Hydrogeological Significance of Contrasting Fault Types and Deformation Styles in Unconsolidated Sediments, Corinth Rift Basin, Greece

The half-graben system of the Gulf of Corinth, Greece, features intra-basinal faults on the south-eastern rift flank margin that defines the northern coastline of the Peloponnesus mountains. Small-scale faults with throws up to tens of meters cut through poorly consolidated deltaic sediments characterized by graded clastic sediments which were uplifted during over the last ~2 Ma. On the regional scale, these alluvial sediment bodies are bound by crustal scale faults that have throws ≥~100 m. First outcrop studies along the minor faults indicate that a large variety of deformation styles exists. In these very heterogeneous sediments where fine-grained sediments (marls and clays) are interbedded with gravel units, the style of along-fault deformation ranges from clay-smearing to gravel-drag. We hypothesize that these small scale faults can effectively compartmentalize individual aquifers reducing the potential for continuous fluid flow paths within them. The basement faults, on the other hand, have large enough throws to off-set entire sedimentary wedges juxtaposing loose sediments against basement rock. However, along the scarps formed by these major faults sediments from the wedge can be dragged and provide a hydraulic path-way between units in the footwall and hangingwall that would otherwise be separate aquifer bodies.