Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy

Abstract

The approach of 'dynamic stratigraphy' aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales. This approach was used to investigate Quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties. Facies analysis within 62 gravel pits, laboratory permeability measurements of field samples and geophysical surveys (3-D georadar, 2-D seismic reflection) led to the detection and classification of sedimentary heterogeneity according to the following six scales whereby each scale can be translated into defined hydrostratigraphic units. (1) Particles and pores (micro scale) that reflect depositional and diagenetic fluid dynamics as well as source material behaviour (e.g. grainsize, roundness, lithological composition). This was found to be important for the hydrogeochemistry of groundwater in gravel aquifers (e.g. higher sorption capacity of carbonrich limestone particles for organic pollutants). (2) Strata (meso scale) contain the recognition of sorting, fabric, texture and stratinomic features, which can give an indication of transport and depositional dynamics. Five major lithofacies groups, for example, were distinguished within fluvial gravel-bed deposits. Their variable hydraulic properties led to their subdivision into 12 hydrofacies types. They form the smallest mappable hydrostratigraphic units, which may result in either preferred pathways for fluid flow or flow barriers. (3) Depositional elements (macro scale) enable reconstruction of sedimentary/geomorphic elements and their dynamics within a depositional system (e.g. gravel-bed braided river systems are dominated by gravel sheet, gravel dunes and scour pool depositional elements). Hydrostratigraphically, the architecture of depositional elements influences the hydraulic connectivity and local permeability structure/distribution within an aquifer body.Five types of depositional elements in fluvial gravel-bed deposits were distinguished and their geometries/dimensions quantified. (4) Facies bodies (mega scale) composed of a stack of depositional elements and strata recording distinct environmental systems and their dynamics (e.g. a coarse-grained prograding delta system). Hydrostratigraphically, facies bodies represent major compartments of an aquifer. Six major types of meltwater-controlled facies bodies were identified in the study area. (5) Genetic sequences (mega scale) reflect the shifts of depositional environments caused by allocyclic changes (e.g. glacial advance recorded by a coarsening upward sequence) or autocyclic changes of landscape shaping events. These sequences may form separate hydrostratigraphic units or aquifer storeys. (6) Basin fill (giga scale) comprising the lateral and vertical stacking of facies bodies and genetic sequences controlled by either long-term glacier dynamics or short term flood events. The regional distribution of permeable gravel units and, for example, less permea...

Three-dimensional high resolution fluvio-glacial aquifer analog: Part 1: Field study

“…The classification into small-dimensional sedimentological units is, for the most part, based on the classification used by Keller (1996) and Heinz and Aigner (2003b). According to this system, it is possible to differentiate between typical lithofacies types that can be characterized by the spectrum of grain sizes, the sorting, level of roundness, and the composition of the particles, as well as the structure and the layering.…”

“…-poorly sorted gravel (Gcm): gravel with a broad grain size distribution, cobbles and also sand as secondary components; the layered appearance is due to changing sand content, but imbrication of particles indicates horizontal-to cross-bedding; this litho-and hydrofacies originates from bedloads of high-energetic flood events (Klingbeil et al, 1999;Heinz et al, 2003b); it can be of significant lateral extension up to hundreds of meters and as such form accretionary elements (Fig. 2a).…”

“…The Herten gravel body is part of the main discharge area, including high-energetic depositions of coarse sediments. In the following, the genetic classification and sedimentological interpretation will only be tangent and the reader is referred to Heinz and Aigner (2003b) and Kostic et al (2005) for more details.…”

“…Among others, Siegenthaler and Huggenberger (1993), Beres et al (1995), Heinz and Aigner (2003b) and Heinz et al (2003) intensively studied the pro-glacial environment along the river Rhine. They interpreted their observations from multiple outcrop studies with respect to depositional conditions and presented regional facies models that can be distinguished according to discharge types (main, intermediate, minor discharge area) of the former glacier outwash plain.…”

Aquifer configuration and geostructural links control the groundwater quality in thin-bedded carbonate–siliciclastic alternations of the Hainich CZE, central Germany

“…The spatial correlation of marlstones presumes that basin-centre marlstones are laterally more continuous than shallow water limestones (Aigner, 1985). In accordance with published examples for multi-storey subsurface architecture (Haag and Kaupenjohann, 2001;Heinz and Aigner, 2003;Klimchouk, 2005;Sharp, 2007), we use the term "aquifer storey" to emphasize our conceptualization of the fine-stratified setting by arbitrary definition of intervals that are dominated by fractured limestone beds and confined at the top and base by unfractured or low permeable beds, the latter with an effective minimum thickness of 80 cm. The degree of aggregation is a compromise between increased detail to account for different hydrogeochemical patterns and the necessary well yield for recovering water samples.…”