Matthias Hinderer

Late Quaternary denudation of the Alps, valley and lake fillings and modern river loads

AbstractErosional denudation of the Alps and their role as sediment source underwent major changes throughout the Quaternary, by repeated glaciation and deglaciation. The sediment fluxes of 16 major Alpine drainage basins were quantified by determining the sediment volumes which have been trapped in valleys and lake basins. These became sedimentologically closed after the last glacier retreat around 17 000 cal. BP. The sediment volumes distributed over their provenance areas yield mean mechanical denudation rates between 250 to 1060 mm ka−1. In contrast, modem denudation rates, derived from river loads and delta surveys, range from 30 to 360 mm ka−1. Relief, such as mean elevation and slope, turned out to be the primary control of both modem and Late Glacial mechanical denudation. Rock types seem to be responsible for scatter of the data, but their role is masked by other factors. Modern denudation rates increase with higher proportions of bare rocks and glaciated area, but decrease with forest cover. An ...

Atmospheric carbon burial in modern lake basins and its significance for the global carbon budget

Abstract Lake basins (∼2.7×10 6 km 2 , about 0.8% of the ocean surface or 2% of the land surface) bury a surprisingly high amount of atmospheric carbon (∼70×10 6 t/a) which reaches more than one fourth of the annual atmospheric carbon burial in the modern oceans. This is mainly accomplished by the rapid accumulation of lacustrine sediments and a very high preservation factor (on average 50 times higher than that in the oceans). Lakes with relatively large drainage areas commonly display the highest carbon accumulation rates. In most cases, burial of organic matter is more important than that of carbonate carbon produced by silicate weathering, in contrast to the oceans where the burial of atmospheric carbonate carbon almost reaches the same amount as that of organic carbon. Exceptions to this rule are closed lake basins in arid to semiarid climate which precipitate a major part of their atmosphere-derived dissolved inorganic carbon (DIC) as carbonate. These results are demonstrated in some detail for L. Qinghai, China, (low contribution of atmospheric carbonate carbon) and L. Turkana, East Africa, (high contribution from silicate rocks). Further data are gained by estimates for a number of closed and open lakes. The drainage areas of the lakes withdraw atmospheric carbon at rates of mostly 1–4 g/m 2 /a, calculated from the lacustrine carbon burial. Carbon burial rates in lakes commonly increase with change to wetter and warmer climate (partially larger lake surfaces, higher rates of seasonal carbonate precipitation, trend to stratified lake waters with oxygen-deficient bottom water). Anthropogenic influence mostly enhances the production and preservation of organic carbon in lake basins (often by a factor of 3–4). After the last glacial maximum, the joint action of the globally spreading vegetation, peat growth, and carbon burial in lakes would have been able to reduce the atmospheric carbon pool to one third to one half of its present amount within a time period of 1 ka. However, CO 2 exchange between the atmosphere and the ocean has brought about an overall increase in the atmospheric CO 2 during the Holocene. The contribution of lakes and artificial reservoirs in counteracting man-made CO 2 emissions should not be neglected.

Geochemical evolution of closed-basin lakes : general model and application to lakes Qinghai and Turkana

In contrast to most previous models for the evolution of closed-basin lakes, we present an integrated model which considers various water budget patterns, clay regradation, SO4 reduction and subbottom leakage in addition to the classical equilibrium approach of mineral precipitation. The model was applied to Lakes Qinghai and Turkana, which significantly differ in the lithologies of their drainage areas but are representative of the carbonate-rich sedimentary rock province of the Tibet–Qinghai Plateau and the silicate rock province of Eastern Africa. Both lakes are now topographically closed, but to some degree hydrologically open (subbottom leakage). Major results of the mode calculations show that: the lithology controls the ultimate brine which is of Na–(K)–Cl-type for Qinghai Lake and of Na–HCO3–Cl-type for Lake Turkana. SO4 reduction delays the onset of sulfatic mineral precipitation and favours the formation of Na–carbonates such as trona at the expense of calcite. Clay mineral regradation plays an important role before the saturation of sulfatic or chlorine minerals is reached. In particular, magnesite formation may be in competition with Mg-bearing clay minerals. Finally, simulations with various hydrological scenarios have shown that the modern hydrochemistry of both lakes cannot be reproduced by simply evaporating inflow water, but reflects long-term accumulation and evolution of solutes by continuous inflow over several thousand years. The diversity of lake water composition within a uniform lithological province can thus be largely ascribed to varying hydrological conditions.

