Gravity-driven salt tectonics in extensional basins

PROJECT DESCRIPTION

In salt-bearing rift basins, flow of the viscous salt can be driven by tectonic extension, sedimentary loading and tilting of the base of the salt layer. The latter process can cause basinward salt flow and gravity gliding of overburden sedimentary layers. The main objective of this project is to investigate under which geological conditions (e.g. minimum basin slope, thickness of the overburden, etc.) gravity gliding is induced or prevented and which characteristic salt and supra-salt structures are indicators for gravity-driven processes in salt-bearing rift basins. The newly designed analog apparatus allows us to simulate the development of a rift basin combined with progressive tilting of the basin flanks to identify structures and driving mechanisms characteristic for either gravity gliding or tectonic extension (Warsitzka et al., 2021). Viscous silicone putty and mixtures of granular sand and cenospheres are used as analogs for salt and overburden sediments, respectively. The deformation and displacement patterns of the experimental surface are recorded and analysed by a 3D digital image correlation technique by LaVision. Along with this analog modeling study, seismic data and geological cross sections of relevant salt-bearing rift basins (e.g. Polish Basins, North Sea Basins) are analysed and restored so that they can serve as direct comparison of the modeling results.

The modelling study is performed in cooperation with the Institute of Geological Science of the Polish Academy of Science and the Federal Institute for Geosciences and Natural Resources (Hanover, Germany).

Setup of the extensional box, which is roughly 2 m long and 80 cm wide. The apparatus can simulate crustal-scale extension and thermal subsidence. The stereoscopic cameras are part of the StrainMaster system by LaVision GmbH and used to analyse 3D displacement.

Results of an experiment in the extensional apparatus. The layering of the materials consists of viscous silicone (brown) to simulate a salt layer and loose granular mixture (grey) to simulate brittle sediments. The basal plates mimic the extension of a graben structure and the tilting of the graben flanks (resulting from thermal subsidence in nature). The results show that deformation patterns close to the graben structures are overprinted by gravity gliding due to the tilting of the flanking plates.