Basin-scale development of giant collapse structures induced by gypsum diagenesis

Abstract

Across buried sedimentary basins, the dissolution-prone nature of evaporite sequences drives the formation of collapse structures (e.g., sinkholes), fundamentally transforming landscapes at large scales. Understanding where, why, and how such structures form is crucial, given that they pose geological hazards that may threaten human safety and infrastructure stability or may affect subsurface resource extraction and geological storage. We use three-dimensional seismic reflection and borehole data from the Southern North Sea Basin to document giant (kilometers wide and several hundred meters deep) collapse structures within the Zechstein Supergroup (Permian) that developed at the basin scale (>10,000 km2). Critically, these structures invariably overlie gypsum buildups capped by thick halite, with seismic-stratigraphic relationships enabling precise dating and facilitating accurate modeling. We propose that the transformation of gypsum to anhydrite during early burial initiated the extrusion of NaCl-undersaturated water, which provoked dissolution of the capping halite, leading to collapse at the depositional surface. The resulting landscape was buried and thus preserved by a potash infilling unit. To the best of our knowledge, neither the scale nor the genetic mechanism of these structures has previously been documented in the stratigraphic record.