The world's large lake basins as denudation-accumulation systems and implications for their lifetimes

The mechanical denudation rates of 81 large lake basins (lake area > 500 km2) were determined from long-term river loads and erosion maps. Using the drainage area/lake area ratios the mean sedimentation rates of the lakes were calculated for a porosity of 0.3. The mean sedimentation rates of different lake types vary between 0.1 mm/a (glacial lakes, lowland) and 5.4 mm/a (mostly sag basin lakes). The calculated lifetimes of the lakes are based on the lake volumes and mean sedimentation rates, assuming steady-state conditions and solely clastic material. On average, glacial lakes in highlands and fault-related lakes show the shortest lifetimes (c. 70 ka), glacial lakes in lowlands and rift lakes have the longest lifetimes (c. 1 Ma). Some lakes remain unfilled for very long time spans due to rapid subsidence of their basin floors. The calculated lifetimes are compared with those derived from sediment core studies. Most core studies indicate lower mechanical sedimentation rates than the calculated ones because a major part of the incoming sediment is trapped in deltas. However, a number of lakes (e.g., the Great Lakes of North America) show the opposite tendency which is largely caused by extensive shoreline erosion and resuspension. The lifetimes of large glacial lakes often exceed the duration of interglacials. Hence, their lifetimes are restricted by glaciation and not by sediment infill. Rift lakes persist for long time periods which exceed the calculated lifetimes in some cases. Time-dependent subsidence, basin extension, as well as the impact of climate change are briefly described.

A GIS-based method to calculate flow accumulation by considering dams and their specific operation time

This paper presents a new approach to calculate flow accumulation with geographic information systems (GIS). It is based on the well-known D8 single-flow algorithm that is extended to consider the trap-efficiencies of dams and their specific operation time. This allows realistic calculations of flow accumulation for any time period. The new approach is not restricted to surface water runoff but can be applied to all kinds of mass fluxes like suspended or dissolved sediment load (weighted flow accumulation). To facilitate its use, two GIS extensions for ArcView and ArcGIS have been developed. This paper presents the principles of the new approach, the functionality of the extensions and gives some applications in the fields of hydrology and sedimentology.

Accumulation of polycyclic aromatic hydrocarbons in rural soils based on mass balances at the catchment scale.

Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic pollutants that are ubiquitously distributed in the environment at relatively high concentrations. In our study we investigated the long-term fate of atmospheric PAHs in soils of rural areas, resulting from diffuse pollution based on mass balances at the catchment scale. By determining PAHs in several environmental compartments, estimates of soil storages and water fluxes were made and compared with atmospheric deposition. The results indicate that more than 90% of the incoming PAHs remain in the catchments and accumulate in the topsoils. Furthermore, revolatilization of PAHs from soils and degradation in the soils is very limited, resulting in ongoing accumulation in topsoils, in particular for low-volatile PAHs. Combustion-derived carbonaceous particles were detected in atmospheric deposition as well as in the soil samples. Since these particles are very strong adsorbents, they are suspected to play a key role in the environmental fate of the diffuse distributed PAHs.

Palaeozoic glacial depositional environments of SW Saudi Arabia: process and product

Abstract Saudi Arabia is one of the few places in Gondwana where deposits of two Palaeozoic glaciations are well preserved. They were formed under similar conditions in a tectonically stable shelf setting. We studied the sedimentary facies and architectural geometries of Upper Ordovician and Permo-Carboniferous glaciogenic deposits in the Wajid Sandstone and developed a genetic model for both units. Common features and of both glacial episodes are (a) incision of glacial (tunnel?) valleys, (b) subsequent valley fill by proglacial deposits in front of an oscillating, polythermal ice shield; (c) intra-formational erosional events through repeated ice advance, (d) widespread and large-scale soft deformation due to glacial surge during deglaciation, and (e) marine transgression most probably due to eustatic sea-level rise following deglaciation. The general patterns and observations fit well with recently published observations on Upper Ordovician deposits in northern Africa, pointing to closely coupled glaciological processes of the North African–Arabian ice shield. Although the same general patterns apply for the Permo-Carboniferous glaciation, sedimentary styles and petrographical properties differ, probably due to a more heterogeneous ice-flow pattern controlled by a more pronounced topography after the Hercynian tectonic event.

