ALBERT

Beschreibung: Fluid dynamical simulations were carried out in order to investigate the effect of the large-scale mantle flow field and the depth of the plume source on the structure of the Iceland plume through time. The time-dependent location and shape of the plume in the Earth's mantle was calculated in a global model and it was refined in the upper mantle using a 3D Cartesian model box. Global flow was computed based on density heterogeneities derived from seismic tomography. Plate motion history served as a velocity boundary condition in both models. Hotspot tracks of the plume conduits and the plume head were calculated and compared to actual bathymetry of the North Atlantic. If a plume source in the lowermost mantle is assumed, the calculated surface position of the plume conduit has a southward component of motion due to southward flow in the lower mantle. Depending on tomography model, assumed plume age and buoyancy the southward component is more or less dominating. Plume models having a source at the 660 km discontinuity are only influenced by flow in the upper mantle and transition zone and hence rather yield westward hotspot motion. Many whole-mantle plume models result in a V-shaped track, which does not match the straight Greenland–Iceland–Faroe ridge. Models without strong southward motion, such as for a plume source at 660 km depth, match actual bathymetry better. Plume tracks were calculated from both plume conduits and plume heads. A plume head of 120 K anomalous temperature gives the best match between plume head track and bathymetry.

Beschreibung: Interlaboratory comparisons involving nine European stable isotope laboratories have shown that the routine methods of cellulose preparation resulted in data that generally agreed within the precision of the isotope ratio mass spectrometry (IRMS) method used: +/- 0.2% for carbon and +/- 0.3% for oxygen. For carbon, the results suggest that holocellulose is enriched up to 0.39% in C-13 relative to the purified alpha-cellulose. The comparisons of IRMS measurements of carbon on cellulose, sugars, and starches showed low deviations from -0.23 to +0.23% between laboratories. For oxygen, IRMS measurements varied between means from -0.39 to 0.58%, -0.89 to 0.42%, and -1.30 to 1.16% for celluloses, sugars, and starches, respectively. This can be explained by different effects arising from the use of low- or high-temperature pyrolysis and by the variation between laboratories in the procedures used for drying and storage of samples. The results of analyses of nonexchangeable hydrogen are very similar in means with standard deviations between individual methods from +/- 2.7 to +/- 4.9%. The use of a one-point calibration (IAEA-CH7) gave significant positive offsets in delta H-2 values up to 6%. Detailed analysis of the results allows us to make the following recommendations in order to increase quality and compatibility of the common data bank: (1) removal of a pretreatment with organic solvents, (2) a purification step with 17% sodium hydroxide solution during cellulose preparation procedure, (3) measurements of oxygen isotopes under an argon hood, (4) use of calibration standard materials, which are of similar nature to that of the measured samples, and (5) using a two-point calibration method for reliable result calculation.

Beschreibung: The aim of this work is the implementation of an effective Tsunami Early Warning System for the Indian Ocean. It is a component part of an Early Warning System that will also be capable of registering other natural disasters such as earthquakes and volcanic eruptions. The system integrates terrestrial observation networks of seismology und geodesy with marine measurements techniques and satellite observations. The required R & D work will be realized within the framework of a stage-plan, which will, within a short time span of 1-3 years, be able to provide effective warning on the one hand and, which will also allow for an integration of technological developments, currently undergoing further research. The initiative is coordinated by the Helmholtz Association of German Research Centres (HGF), represented by the GeoForschungsZentrum Potsdam (GFZ). In view of the geological situation one has to bear in mind that Indonesia especially, due to the fact that the main islands are located next to and above the Sunda seismogenic zone, could most frequently and most intensively in the future be prone to catastrophic Tsunami events. The envisaged Early Warning System for the Indian Ocean consists of different components as broadband seismometers, GPS, tide gauges, ocean-bottom pressure sensors and GPS-Buoys. On the basis of the data and recordings registered a warning can be generated. This presentation gives insight into the creation of the 26 December 2004 Tsunami, introduces the planned technical realization of the Early Warning System, shows first model scenarios and gives an overview of the planned realization of an Early Warning System in the Indian Ocean.

