Jens Hornung

Reservoir and aquifer characterization of fluvial architectural elements: Stubensandstein, Upper Triassic, southwest Germany

This paper aims at a quantitative sedimentological and petrophysical characterization of a terminal alluvial plain system exemplified by the Stubensandstein, South German Keuper Basin. The study follows the outcrop-analogue approach, where information derived from outcrops is collected in order to enhance interpretation of comparable subsurface successions. Quantitative data on sandbody geometries, porosities and permeabilities are presented in order to constrain modelling of subsurface sandbodies and permeability barriers. For sedimentological characterization the method of architectural element analysis (Miall, A.D., 1996. The Geology of Fluvial Deposits. Springer, Berlin) was used, and modified to include poroperm facies. A special photo-technique with a precise theodolite survey was developed to create optically corrected photomosaics for outcrop wall maps from up to 20,000 m2 large outcrops. Nine architectural elements have been classified and quantified. Bedload, mixed-load and suspended-load channel fills are separated. The petrophysical characterization of the architectural elements integrated porosity and permeability measurements of core-plugs with gamma-ray measurements along representative sections. It could be demonstrated, that certain architectural elements show a characteristic poroperm facies. Four scales of sedimentary cycles have been recognized in the Stubensandstein. Cyclic sedimentation causes changing lithofacies patterns within the architectural elements, depending on their position in the sedimentary cycle. Stratigraphic position exerts only some, paleogeographic position exerts significant influence on porosity and permeability of the sandbodies. The highest poroperm values were found in proximal areas of the alluvial plain and in middle parts within sedimentary macrocycles. The strong internal heterogeneity on the alluvial plain system is important for its reservoir and aquifer characteristics. Compartments of bedload channel sandstones in medial positions of a stratigraphic cycle represent very good reservoirs or aquifers. The seals or aquicludes are formed by extensive floodplain claystones, lacustrine sediments, paleosols, and suspended-load deposits. Strongly cemented zones of sandstones represent aquitards.

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.

Resources for a growing city - sand extraction north of Belo Horizonte (Brazil)

To integrate essential mass resources for urbanisation into a sustainable land use planning, their amount and location and the consequences of their exploitation have to be analysed beforehand. A multi-temporal case study regarding the sand extraction in a small, exemplary area north of Belo Horizonte has been performed which analyses the dynamic of sand extraction during the last decades and its consequences for environment and land use change. Additionally, the sedimentological architecture of the river system has been studied in an open sand pit to estimate the sand content and the fluvial style of the Quaternary sediments. Based on these case studies, a rough assessment has been made regarding the total sand resources available in this fluvial system. Nevertheless, more detailed studies of the Quaternary sediments are necessary to quantify and locate important sand yielding deposits.

Dreidimensionale Hydrostratigrafie eines Tal-Hang-Aquifers: Kombination von Georadar, Geoelektrik, Bodenkunde und Sedimentologie am Beispiel des Seebachs, Nordschwarzwald Three-dimensional hydrostratigraphy of a hillslope valley aquifer: combination of GPR, geoelectrics, pedology and sedimentology using the example of the Seebach, northern Black Forest

Filtering and storage of precipitation, runoff, and subsequent groundwater recharge is governed by the structure and properties of the shallow subsurface and the soils formed therein. Hence, detailed knowledge about the three-dimensional structure, thickness and composition of the shallow subsurface is essential to quantify these processes; special benefit can be derived in connection with the hydraulic and material-specific properties. Geobodies can be mapped by complementary, non-invasive, geophysical methods. Associated with lithofacies, geophysical and other properties these “geobodies” can be fingerprinted. A 3D model containing e.g. porosity, field capacity, permeability, grain size and soil chemistry can be build. Geoelectrical resistance tomography and three-dimensional (3D) ground-penetrating radar surveys have been carried out in the catchment of the “Seebach” (Forbach, Bunter, Black Forest, Southern Germany). A test field was established and investigated with respect to the sedimentological and pedological architecture of the shallow subsurface, going along with lithofacies mapping, granulometry, and permeability investigations. The synthesis of all data resulted in a three-dimensional quantitative subsurface model of the shallow subsurface architecture. Together with the associated hydrological characteristics, this can serve as input parameters for water budget and sorption models.