Geophysical analysis of an area affected by subsurface dissolution - case study of an inland salt marsh in northern Thuringia, Germany

authored by

Sonja H. Wadas, Hermann Buness, Raphael Rochlitz, Peter Skiba, Thomas Günther, Michael Grinat, David C. Tanner, Ulrich Polom, Gerald Gabriel, Charlotte M. Krawczyk

Abstract

The subsurface dissolution of soluble rocks can affect areas over a long period of time and pose a severe hazard. We show the benefits of a combined approach using P-wave and SH-wave reflection seismics, electrical resistivity tomography, transient electromagnetics, and gravimetry for a better understanding of the dissolution process. The study area, "Esperstedter Ried"in northern Thuringia, Germany, located south of the Kyffhäuser hills, is a large inland salt marsh that developed due to dissolution of soluble rocks at approximately 300 m depth. We were able to locate buried dissolution structures and zones, faults and fractures, and potential fluid pathways, aquifers, and aquitards based on seismic and electromagnetic surveys. Further improvement of the model was accomplished by analyzing gravimetry data that indicates dissolution-induced mass movement, as shown by local minima of the Bouguer anomaly for the Esperstedter Ried. Forward modeling of the gravimetry data, in combination with the seismic results, delivered a cross section through the inland salt marsh from north to south. We conclude that tectonic movements during the Tertiary, which led to the uplift of the Kyffhäuser hills and the formation of faults parallel and perpendicular to the low mountain range, were the initial trigger for subsurface dissolution. The faults and the fractured Triassic and lower Tertiary deposits serve as fluid pathways for groundwater to leach the deep Permian Zechstein deposits, since dissolution and erosional processes are more intense near faults. The artesian-confined saltwater rises towards the surface along the faults and fracture networks, and it formed the inland salt marsh over time. In the past, dissolution of the Zechstein formations formed several, now buried, sagging and collapse structures, and, since the entire region is affected by recent sinkhole development, dissolution is still ongoing. From the results of this study, we suggest that the combined geophysical investigation of areas prone to subsurface dissolution can improve the knowledge of control factors, hazardous areas, and thus local dissolution processes.

Organisation(s)

Institute of Geology

External Organisation(s)

Leibniz Institute for Applied Geophysics (LIAG)
Federal Institute for Geosciences and Natural Resources (BGR)
Helmholtz Centre Potsdam - German Research Centre for Geosciences (GFZ)
Technische Universität Berlin

Type

Article

Journal

Solid Earth

Volume

13

Pages

1673-1696

No. of pages

24

ISSN

1869-9510

Publication date

02.11.2022

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Soil Science, Geophysics, Geology, Geochemistry and Petrology, Earth-Surface Processes, Stratigraphy, Palaeontology

Sustainable Development Goals

SDG 15 - Life on Land

Electronic version(s)

https://doi.org/10.5194/egusphere-2022-164 (Access: Open)
https://doi.org/10.5194/se-13-1673-2022 (Access: Open)