Beschreibung: Lateglacial and Holocene faunal and stable-isotope records from benthic foraminifers in the eastern Mediterranean Sea (EMS) suggest a high spatiotemporal variability of deep-water oxygenation and biogeochemical processes at the sea floor during that time. Changes in the oxygenation and food availability of the deep-sea ecosystems are closely linked to the hydrology of the EMS borderlands; they reflect orbital and suborbital climate variations of the high northern latitudes and the African monsoon system. During the last glacial maximum, cool surface waters and high evaporation resulted in maximum convection and oxic deep-waters in all sub-basins. Strong wind-induced mixing fostered surface-water production with seasonal phytodetritus fluxes. During the glacial termination and the Holocene, oxygenation and food availability of deep-sea benthic ecosystems were characterized by a pronounced regional differentiation. Local deep-water formation and trophic conditions were particularly variable in the northern Aegean Sea as a response to changes in riverine runoff and Black Sea outflow. During the interval of sapropel S1 formation in the early Holocene, average oxygen levels decreased exponentially with increasing water depth, suggesting a basin-wide shallowing of vertical convection superimposed by local signals. In the northernmost Aegean Sea, deep-water ventilation persisted during the early period of S1 formation, owing to temperature-driven local convection and the absence of low-salinity Black Sea outflow. At the same time, severe temporary anoxia occurred in the eastern Levantine basin at water depths as shallow as 900 m. This area was likely influenced by enhanced nutrient input of the Nile river that resulted in high organic matter fluxes and related high oxygen-consumption rates in the water column. In the southern Aegean and Levantine Seas, we observe a gradual increase in deep-water residence times, preceding S1 formation by approximately 1–1.5 kyr. Once oxygen levels fell below a critical threshold, the benthic ecosystems collapsed almost synchronously with the onset of S1 deposition. The recovery of benthic ecosystems during the terminal phase of S1 formation is controlled by subsequently deeper convection and re-ventilation over a period of approximately 1500 years. After the re-ventilation of the various sub-basins had been completed during the middle and late Holocene, deep-water renewal was more or less similar to recent rates. During that time, deep-sea ecosystem variability was driven by short-term changes in food quantity and quality as well as in seasonality, all of which are linked to millennial-scale changes in riverine runoff and associated nutrient input.

Beschreibung: Field-aligned currents (FACs) are an important mechanism for transporting energy and momentum from the solar wind into the upper atmosphere at high latitudes. The efficiency of energy dissipation depends on the ionospheric conductivity and the transverse scale size of the field-aligned current circuits. According to Vogt (2002) the conversion of electric current into heat should be most effective for scales of the order of some 10 km when typical ionospheric conductivities are considered. In order to test this conclusion we have performed a statistical analysis with FACs of various scale sizes. This study is based on observations that are derived from CHAMP magnetic field measurements taken during the years 2002-2005. FAC densities within the medium-scale wavelength band of 15-150 km and large-scale FACs (〉150 km) are considered separately and their distributions are compared. The thermospheric mass density recorded simultaneously by CHAMP is used as a measure for the heat deposited in the ionospheric E-layer. The relation between current strength of the two FAC types and thermospheric heating is determined in a superposed epoch analysis. The analysis is performed separately for each season and covers all local time sectors.

Beschreibung: We present a new interface between the geochemical simulator PHREEQC and the open source language R. It represents a tool to flexibly and efficiently program and automate every aspect of geochemical modelling. The interface helps particularly to setup and run large numbers of simulations and visualise the results. Also profiting of numberless high-quality R extension packages, performing sensitivity analysis or Monte Carlo simulations becomes straightforward. Further, an algorithm to speedup reactive transport simulations starting from homogeneous or zone- homogeneous state is programmed and successfully evaluated through the interface. It proved effective and could therefore be included in any reactive transport simulator.

Beschreibung: Rare earth element distribution of mineral, geothermal and surface waters are discussed. The causes of the evidently natural Ce, Eu, and Y anomalies as well as the anthropogenic Gd anomaly are described. For crustal waters it is suggested to apply the REE/Ca abundance ratios rather than the REE abundances because of the less scatter of patterns achieved. The rock-normalised patterns show rock-specific signatures of the waters. The Gd anomaly can be applied as a conservative tracer in hydrological studies.

