Massive New Atlas Maps the Rock Properties Beneath Germany’s Crystalline Basement

Beneath Germany’s rolling hills, river valleys, and dense urban corridors lies a vast realm of ancient crystalline rock, some of it billions of years in the making, that has long attracted the attention of geologists hunting for geothermal energy and evaluating sites for the safe disposal of high-level radioactive waste. Yet despite this growing interest, the fundamental physical character of these deep rocks has remained scattered across decades of studies, unpublished survey reports, and institutional archives. A team led by Leandra Maren Weydt of the Department of Geothermal Science and Technology at Technische Universität Darmstadt, together with colleagues from the Helmholtz Centre for Geosciences (GFZ) in Potsdam, has now changed that. In a preprint under review for the journal Earth System Science Data, the researchers present the first release of the AMPEDEK database, a standardized, open-access national reference compilation of geochemical, petrophysical, and mechanical rock properties for Germany’s crystalline basement.

The scale of the new resource is striking. The repository currently holds approximately 25,700 data points covering up to 34 distinct parameters, measured on more than 8,200 samples drawn from over 3,400 sampling locations across eight German federal states. These numbers represent the first time that such a broad and statistically robust body of rock property information has been brought together in a single, unified framework for the country. Until now, systematic datasets covering the major crystalline and metamorphic basement units and their physiomechanical characteristics were scarce, fragmented, or lacked the metadata needed for rigorous evaluation. The AMPEDEK project was designed specifically to close this gap, and its first release marks a milestone for subsurface research in Germany.

Building the database required an unusual combination of archival detective work and fresh laboratory science. The team compiled, evaluated, and integrated existing data from more than 40 published studies, alongside material contributed by geological surveys. To fill the remaining holes in coverage, the researchers conducted their own sampling and measurement campaigns, retrieving approximately 650 cylindrical plugs from drill cores and outcrop samples and analyzing them systematically for their mineralogical, geochemical, petrophysical, and rock mechanical properties. Particular emphasis was placed on sampling a broad spectrum of lithologies, ensuring that the major crystalline units of the German basement are represented rather than only the rock types that happen to be well studied or commercially fashionable.

What makes the database more than a simple pile of numbers is its structure. Every entry is linked through unique sample identifiers that connect metadata, geochemistry, petrography, and physiomechanical rock properties. This means a user can trace a single measurement back to its parent sample, its location, its rock type, and the conditions under which it was measured. In an era when machine learning models and numerical simulations are only as good as the data fed into them, that kind of traceability is essential. It allows researchers to assess data quality, compare results across studies, and avoid the silent errors that arise when heterogeneous datasets are merged without consistent documentation.

The practical motivation behind the project is rooted in some of the most consequential engineering challenges Germany faces. Deep geothermal energy, which taps heat from hot crystalline rocks far below the surface, depends on knowing how those rocks conduct heat, how easily fluids move through their fracture networks, and how they deform under stress. The safe storage of high-radioactive nuclear waste, meanwhile, demands an intimate understanding of the mechanical strength, mineralogy, and long-term stability of the host formations. For both applications, a comprehensive and statistically robust understanding of rock characteristics is essential for reservoir characterization of the deep subsurface, accurate planning of exploration campaigns, parameterization of predictive three-dimensional geological models, interpretation of geophysical data, and execution of numerical thermo-hydraulic-mechanical-chemical simulations. Better data translate directly into reduced economic risks and lower project uncertainties.

The parameters captured in the database span the full range of properties that matter for such work. Petrophysical measurements characterize how rocks respond to heat, electricity, magnetism, and fluid flow, providing the bridge between laboratory samples and the geophysical signals recorded in the field. Mechanical tests quantify strength, stiffness, and deformation behavior, which govern whether a fractured reservoir will hold open pathways for circulating water or seal itself shut under pressure. Geochemical and mineralogical data reveal the composition and history of each rock unit, offering clues about alteration, fracturing, and the processes that shaped the basement over hundreds of millions of years. With up to 34 parameters available per sample, the compilation allows researchers to examine how these properties co-vary, a critical step for building predictive models that can estimate conditions at sites where no direct measurements exist.

The open-access nature of the release amplifies its value. Hosted through the TU Darmstadt data repository, the database is freely available to researchers, industry, and public authorities, in line with the principles of findable, accessible, interoperable, and reusable research data. For early-stage exploration, this means companies and geological surveys can perform preliminary reservoir assessments without commissioning expensive new drilling programs. For the scientific community, the compilation provides a robust empirical foundation for validating analytical measurement methods, since laboratories can benchmark their results against a large, standardized reference population. And for modelers, it supplies the ground truth needed to test whether simulated rock behavior matches reality at the scale of real geological formations.

The authors are explicit that this first release is a beginning rather than an end. Future efforts will focus on expanding the database toward regions with low data density, ensuring that the coverage of Germany’s crystalline basement becomes more geographically even. They also plan high-temperature and high-pressure experiments designed to improve understanding of how rock parameters vary under in situ conditions. This latter point is scientifically crucial: laboratory measurements made at room temperature and ambient pressure may not faithfully represent the behavior of rocks kilometers underground, where they are subjected to intense heat and confining stress. By characterizing these variations experimentally, the team aims to make the database even more directly applicable to real subsurface conditions.

For Germany’s energy transition, the timing of the release could hardly be more significant. The country is actively pursuing deep geothermal energy as a low-carbon heat and power source, and it continues to search for a permanent repository for its nuclear waste, a process in which the crystalline basement is among the candidate host rock environments under consideration. Both endeavors require exactly the kind of systematic, quality-controlled property data that AMPEDEK now provides. A drilling campaign that costs tens of millions of euros can succeed or fail on the accuracy of the assumptions made before the drill bit ever turns, and every improvement in the underlying data reduces the gamble.

The AMPEDEK database also sets a template that other countries could follow. Crystalline basement rocks underlie much of central and northern Europe, and comparable data fragmentation problems exist almost everywhere. By demonstrating how literature compilation, geological survey cooperation, and targeted new measurements can be woven into a single, sample-linked, open-access framework, the German team has shown a practical path from scattered data to national reference resource. As the database grows through future releases, it is likely to become an indispensable tool not only for German geoscientists but for the international community studying the deep critical zone where energy, waste, and water challenges converge beneath our feet.

Subject of Research: A standardized open-access database of geochemical, petrophysical, and mechanical rock properties of Germany's crystalline basement

Article Title: Atlas of geochemical, petrophysical and mechanical rock properties of the crystalline basement in Germany – first release

Article References: Weydt, L. M., Ramírez-Guzmán, Á. A., Muhl, L., Deon, F., Schleicher, A. M., & Sass, I. (2026). Atlas of geochemical, petrophysical and mechanical rock properties of the crystalline basement in Germany – first release. https://doi.org/10.5194/essd-2026-555

Image Credits: AI Generated

DOI: 10.5194/essd-2026-555

Keywords: crystalline basement, rock properties, petrophysics, geochemistry, geothermal energy, nuclear waste storage, AMPEDEK database, Germany, reservoir characterization, open-access data, rock mechanics, subsurface exploration