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: 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: 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: 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: 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: The Aral Sea Basin is a critical area for studying the influence of climate and anthropogenic impact on the development of hydrographic conditions in an endorheic basin. We present organic-walled dinoflagellate cyst analyses with a sampling resolution of 15 to 20 years from a core retrieved at Chernyshov Bay in the NW Large Aral Sea (Kazakhstan). Cysts are present throughout, but species richness is low (seven taxa). The dominant morphotypes are Lingulodinium machaerophorum with varied process length and Impagidinium caspienense, a species recently described from the Caspian Sea. Subordinate species are Caspidinium rugosum, Romanodinium areolatum, Spiniferites cruciformis, cysts of Pentapharsodinium dalei, and round brownish protoperidiniacean cysts. The chlorococcalean algae Botryococcus and Pediastrum are taken to represent freshwater inflow into the Aral Sea. The data are used to reconstruct salinity as expressed in lake level changes during the past 2000 years. We quantify and date for the first time prominent salinity variations from the northern part of the Large Aral Sea. During high lake levels, I. caspienense, representing brackish conditions with salinities of about 10–15 g kg− 1 or less, prevails. Assemblages dominated by L. machaerophorum document lake lowstands during approximately 0–425 AD (or 100? BC–425 AD), 920–1230 AD, 1500 AD, 1600–1650 AD, 1800 AD and since the 1960s. Because salinity in the Aral Sea is mostly controlled by meltwater discharges from the Syr Darya and Amu Darya rivers, we interpret changes in salinity levels as a proxy for temperature fluctuations in the Tien Shan Mountains that control snow melt. Significant erosion of marine Palaeogene and Neogene deposits in the hinterland, evidenced between 1230 AD and 1400 AD, is regarded as sheet-wash from shore. This is controlled by the low pressure system that develops over the Eastern Mediterranean and brings moist air to the Middle East and Central Asia during late spring and summer. We propose that the recorded environmental changes are related primarily to climate, but perhaps to a lesser extent by human-controlled irrigation activities. Our results documenting climate change in western Central Asia are fairly consistent with reports elsewhere from Central Asia.

Beschreibung: Two of the Earth´s largest geophysical anomalies, the Beattie Magnetic Anomaly (BMA) and the Southern Cape Conductive Belt (SCCB) extend across the southern African continent for more than 1000 km in an east-west direction. Based on previous electrical and magnetometer array measurements it is believed that both anomalies have a common crustal source with a width of 50 km represented by serpentinized palaeo-oceanic srust. New two-dimensional (2D) electrical conductivity models along a profile from Prince Albert to Fraserburg outline a narrow (2 km wide), southward-dipping zone of high electrical conductivity in the upper crust below the centre of the Beattie Magnetic Anomaly (BMA). Two-dimensional modeling studies of areo-magnetic data show that simple models that can explain the magnetic signature of the BMA, are not consistent with a narrow conductivity anomaly. Thus a common source for the two anomalies is unlikely. A second magnetotelluric (MT) experiment across the BMA, conducted along a 75 km profile centred on Jansenville, 350 km east of the first profile, resolves a sub-vertical and narrow condutivity anomaly below the centre of the BMA. At this location the conductor is reaching deeper to lower crustal levels and is inclined towards the north.

Beschreibung: 〈P〉The speciation of boron in H〈FONT SIZE="-1"〉2〈/FONT〉O+H〈FONT SIZE="-1"〉3〈/FONT〉BO〈FONT SIZE="-1"〉3〈/FONT〉±NaCl and H〈FONT SIZE="-1"〉2〈/FONT〉O+Na〈FONT SIZE="-1"〉2〈/FONT〉B〈FONT SIZE="-1"〉4〈/FONT〉O〈FONT SIZE="-1"〉7〈/FONT〉 fluids was studied in situ at temperatures between 22 and 600°C and pressures from 0.1 MPa to about 2 GPa using Raman spectroscopy and a hydrothermal diamond anvil cell. Additionally, we determined the frequency shifts of the 877 cm〈SUP〉-1〈/SUP〉 Raman line of [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 in aqueous fluids with temperature (〈FONT FACE="Math1"〉d〈/FONT〉〈FONT FACE="Math5"〉v〈/FONT〉〈FONT SIZE="-1"〉877〈/FONT〉/〈FONT FACE="Math1"〉dT〈/FONT〉)〈FONT SIZE="-1"〉P=0.1 MPa〈/FONT〉 = -0.02532 cm〈SUP〉-1〈/SUP〉K〈SUP〉-1〈/SUP〉 and pressure (〈FONT FACE="Math1"〉d〈/FONT〉〈FONT FACE="Math5"〉v〈/FONT〉〈FONT SIZE="-1"〉877〈/FONT〉/〈FONT FACE="Math1"〉d〈/FONT〉P)〈FONT SIZE="-1"〉T=22°C〈/FONT〉 = 4.06 cm〈SUP〉-1〈/SUP〉GPa〈SUP〉-1〈/SUP〉. The observed species in acidic fluids were [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 and smaller amounts of a four-coordinated boron species which may be attributed to dissolved metaboric acid HBO〈FONT SIZE="-1"〉2〈/FONT〉(aq). The ratio of this B〈SUP〉[4]〈/SUP〉-O species to [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 increases with temperature and decreases slightly with addition of NaCl. In alkaline solutions, polyboric ions depolymerize rapidly with temperature. Thus, [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 and [B(OH)〈FONT SIZE="-1"〉4〈/FONT〉]〈SUP〉-〈/SUP〉 were the only remaining detectable species at 500 and 600°C. The Raman spectra showed an increase of [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 relative to [B(OH)〈FONT SIZE="-1"〉4〈/FONT〉]〈SUP〉-〈/SUP〉 with temperature and an increase of [B(OH)〈FONT SIZE="-1"〉4〈/FONT〉]〈SUP〉-〈/SUP〉 relative to [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 with pressure. 〈BR〉 The general trend in the boron speciation is a higher stability of simpler complexes with temperature. The experimental observations strongly indicate that planar three-coordinated [B(OH)〈FONT SIZE="-1"〉3〈/FONT〉]〈SUP〉0〈/SUP〉 is the predominant boron species in the aqueous phase over a wide range of P-T-pH conditions. This supports the validity of previous assumptions on boron coordination in crustal and mantle wedge fluids.〈BR〉 〈/P〉

Beschreibung: Earth's long-term sea-level history is characterized by widespread continental flooding in the Cretaceous period (~145 to 65 million years ago), followed by gradual regression of inland seas. However, published estimates of the Late Cretaceous sea-level high differ by half an order of magnitude, from ~40 to ~250 meters above the present level. The low estimate is based on the stratigraphy of the New Jersey margin. By assimilating marine geophysical data into reconstructions of ancient ocean basins, we model a Late Cretaceous sea level that is 170 (85 to 270) meters higher than it is today. We use a mantle convection model to suggest that New Jersey subsided by 105 to 180 meters in the past 70 million years because of North America's westward passage over the subducted Farallon plate. This mechanism reconciles New Jersey margin–based sea-level estimates with ocean basin reconstructions.