A. Siehl

Minette-type ironstones

Summary Oolitic ironstones occur in various sedimentary environments: shallow marine to deltaic, lacustrine, fluviatile and pedogenic. Distinction between formational and depositional environment is not always possible. Most of the marine and fluvial minette-type ironstones consist of reworked ferruginous coated grains deposited in agitated water, but there exist also indicative structural features of in situ formation in the supporting medium of lateritic and hydromorphic environments. In the zone of oscillating groundwater repeated leaching and subsequent concretionary precipitation of hydrated ferric oxides take place, according to the prevailing Eh/pH-conditions and microbial activity. The moderate Al substitution of goethite from hydromorphic environments corresponds to the observed range in oolitic ironstones. The authors therefore assume erosion, reworking and subsequent fluviomarine redeposition of soil derived ooids to be the major processes of generating minette-type ironstones. Postdepositional diagenetic changes may convert the aluminous, silica-rich ferric oxides into berthierine in reducing environments if the chemical bulk composition of the primary goethite is similar. Since any aquatic milieu with appropriate fluctuations of Eh and pH can produce ferruginous coated grains, marine iron ooids associated with hardgrounds and areas of low sediment input can also occur. But there, release of ferrous iron, transport in saline interstitial waters and fixation of ferric hydroxides — usually with very low Al-substitution — take place in a much smaller scale, unable of generating the huge iron accumulations of minette-type ore deposits.

Classification and mapping of radon-affected areas in Germany

Abstract The geology-based approach has proven to be a powerful tool for predicting radon prone areas in Germany. Soil-gas radon measurements in conjunction with geological and soil investigations in representative test areas are the basis for classification and regionalization of the geologically induced risk of high indoor radon values. Radon production and radon supply are the essential criteria for the radon potential. Because of their complex and still not well-understood functional interrelationships, an empirical ranking classification is presented, based on radon concentration in soil gas and gas permeability. To ensure comparability, a standardized procedure for radon and permeabilitiy measurements was developed. Of great importance is the discrimination between geochemically induced and structurally controlled radon. Areas with low radionuclide background levels in soils and rocks may exhibit significant radon anomalies at local geochemical traps and along faults and fracture zones.

The Story of the GeoToolKit—An Object-Oriented Geodatabase Kernel System

The quickly increasing number of spatio-temporal applications in fields like environmental monitoring, geology and mobile communication is a new challenge to the development of geodatabases. However, the query functionality of todays geo-information systems is still limited to the thematic attributes of spatial objects and to spatial 2-D objects. This article reports on GeoToolKit, an object-oriented geo-database kernel system developed at Bonn University to support 3-D/4-D geological applications. GeoToolKit is not a GIS-in-a-box package, but rather a library of C ++ classes that allows the incorporation of spatio-temporal functionality within an application. Being a component toolkit, it encourages the development and deployment of re-usable and open software. The history, concepts and implementation of GeoToolKit are discussed in detail. Performance tests underline the practicability of the concepts. Extensions to and experiences with GeoToolKit applications like GeoStore, GeoWeb and WellStore are presented. Finally, we give an outlook on our future research introducing GeoToolKit as a 3-D/4-D database component within a network of distributed and mobile geo-information services.

First steps towards an interoperable GIS — an example from Southern Lower Saxony —☆

Abstract In geosciences the necessity of combining geological and geophysical information as well as applying tools for designing 3D geological and geophysical models is well accepted. Nevertheless, in most cases this demand is only put into practice by file transfer between the applications. The creation of a common 3D model is complicated by the inflexible handling of new and reinterpreted data and by changing applications, heterogeneous operating systems and/or hardware platforms. We present a new approach for a component based GIS which is coupled with an object oriented database management system. The original data, as well as the derived data and the 3D models, are stored in the extensible database. Geological and geophysical 3D modeling tools have direct access to the database via the Common Object Request Broker Architecture (COREA). By this means, we obtained both the integration of the software components and independence from changing software applications and changing platforms, finally resulting in an interoperable 3D GIS.

Space-time modelling of the Lower Rhine Basin supported by an object-oriented database

Abstract Within the framework of the Collaborative Research Centre (CRC, SFB 350) at Bonn University, dealing with interacting geological processes in continental regimes, a joint 3D/4D GIS project is developed by geologists and computer scientists. When analysing and modelling the structural and sedimentary evolution of the Cenozoic intracratonic Lower Rhine Basin in NW Germany, the need emerged to combine methods and tools of space-time modelling of geologically defined geometries with advanced database management techniques. Computer aided geological design typically requires operations for storage and retrieval of large 3D data sets together with their attributes and topological relations and for the generation of model surfaces of stratigraphic boundaries and faults, which in turn define the boundaries of geological bodies developing in time. The requirements of interactive visualisation, analysis and modification of complex and time dependent geometries entail the demand for spatial, topological and time-related database queries as well as for various consistency and integrity tests. Considering these specific geological requirements, an object-oriented geo-database kernel system has been designed and implemented as a “GeoToolKit” for 3D/4D geoscience applications.

