Data di Pubblicazione:
2013
Citazione:
Modelling the hydrostratigraphic heterogeneity of a glacio-fluvial scour-pool / R. Bersezio, L. Pessina, L. Cattaneo, E. Cavalli, F. Felletti, M. Giudici, M. Mele - In: 10th International Conference on Fluvial Sedimentology. Conference programme and Abstracts Volume / [a cura di] D.R. Parsons, P.J. Ashworth, J.L. Best, C.J. Simpson. - Leeds : University of Leeds, 2013. - ISBN 978-1-905593-92-7. - pp. 66-67 (( Intervento presentato al 10. convegno International Conference on Fluvial Sedimentology (ICFS 10) tenutosi a Leeds nel 2013.
Abstract:
Modelling the hydrostratigraphic heterogeneity of a glacio-fluvial scour-pool
R. Bersezio1, L. Pessina1, L. Cattaneo2, E. Cavalli1,3, F. Felletti1, M. Giudici2 and M. Mele1
1 Dipartimento Scienze della Terra Università di Milano, via Mangiagalli 34, Milano, ITALIA. riccardo.bersezio@unimi.it
2 Dipartimento Scienze della Terra Università di Milano, via Cicognara 7, Milano. mauro.giudici@unimi.it
3 Now at: CAP Holding., Assago (Milano), ITALIA. emmanuele.cavalli@capholding.it
1. Rationale, aims and methods
Realistic representations of the sedimentary heterogeneity of alluvial aquifers are necessary to solve flow and transport problems. The improvements of mathematical tools to simulate the heterogeneity distribution in these sediments permit to handle 3D fields at fine scales. At this purpose, the textural and geometrical components of sedimentary heterogeneity must be reproduced efficiently. Nevertheless, the current mathematical methods are still far from yielding satisfactory results concerning complex geometries and (hydro)-facies distributions (i.e. textures, structures and the related porosity/permeability properties). This is the case of alluvial aquifers that are characterized by: i) complex curve and oblique geometries of the sedimentary bodies bounded by complex truncation surfaces, ii) highly variable and non-stationary facies associations and iii) hierarchic nesting of sedimentary units with contrasting permeability (scour pools, accreting bars, channel fills, terraced valleys and flood plains). Modeling this complexity in the real subsurface aquifer stratigraphy is difficult when fine-scale models are required. The study of exposed aquifer analogues permits to try and improve the geostatistical techniques for simulation of aquifer stratigraphy (pixel or object based methods), using complete sedimentological data-sets. Some recent examples of detailed geometric, sedimentological and geophysical descriptions of different 3-D alluvial aquifer analogue architectures led to reliable mathematical simulations (Zappa et al., 2006; Felletti et al., 2007; Dell’arciprete et al., 2010; Bayer et al., 2011; Comunian et al., 2011). Aiming to combine the best possible reproduction of complex geometries with the accurate simulation of the textural distribution, we investigated an aquifer analogue including the gravel-sand multi-storey fill of a small scour pool. The descriptive approach included the sedimentological, geophysical and petrophysical analyses that yielded a quasi-3-D quantitative model of the analogue. After geostatistical simulation we applied flow and transport models to investigate the behavior of the numerical 3-D “virtual aquifer”.
2. Results
The real analogue is a sediment block (7 m 4 m 1.5 m) dug into a gravel-sand quarry that is open into the Upper Pleistocene sandur of the Verbano glacier amphitheater (eastern Piedmont, Northern Italy). The block shows the complex network of cross-cutting, small-scale trough-fills (curve and planar cross-bedded gravels, sandy gravels and sands) filling a scour-pool cut into very fine sand and silt. The complexity of this setting includes also deformation structures due to undermining and failure of the fine-grained pool banks, with gravel fills pinched in between the projecting limbs of the deformed silty-sands. The preliminary geophysical investigation and the subsequent dissection of the block (progressive removal of 50 50 50 cm sediment “voxels”) permitted full inspection of the scour-pool volume. So that, the final descriptive data-set and the sedimentological model include: geo-electrical (VES – ERGI) and GPR images of the block; sedimentological logs, photomosaics and facies maps at cm-scale accuracy along vertical and horizon
Tipologia IRIS:
03 - Contributo in volume
Keywords:
Alluvial aquifers, Glacio-fluvial environments, Heterogeneity, Hydrostratigraphy, Modelling, Pleistocene
Elenco autori:
R. Bersezio, L. Pessina, L. Cattaneo, E. Cavalli, F. Felletti, M. Giudici, M. Mele
Link alla scheda completa:
Titolo del libro:
10th International Conference on Fluvial Sedimentology. Conference programme and Abstracts Volume