A database of pumping tests in crystalline rocks: Lithostratigraphic controls on transmissivity and its log-normal distribution (Armorican Massif, France)

Armorican Massif, Brittany, France This study compiled a comprehensive database from 485 pumping tests performed in crystalline aquifers within a single region (Brittany, France; 27,209 km²). The database, publicly accessible through an online repository, currently includes 485 transmissivity/hydraulic conductivity values and 195 storage coefficients. This framework will be progressively expanded to cover the entire Armorican Massif. The dataset enables a detailed analysis of the relationships between hydrodynamic parameters and geological settings, providing a refined understanding of how lithological and structural factors (such as scale, age, rock type, mineralogy and tectonic history) influence aquifer transmissivity. Statistical analyses reveal significant differences in transmissivity among certain crystalline lithologies when examined at an appropriate geological resolution, although substantial overlap of transmissivity values persists across most groups. These results also confirm the log-normal nature of transmissivity distribution, a feature often assumed but rarely supported by such extensive dataset. Overall, this work provides a quantitative and comparative assessment across 27 distinct crystalline rock settings, offering new insights into the lithological controls of transmissivity variability. In particular, the database constitutes a valuable resource for numerical modeling, geothermal potential mapping, and comparative hydrogeological studies across different crystalline terrains. • Comprehensive database including 485 transmissivity values and 195 storage coefficients from crystalline rock aquifers. • Analysis of the relationships between hydrodynamic parameters and detailed geological settings. • Evidence supporting the log-normal distribution of transmissivity values. • Statistical demonstration of significant transmissivity differences between some crystalline lithologies. • Quantitative assessment and comparative analysis across 27 distinct crystalline rock settings.