Fig. 6: Chalk deformation structures below the crater floor and brim, showing extensive surface pits and volume loss following impact.
From: Multiple lines of evidence for a hypervelocity impact origin for the Silverpit Crater
a True vertical depth subsea (TVDSS) structure maps blended with the Variance attribute for the Top Chalk Group, generated from both the Greater NEP 3D and PGS SNS 3D MegaMerge seismic volumes. The central uplift and moat display pervasive surface pits of 50-500 m diameter. These may indicate significant devolatilization of the chalk following impact, with vaporised water and CO2 from carbonate catastrophically released below the crater centre during the crater modification stage. b Chalk thickness map, showing substantial thinning of the chalk below the crater floor. Contour increment is 50 m. An estimated rock volume of 0.9–2.2 km3 is missing from the chalk below the crater floor. c Seismic section flattened at a shallow horizon (black dashed line) within the Paleogene clay, to remove the effect of post-impact folding and reconstruct crater geometry. The pitted Top Chalk sits below a vertical zone of disruption (VZD) that we interpret as evidence of fluid escape (devolatilization) during the crater modification stage.
