Fault block basins exposed along NE Greenland provide insights into the tectonic evolution of East Greenland and the Norwegian-Greenland Sea. We present a new geological map and cross sections of the Traill Ø region, NE Greenland, which formed the western margin of the Vøring Basin prior to Cenozoic seafloor spreading. Observations support a polyphase rift evolution with three rift phases during Devonian-Triassic, Jurassic-Cretaceous, and Cenozoic time. The greatest amounts of faulting and block rotation occurred during Cenozoic rifting, which we correlate with development of the continent- ocean transition after ca. 56 Ma and the Jan Mayen microcontinent after ca. 36 Ma. A newly devised macrofaunal-based stratigraphic framework for the Cretaceous sandy mudstone succession provides insights into Jurassic- Cretaceous rifting. We identify a reduction in sedimentation rates during the Late Cretaceous; this corresponds to a transition from structurally confined to unconfined sedimentation that coincides with increased clastic sedimentation to the Vøring and Møre Basins derived from East Greenland. With each rift phase we record an increase in the number of active faults and a decrease in the spacing between them. We attribute this to fault block rotation that leads to an excess build-up of stress that can only be released by the creation of new steep faults. In addition, we observe a stepwise migration of deformation toward the rift axis that we attribute to preexisting lithospheric heterogeneity that was modified during subsequent rift and post-rift phases. Such observations are not readily conformable to classic rift evolution models and highlight the importance of post-rift lithospheric processes that occur during polyphase rift evolution.
We thank the science editor, Shanaka de Silva, the associate editor, and Rebecca Bell and Christian Haug Eide for helpful and constructive reviews that improved this manuscript, and Simon Price for helpful discussion during revision of the manuscript. Field work was conducted by us and by S.P. Price, A.H. King, and T.C. Kinnaird. We thank Simon Schneider (CASP), Sarah Finney, and the Conservation Laboratory (Brighton Building, Department of Earth Science, University of Cambridge) for assistance and use of facilities for photography of fossil samples used in Figures 8 and 9. We thank the Geological Survey of Denmark and Greenland (GEUS) for providing and granting permission of use of water body and coastline information for the mapped region. We gratefully acknowledge Crispin Day, Clive Johnson, Kenn Nielsen, Søren Rysgaard, and Asty Taylor; without their logistical help none of this work could have happened.