Crustal extension and salt tectonics of the Danmarkshavn Ridge and adjacent basins, NE Greenland

Abstract

Abstract Modern 2-D seismic data are used to evaluate the rift architecture, salt tectonics, and structural evolution of the Danmarkshavn Ridge and adjacent basins on the NE Greenland shelf. The Danmarkshavn Ridge is a segmented horst between landward- and basinward-dipping crustal faults. Extension was ongoing from the Devonian through the Cretaceous, with Paleozoic and Mesozoic faults trending mostly N–S and NNE-SSW, respectively. One Paleozoic fault is a low-angle, basinward-dipping detachment interpreted as a reactivated Caledonian thrust/shear zone, with the Moho in its footwall as shallow as 16 km. Salt on the NE Greenland shelf is postulated to be Pennsylvanian to Early Permian in age by analogy to the Gipsdalen Group evaporites of the conjugate Barents Sea margin. There are at least two, and possibly four, distinct mobile levels. The salt layers partly decouple the deformation, with drape folds and truncated drape folds above basement faults. Listric normal faults detached on the upper salt are mostly tectonic but also partly gravity-driven, balanced by salt-cored contractional anticlines. Passive diapirs are present only at the upper salt level. Some were triggered by extension, initiating as reactive diapirs, and others broke out of the contractional folds. Quantitative restorations of eight serial cross sections illustrate the three-dimensional evolution. The results are dependent on the accuracy of the horizon age assignments, which are constrained only for shallow levels in the Danmarkshavn Basin. Given this caveat, the restorations suggest that Permo-Triassic extension was relatively slow but gradually increased from south to north. The main phase of rifting, during the Jurassic and especially Early Cretaceous, was greatest in the southern and central portions of the study area. Upper Cretaceous extension was relatively minor, presumably due to late-stage hyperextension shifting basinward into the Thetis Basin prior to the onset of seafloor spreading at the beginning of the Eocene.