Beschreibung: An important question in geophysics is whether earthquakes (EQs) can be anticipated prior to their occurrence. Pre-seismic electromagnetic (EM) emissions provide a promising window through which the dynamics of EQ preparation can be investigated. However, the existence of precursory features in pre-seismic EM emissions is still debatable: in principle, it is difficult to prove associations between events separated in time, such as EQs and their EM precursors. The scope of this paper is the investigation of the pre-seismic EM activity in terms of complexity. A basic reason for our interest in complexity is the striking similarity in behavior close to irreversible phase transitions among systems that are otherwise quite different in nature. Interestingly, theoretical studies (Hopfield, 1994; Herz and Hopfield 1995; Rundle et al., 1995; Corral et al., 1997) suggest that the EQ dynamics at the final stage and neural seizure dynamics should have many similar features and can be analyzed within similar mathematical frameworks. Motivated by this hypothesis, we evaluate the capability of linear and non-linear techniques to extract common features from brain electrical activities and pre-seismic EM emissions predictive of epileptic seizures and EQs respectively. The results suggest that a unified theory may exist for the ways in which firing neurons and opening cracks organize themselves to produce a large crisis, while the preparation of an epileptic shock or a large EQ can be studied in terms of “Intermittent Criticality”.

Beschreibung: We studied 40 artesian wells (AWs) in the Amu Darya Delta. These wells include high-salinity (∼ 52 g/l) and saline (5 – 24 g/l) waters but are mostly low-salinity waters (1.3 – 2.9 g/l). The low-salinity AWs cluster into three types, reflecting the variable mixing of different end-member solutes: (residual) brines and solutes deriving from silicate alteration, dissolution of limestone and dissolution of gypsum. The solutes are all undersaturated in calcite and gypsum, contain a substantial cation excess against dissolved inorganic carbon and are characterised by low Ca/SO4 ratios. On the basis of the hydrochemical mass budgets of model cases, we demonstrate that Na-rich Cl-brines (45-48%) and a Na2SO4-brine (30-47%) are the dominant solute components. The solutes derived from aluminium silicate alteration are minor components (7.3 – 19.4%). Even less important are solutes from limestone or gypsum dissolution (0.05 – 3.7%). These waters are unlikely to have originated from sediments hosting gypsum. The low-salinity AWs must have acquired their dominant hydrochemical signatures under non-equilibrium conditions between their remote (unknown) seepage areas and their discharge locations. This acquisition may have begun during the early hydrochemical groundwater evolution when meteoric or surface water passed the critical zone under an arid climate regime. Warmer saline AWs (∼40°C) hosted in deeper Cretaceous formations contain a high portion of NaCl-rich brine (85%) and some are saturated in gypsum. These waters were derived from fluids rising along faults from pre-Cretaceous strata. The high-salinity and relatively cold AWs discharge close to the retreating Aral Sea south of its western basin. These AWs are suboxic, and Si concentrations are very low. The AW hydrochemical signatures reflect the dissolution of halite and gypsum. We observed positive correlations between temperature, Br, B and Si. The temperature correlation with bromide likely documents the transformation of organically bound Br. The silica concentrations in low-salinity AWs southeast of the Aral Sea (eastern basin) are close to quartz saturation and define a chemical Si-geothermometer.

Beschreibung: The use of stable isotopes as climate proxies is widely accepted for climate reconstruction. Re-establishing climate signals, e.g. temperature, from isotope values of biological materials requires some knowledge of the system’s response behaviour. The related problems are discussed in conjunction with stable isotopes of two different terrestrial archives: carbon isotope data of tree rings from southern Germany and oxygen isotope data of diatoms from Lake Holzmaar, Germany. Carbon isotope temperature coefficients (Δδ13C/ΔT) derived from tree rings were chosen as an example for non-linear transformation of environmental signals through biological systems explaining negative and positive temperature coefficients. Thin radial tree ring sections taken from tree rings of different species (poplar, beech and oak) show carbon isotope variations of up to 3‰ with a characteristic, annually recurring isotope pattern. This behaviour is discussed in view of time resolution, isotope signature conservation and the question of storage and remobilisation of photosynthates with time. For Lake Holzmaar it is shown that isotope proxy signals derived from diatoms may not be unambiguously translated into abiotic environmental forcing factors, such as for example temperature. Corresponding measurements reveal that the isotopic input signal varies considerably and nonlinearly with temperature.