Comparing trends in lake acidification using hydrochemical modelling and paleolimnology : The case of the Herrenwieser See, Black Forest, Germany

We reconstruct the post-industrial acidification of a dystrophic headwater lake in the Black Forest by (1) modelling past chemical change using MAGIC and (2) assessing past pH using diatoms from a sediment core. Both methods were consistent in indicating only a small pH decline between the mid 19th century and the 1980s, followed by a minor recovery around 10 years after peak sulphate deposition. However, the magnitude and timing of pH change varied between the different diatom algorithms (weighted averaging vs. multiple regression, maximum change 0.21 and 0.78 pH units, respectively), and between the most extreme diatom scenario and MAGIC (0.15 pH units). We advocate further validation exercises of this type to assess whether consistency is maintained or differences emphasised, where pH change has been larger.

Petrography and geochemistry of Palaeozoic quartz-rich sandstones from Saudi Arabia: implications for provenance and chemostratigraphy

The Arabian Peninsula hosts a thick Palaeozoic succession, ranging from the Cambrian through the Permian. It not only contains deposits of the two major Palaeozoic glaciations but also holds both the major Palaeozoic hydrocarbon source and reservoir rocks. In addition, Palaeozoic sandstones serve as important aquifers. The succession is dominated by highly mature quartz arenites, as seen in thin sections. It is starved of fossils and very uniform in lithology. In order to better understand provenance, tectonic setting and stratigraphic relationships, the petrography as well as major and trace element geochemistry of sandstones were studied. Samples were taken from two study areas in southern (Wajid area) as well as central and northern (Tabuk area) Saudi Arabia. The dataset we present here is the first comprehensive study to cover the entire Palaeozoic succession in both the southern and northern part of the Arabian Peninsula. The collisional signal from some samples is a relic from the last stages of the amalgamation of Gondwana, carried into the basin by glaciogenic sediments. Major and trace element geochemistry indicate the Neoproterozoic basement of the nearby Arabian Shield as the most likely source for the detritus. Tectonic discrimination diagrams suggest that deposition of sandstones took place in an intracratonic setting, which is in accordance with the established model for the evolution of the Arabian Plate. An influx of fresh material, probably sourced from the Shield, did occur in the late Palaeozoic units of the Wajid area but did not reach the Tabuk area. Geochemical methods have shown some success in characterising the provenance of both study areas but were unable to reliably assess sedimentary recycling. A (meta-)sedimentary source for the Palaeozoic sandstones could therefore neither be proven nor refuted. Multivariate cluster and principal component analysis of geochemical data revealed significant differences between the two study areas.

Dielectric mittivity of logic Materials at different er contents - Measurements with an impedance analyzer

Dielectric permittivity is an important parameter for all investigations based on electromagnetic waves (e.g. GPR and TDR measurements). In combination with the electric conductivity, it is crucial for the determination of the propagation velocity, the reflection coefficient and the decay of the electromagnetic wave. The dielectric permittivity depends on several factors like water content, mineralogy, grain size, and bulk density of the material. Our laboratory measurements of dielectric permittivity show quantitative relations between these parameters and that commonly used general algorithms for moisture detection bear significant inaccuracies (up to 200% error for clay substrates). Therefore, it is crucial to determine the permittivity for every specific application. This paper provides new algorithms for some most important substrate types, which can be used to recalibrate TDR-tools for specific applications. However, measurements of the dielectric permittivity are also frequency-dependent. In this study an impedance analyzer was used, which provides a frequency range between 10MHz and 1GHz. This is inside the most common range of applications like the TDR measurement method, which has a frequency range from 20KHz up to 20GHz. Ground penetrating radar measurements operate mostly in a frequency range from 40 to 900MHz.