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Strain Partitioning and Variation in Style of Deformation During Continental Extension, Eastern Baffin Bay, West Greenland


Understanding the evolution from continental rift basins to a passive continental margin is essential for understanding broader lithospheric stretching processes, yet is often limited by the scale of observation, the development of a failed rift rather than a fully passive margin, and data availability. Baffin Bay, offshore Greenland, represents an area where the evolution of large-scale (~200 km long, ~50-70 Myr duration) rift basins to a passive margin can be investigated, thus bridging the gap between small-scale (<20 km-long, <10 Myr) fault evolution models and lithospheric-scale geodynamic models. We apply sequence stratigraphic principles on 2D seismic reflection profiles to understand the tectono-stratigraphic evolution of the study area. In particular, by applying a mega-sequence approach to interpret the profiles we can assess the distribution of lithospheric and crustal effects on subsidence and accommodation space. Furthermore, mapping of the TWT thicknesses of individual syn-rift packages enables us to constrain the evolution of its depocentres. Rifting initiation in the Melville Bay Graben, in the east of the study area, was dominated by 5-20 km long, ENE and WSW-dipping, Early Cretaceous fault segments. Further strain was accommodated via fault linkage, with activity localising on the eastern side, eventually forming the ~200 km long basin-bounding Melville Bay Fault in the Late Cretaceous-Early Paleocene. In the Kivioq and Upernavik Basins, to the west, rifting resulted in smaller (~5-20 km wide) half grabens that are broadly symmetrical over a ~70 km scale. Cumulative syn-rift sediment accumulation is highly variable across the margin with > 5500 ms (TWTT) preserved in the Melville Bay Graben as compared to ~1500 ms in the other basins. In contrast, Eocene post-rift sedimentation is much thinner in the Melville Bay Graben (2000 ms) compared to the western basins (~4000 ms). This stratigraphic thickness asymmetry in Eastern Baffin Bay is also manifested in the interpreted structural styles. These observations lead us to propose a hybrid, scale-dependent model to explain this strain partitioning and variation in deformation style. Eastern Baffin Bay, therefore, provides insights not only to the larger scale processes involved in the coalescing of rift basins into a margin-scale basin but also how strain is partitioned during the break-up phase of lithospheric separation.