Beschreibung: In contrast to predominantly hydrocarbon-rich natural gases in the western part of the Central European Basin (CEB), accumulations of natural gases from the eastern part of the North German Basin (NGB) are nitrogen-rich with up to 90% N2. This study is focused on the behaviour of fixed ammonium in clay minerals of organic-rich Palaeozoic sediments in the eastern part of the NGB as a major source of nitrogen-rich natural gases. Carboniferous shales have been investigated for a better understanding of nitrogen fixing during diagenesis, storage during burial and release during devolatilization processes or fluid–rock interactions. The total nitrogen contents in the studied Carboniferous shales of the NGB reach up to 2700 ppm with an inorganic fixed portion (in the form of NH4 +–N) of more than 60%. The results of this study indicate an increasing proportion of the mineralogically fixed ammonium with increasing thermal maturity and storage up to catagenetic conditions. The isotopic composition of fixed-NH4 is relatively homogeneous in the majority of the shales and ranges from +1 to +3.5‰. In contrast, samples from the basin centre show a significant decrease in ammonium contents down to 460 ppm coupled with a shift in δ15N up to +5.6‰ suggesting a release of nitrogen on a large scale. Calculation of nitrogen loss and isotopic fractionation indicate that more than 30% of nitrogen was released as ammonium probably as a consequence of fluid-rock interaction with highly saline brines.

Beschreibung: We applied scaled physical analogue experiments to investigate the early development of salt diapirs induced by differential sedimentary loading in an intra-continental basin realm (e.g. the North German Basin). During the experiments, deformation in a salt-analogue viscous layer was initiated by variations in the thickness of an overlying brittle material and subsequent accumulation of the brittle material further sustained deformation. A 2D optical image correlation system was used to monitor the strain evolution in the salt analogue material. Our models indicate that the formation of salt pillow structures can be achieved by minimum variations in the overburden loading. The increase of differential loading by adding synkinematic layers in the subsided areas causes not only an active piercing of the viscous layer through the brittle overburden but also an additional uplift in the adjacent areas. These elevations, named “secondary structures”, act as origins for a successive generation of diapirs. Consequently, an initial perturbation of the salt–sediment-interface can lead to a lateral propagation temporally shifted diapirs. The linkage between primary and secondary structures is reflected in the synkinematic overburden layers such as overlapping peripheral sinks in the transition zone between two diapirs. These sinks, in turn, are a frequently observable phenomenon around salt structures of the North German basin indicating that “secondary diapirism” is an underestimated process – besides regional tectonic stresses – influencing the evolution of salt structures.

Beschreibung: Numerous factors control the topographic evolution of mountain belts. Crustal thickening, rock uplift rate, and denudational forcing doubtlessly interact, but the feedback mechanisms amongst these are disputed, because they operate over entirely different time scales. Cosmogenically-derived denudation rates cover time-scales of 10(3) to 10(5) years, providing a denudational tool that allows us to shed light on interactions between long-term topography-forming processes and short-term factors destroying topography. Prerequisites for the application of this method in presently uplifting and fast-eroding mountain belts like the Central Alps are an investigation of appropriate watershed sizes for systematic sampling. Denudation rates in Maggia tributaries of various sizes reveal that the trunk stream yields statistically the same denudation rate (0.85 ± 0.14 mm/yr) as the tributaries (0.74 ± 0.14 mm/yr). Therefore, sampling of large watersheds is a feasible approach. Denudation rates of watersheds from the Central Alps are amongst the highest ever measured in similar complex settings, ranging in mean from 0.27 ± 0.05 mm/yr for the Alpine foreland to 1.42 ± 0.4 mm/yr for the high crystalline Central Alps. The measured cosmogenic denudation rates are in good agreement with post-LGM lake infill rates; they are significantly higher than recent denudation rates from river loads. We attribute this discrepancy to differences in methodology and integration time scale. We will show that denudation is high in areas of high altitude and high relief. Furthermore, our data shows that denudation rates are low in areas of low rock uplift, and are high in areas of high rock uplift, respectively. It appears that rock uplift and denudation are intimately linked. It follows that either crustal thickening is generating rock uplift; the mountain belt reacts with erosional unloading. Alternatively, high precipitation and glaciers, most pronounced at high altitude, result in high denudation rates at these sites. Topography then would respond by increasing rock uplift.

