Flexural plate representation of Danish Central Graben evolution

Abstract

An inverse flexural plate method is used on five dip seismic lines across the northeastern Danish Central Graben to recover original unloaded plate parameters. The original plate showed remarkable consistency of parameters determined independently from each of the seismic lines with average rigidity D = 10 20.6±0.2 Nm; bending moment M = 14.4±0.8 N, and dip angle θ = −7.5±1.5°. By sequentially adding the sedimentary units to the average “bare” basement, it is shown that the 3-D geometry of the basin had major downward warp, and high sedimentary fill, to the SE at Triassic time, leaving the northern section open to possible erosion during Early and Middle Jurassic time. The deep southern basin was then filled by sediments during late Jurassic time, and a new depocenter created across the central and SW parts of the basin. This newer depocenter was then filled during Cretaceous time. The combined 3-D flexure of the basement plate and corresponding sediment fill behaviors with time are indicative of corresponding lithologic variations across the basin and with suspected organic rich sediments. The integrated evolution of basement, sediments and depocenter behavior points to the utility of the inverse procedure for improving our understanding of basinal evolution. The relatively low values of rigidity compared to estimated oceanic crust values point to a thin crust below the sediments and to a higher heat flux through the basement relative to that through oceanic crustal material.