found in the proximity of the sampling site. However, our results suggest that TCC likely formed by the action of burrowing organism rather than being mineralizations of the tubeworm colonies. This study provides new insights into the interpretation and understanding of TCC, highlighting the role of macrofaunal activity in the formation of migration pathways for hydrocarbon-rich fluids on the flank of a mud volcano.

  • English
    Authors: 
    Abdul Aziz, Hayfaa; Di Stefano, Agata; Foresi, L M; Hilgen, Frederik J; Iaccarino, Silvia Maria; Kuiper, Klaudia F; Lirer, Fabrizio; Salvatorini, G; Turco, Elena;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    An integrated magneto-biostratigraphic framework is presented for Middle Miocene sediments of DSDP Site 372 located in the Western Mediterranean. Detailed biostratigraphic analysis shows a nearly complete sequence of early Middle Miocene calcareous plankton bioevents in the Mediterranean, including the LCO (Last Common Occurrence) of the nannofossil Sphenolithus heteromorphus which has been astronomically dated in the Ras il Pellegrin (RIP) section on Malta Island [Abels, H.A., Hilgen, F.J., Krijgsman, W., Kruk, R.W., Raffi, I., Turco, E., Zachariasse, W.J., 2005. Long-period orbital control on middle Miocene global cooling: integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta, Paleoceanography, 20, PA4012. doi:10.1029/2004PA001129. 11 pp]. Thermal demagnetization of discrete samples revealed a characteristic low-temperature component with dual polarities despite a weak paleomagnetic signal. The resultant magnetostratigraphic record, combined with the calcareous plankton biostratigraphy, is straightforwardly correlated to the geomagnetic polarity time scale (CK95) of Cande and Kent [Cande, S.C., Kent, D.V., 1995. Revised calibration of the Geomagnetic Polarity Time Scale for the Late Cretaceous and Cenozoic, J. Geophys. Res., 100, 6093-6095] and the Astronomical Tuned Neogene Time Scale (ATNTS04) of Lourens et al. [Lourens, L.J., Hilgen, F.J., Laskar, J., Shackleton, N.J., Wilson, D., 2004. The Neogene Period. In: Gradstein F.M., Ogg J.G., Smith A.G. (Eds.), A Geologic Time Scale, Cambridge Univ. Press, pp. 409-440]. The subchrons recorded in Site 372 succession range from C5Br up to C5AAr. To confirm the magnetostratigraphic calibration, 40Ar/39Ar dating was performed on feldspar of two volcanic ash layers. The radio-isotopic dating indicates a younger age for these two ash layers compared to the magnetostratigraphic calibrated ages according to the CK95 and ATNTS04 age models. However, if the astronomically calibrated age of 28.21 +/- 0.04 Ma is used for the Fish Canyon standard (FCs), the age for the older ash layer exactly matches its ATNTS04 age. Ages for bioevents were calculated assuming constant sedimentation rates between magnetostratigraphic age-tie points. The S. heteromorphus LCO has an age of 13.54 Ma and 13.63 Ma according to CK95 and ATNTS04, respectively, which is consistent with the astronomical tuned age of 13.65 Ma determined at RIP section [Abels, H.A., Hilgen, F.J., Krijgsman, W., Kruk, R.W., Raffi, I., Turco, E., Zachariasse, W.J., 2005. Long-period orbital control on middle Miocene global cooling: integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta, Paleoceanography, 20, PA4012. doi:10.1029/2004PA001129. 11 pp]. We therefore conclude that the magnetostratigraphic calibration of DSDP Site 372 is correct and that, for the time being, this site can be considered as a reference section for the early Middle Miocene of the Mediterranean region.

  • Open Access English
    Authors: 
    Diez, Anja; Eisen, Olaf; Hofstede, Coen Matthijs; Bohleber, Pascal; Polom, Ulrich;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Two seismic surveys were carried out on the high-altitude glacier saddle, Colle Gnifetti, Monte Rosa, Italy/Switzerland. Explosive and vibroseismic sources were tested to explore the best way to generate seismic waves to deduce shallow and intermediate properties (<100 m) of firn and ice. The explosive source (SISSY) excites strong surface and diving waves, degrading data quality for processing; no englacial reflections besides the noisy bed reflector are visible. However, the strong diving waves are analyzed to derive the density distribution of the firn pack, yielding results similar to a nearby ice core. The vibrator source (ElViS), used in both P- and SH-wave modes, produces detectable laterally coherent reflections within the firn and ice column. We compare these with ice-core and radar data. The SH-wave data are particularly useful in providing detailed, high-resolution information on firn and ice stratigraphy. Our analyses demonstrate the potential of seismic methods to determine physical properties of firn and ice, particularly density and potentially also crystal-orientation fabric. Seismic data from three different sources: - SISSY detonation cardridges- ELVIS microvibrator p-wave- ELVIS microvibrator s-waveData were recorded with single-spiked vertical and horizontal component geophones, depending on year. Recording took place in 2008 and 2010.

  • Research data . Other dataset type . 2020
    English
    Authors: 
    Mojtabavi, Seyedhamidreza; Wilhelms, Frank; Cook, Eliza; Davies, Siwan M; Sinnl, Giulia; Skov Jensen, Mathias; Dahl-Jensen, Dorthe; Svensson, Anders M; Vinther, Bo Møllesøe; Kipfstuhl, Sepp; +9 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    This paper provides the first chronology for the deep ice core from the East GReenland Ice-core Project (EGRIP) over the Holocene and late last glacial period. We rely mainly on volcanic events and common patterns of peaks in dielectric profiling (DEP), electrical conductivity measurements (ECM) and tephra records for the synchronization between the EGRIP, NEEM and NGRIP ice cores in Greenland. We transfer the annual-layer-counted Greenland Ice Core Chronology 2005 (GICC05) timescale from the NGRIP core to the EGRIP ice core by means of 373 match points. The NEEM ice core is only used for supporting match-point identification. We name our EGRIP time scale GICC05-EGRIP-1. Over the uppermost 1383.84 m, we establish a depth–age relationship dating back to 14,965 a b2k (years before the year 2000 CE). Tephra horizons provide an independent validation of our match points. In addition, we compare the ratio of annual layer thicknesses between ice cores in-between the match points to assess our results in view of the different ice-flow patterns and accumulation regimes of the different periods and geographical regions. This initial timescale is the basis of interpretation and refinement of the presently derived EGRIP high-resolution data sets of chemical impurities.

  • Open Access English
    Authors: 
    Sjolte, Jesper;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    This dataset contains the time series (1241-1970 CE) of the first two principal components (PCs) of reconstructed winter (DJF) Sea Level Pressure (SLP) in the North Atlantic region (20-70N, 90W-40E). The SLP is reconstructed by matching modeled d18O patterns from an isotope enabled climate model simulation to the spatio-temporal variability of the winter d18O from Greenland ice cores, and extracting the model SLP from an ensemble of the best matching years. PC1 of reconstructed SLP corresponds to the North Atlantic Oscillation, and PC2 of reconstructed SLP corresponds to the Eastern Atlantic pattern. Both time series are normalized and centred. The sign of the data series is as shown in Figure 2 of Sjolte et al. (2018) with the corresponding spatial patterns shown in Supplementary Figure S3. For example, positive values of PC1 means positive NAO, while positive values of PC2 means negative pressure anomalies south of Greenland.

Send a message
How can we help?
We usually respond in a few hours.