Beschreibung: Calibration is a fundamental stage of the radiocarbon (14C) dating process if one is to derive meaningful calendar ages from samples’ 14C measurements. For the first time, the IntCal09 calibration curve (Reimer et al. 2009) provided an internationally ratified calibration data set across almost the complete range (0 to 50,000 cal BP) of the 14C timescale. However, only the last 12,550 cal yr of this record are composed of terrestrial data, leaving approximately three quarters of the 14C timescale necessarily calibrated via less secure, marine records (incorporating assumptions pertaining to the temporally variable “marine reservoir effect”). The predominantly annually laminated (varved) sediment profile of Lake Suigetsu, central Japan, offers an ideal opportunity to derive an extended terrestrial record of atmospheric 14C across the entire range of the method, through pairing of 14C measurements of terrestrial plant macrofossil samples (extracted from the sediment) with the independent chronology provided through counting of its annual laminations. This paper presents new data (182 14C determinations) from the upper (largely non-varved) 15 m of the Lake Suigetsu (SG06) sediment strata. These measurements provide evidence of excellent coherence between the Suigetsu 14C data and the IntCal09 calibration curve across the last ~12,000 cal yr (i.e. the portion of IntCal based entirely on terrestrial data). Such agreement demonstrates that terrestrial plant material picked from the Lake Suigetsu sediment provides a reliable archive of atmospheric 14C, and therefore supports the site as being capable of providing a high-resolution extension to the “wholly terrestrial” (i.e. non-reservoir-corrected) calibration curve beyond its present 12,550 cal BP limit.

Beschreibung: Scaled analogue experiments are used to investigate the indentation of two basement blocks into a sedimentary basin and the formation of a fold-and-thrust belt. The experimental set-up has two adjacent indenters moving in parallel with a velocity difference. The slow indenter moves with a relative velocity ranging from 40 to 80% of that of the fast one. In a first experimental series, quartz sand and low-friction glass beads represent the sediment stack and its basal detachment, respectively; silicone oil simulates a viscous detachment in the second series of experiments. The surface evolution and the spatio-temporal strain distribution are derived from particle image velocimetry (PIV). Together with the 3D finite structure derived by cutting the models at the end of each experiment, this allows the analysis of the structural evolution of the experimental wedges. Thrusting wedge development depends crucially on the relative velocity: when the slow indenter moves with a velocity of more than 55% of the fast indenter, a single curved thrust wedge develops. The wedge becomes decoupled along strike-slip zone at large velocity differences, i.e. when the slow indenter moves slower than 55% of the faster indenter. Consequently the thrust front is strongly curved at high (55–60%) and smoothly curved at low velocity differences (70–80%); in all cases curvature increases during indentation. Along the most strongly curved portion of the thrust wedge, the transfer zone rises, particle rotation and material transport oblique to the indentation direction occur directed toward the front of the slow indenter. Thrusting cycles are timed by the fast indenter and influence thrusting in front of the slow indenter. Thrusts nucleate in front of the fast indenter wedge and propagate laterally to the slow indenter front. This implies distant effects of wedge growth active hundreds of kilometres along-strike of orogens. Silicone oil as a detachment induces a low-angle wedge, which is less curved than in the glass beads experiments, and shows variable thrust vergence with fore- and back-thrusts. We compare our experimental results with the curved fold-and-thrust belts of the Tajik basin in front of the Hindu-Kush and Pamir indenters; our results are able to explain several first-order features.