Airborne and ground geophysical investigation of the abandoned salt mine environment along the Stassfurt-Egeln Anticline, Germany

Abstract

In the area of the 1200-year-old town of Stassfurt, where the world’s first potash mine was opened in 1852, sinkholes emerged during mining and the town’s centre slowly subsided. Mining has increased the subsidence due to collapses and uncontrolled flooding of abandoned salt mineworkings, the dissolution of salt in the mines, and the pump-driven drainage system. In order to investigate possible consequences of salt-mine flooding, this area was selected for the study of the dynamic processes in flooded or abandoned mineworkings and their overburden. As part of a multi-disciplinary research project, the German Federal Institute for Geosciences and Natural Resources (BGR) conducted an airborne geophysical survey covering the salt anticline in summer 2007 with the aim of acquiring extensive electrical conductivity datasets to show the regional hydrogeological and geological structures down to about 100 m depth. Areas with distinct conductivity anomalies were subsequently selected for more detailed studies using ground geophysical methods such as DC geoelectrics and transient electromagnetics (TEM). The conductivity data revealed several hydrogeologically important features, such as the distribution of salt water, areas of salt-water rise, Quaternary channels, and fresh-water influxes. The airborne data also served as base-line data for ground follow-up studies and 3D hydrogeological and geological modelling.