Kinematic subsidence modelling of the Lower Rhine Basin

Kinematic geological models can greatly enhance our understanding of the interaction and timing of processes involved in the formation of sedimentary basins. The prototype tool for the calculation and visualisation of such models presented here is aimed at studying subsidence rates and patterns at basin scale: A backstripping algorithm is applied to a geometrical 3Dmodel consisting of prismatic volumes, constructed from an initial set of stacked triangulated surfaces. As a result, we obtain a collection of palinspastically restored volumes for each timestep of basin evolution. The backstripped volumes of each layer are then arranged within a timescene, and the set of timescenes collected as a hierarchical timetree. By interpolating between succeeding key-frames, the subsidence history of the basin can be viewed as an interactive, continuous animation. The approach is illustrated using a high-resolution dataset from the German part of the Cenozoic Lower Rhine Basin.

Towards a balanced 3D kinematic model of a faulted domain - the Bergheim open pit mine, Lower Rhine Basin

In the context of the investigation of the sedimentary and structural evolution of the Cenozoic Lower Rhine Basin, the construction of a volume-balanced kinematic model of a small faulted domain with detailed spatial information on strata and fault geometry from a set of parallel geological sections is under development. A 3D geometry model is built that allows for relative movements of blocks at fault surfaces. Rouby’s method of restoration in the map plane is used to determine horizontal displacement fields. The 3D and 3D(t) geometry models are supported by the object-oriented geometry database tool GeoToolKit for storage and retrieval of selected parts of the model using queries referring to spatial and temporal criteria, while visualization is based on key frame technique.

Sedimentation in the Atlas Gulf I: Lower Cretaceous Clastics

The transgressions and regressions in the Atlas Gulf control the facies of the clastic deposits during the Early Cretaceous. As the coastline oscillates, the succession of varied environments migrates systematically landward and seaward. Large terrigenous supply is characteristic of regressive periods (Upper Hauterivian, Lower Aptian) and small supply of transgressive periods (Valanginian, Barremian, Upper Aptian). The distributive province of the terrigenous detritus in the eastern hinterland of the gulf (e.g., the Precambrian crystalline massifs of the Central High Atlas) remains constant. The clastics, transported westward through the Atlas Basin and decreasing in grain size, reach the continental slope and are deposited as turbidites in the contemporaneous offshore sediments in DSDP Site 370/416. The following sedimentological and petrographical parameters were used for the analysis of the paleogeographical and paleoenvironmental development: The directional distribution of cross bedding and sole marks, the feldspar content, the regional distribution of the main constituents (insoluble residue, calcite, and dolomite), the calcium content of the dolomites, the change of the sediment thickness, and the occurrence of corals and redbeds.

Radon transfer from ground to houses and prediction of indoor radon in Germany based on geological information

Publisher Summary Soil gas radon concentrations of distinct geological units in Germany are compared with assigned indoor radon measurements in several test areas with different geological settings. A set of transfer factors for specific situations depending on geology and dwelling characteristics was derived that enable the prediction of the percentage of houses exceeding reference indoor radon levels. To validate the geology-based area prediction, the soil gas database of a generalized German radon map was matched with about 18 000 long-term indoor radon measurements grouped into administrative units on a district level. For most of the districts, prognosis and measurements are in acceptable agreement, and a clear distinction between areas with enhanced radon both in soil gas and in dwellings versus areas with low radon characteristics can be made.

Structural setting and evolution of the Afghan orogenic segment – a review

Abstract The actual state of knowledge concerning the tectonic evolution of the Afghan orogenic segment is summarized in the context of the neighbouring regions. The segment can be divided into: (1) the Late Palaeozoic North Afghan Variscan domain, which forms the southern margin of the Turan Plate; (2) the Early Cimmerian (Late Triassic–Early Jurassic) Palaeotethys suture zone of Middle Afghanistan, with the associated magmatic arc and back-arc rift extending from the Parapamisos and western Hindu Kush to the northern Pamir Mountains; (3) the Late Cimmerian (Late Jurassic–Early Cretaceous) domain of the Central Afghan Block mosaic with Gondwana-derived terranes; and (4) the Cenozoic-age Himalayan domain, which fringes the Cimmerian domain along the transpressive boundary of the Indian Plate in the east and the accretionary complex of the Makran subduction zone in the south. This current review of the scattered literature of a country where geological fieldwork effectively ceased 35 years ago is intended to bridge the gap between the better-known regions to the west in eastern Iran, and to the east in the Pamir–Punjab syntaxis.