Faults and fractures in central West Greenland: onshore expression of continental break-up and sea-floor spreading in the Labrador – Baffin Bay Sea

Abstract

The complex Ungava fault zone lies in the Davis Strait and separates failed spreading centres in the Labrador Sea and Baffin Bay. This study focuses on coastal exposures east of the fault-bound Sisimiut basin, where the onshore expressions of these fault systems and the influence of pre-existing basement are examined. Regional lineament studies identify five main systems: N–S, NNE–SSW, ENE–WSW, ESE–WNW and NNW–SSE. Field studies reveal that strike-slip movements predominate, and are consistent with a ~NNE–SSW-oriented sinistral wrench system. Extensional faults trending N–S and ENE–WSW (basement-parallel), and compressional faults trending E–W, were also identified. The relative ages of these fault systems have been interpreted using cross-cutting relationships and by correlation with previously identified structures. A two-phase model for fault development fits the development of both the onshore fault systems observed in this study and regional tectonic structures offshore. The conclusions from this study show that the fault patterns and sense of movement on faults onshore reflect the stress fields that govern the opening of the Labrador Sea – Davis Strait – Baffin Bay seaway, and that the wrench couple on the Ungava transform system played a dominant role in the development of the onshore fault patterns.

The role of pre‐existing structures during rifting, continental breakup and transform system development, offshore West Greenland

“…). Here, the cause of this changing distribution is considered, alongside the relationship of the offshore structures and those previously published from onshore (Japsen et al ., ; Wilson et al ., ).…”

“…In particular, on Line G it appears that the ITZ may correspond to the bounding fault of the basin shown on this line as the approximate continuation of the ITZ would be expected here, the dip direction of the basin bounding fault is similar and the reflection characteristics of the basement either side of this structure are what would be expected based on the onshore geology, i.e. the folded fabrics of the CNO and SNO display different internal reflectivity compared to within the ITZ (Wilson et al ., ).…”

“…() and Wilson et al . (). NSSZ, Nordre Strømfjord shear zone; NISZ, Nordre Isortoq shear zone; ITZ, Ikertôq thrust zone; NNO, Northern Nagssugtoqidian orogeny; CNO, Central Nagssugtoqidian orogeny; SNO, Southern Nagssugtoqidian orogeny; SNF, Southern Nagssugtoqidian front; NAC, North Atlantic Craton.…”

“…Reworked Achaean gneisses form a large majority of the NO (Van Gool et al ., ). The NO contains multiple onshore structures that represent candidates for reactivation and reworking during rifting (Wilson et al ., ).…”

Segmentation of Rifts Through Structural Inheritance: Creation of the Davis Strait

“…The Palaeoproterozoic Nagssugtoqidian orogenic belt to the north of the North Atlantic Craton was first identified as a persistent (>2.5 Gyr) tectonic lineament by Watterson (1975), who regarded the boundary as a lithosphere-scale structure due to the presence of Cambrian age kimberlites that are crosscut by Mesozoic age pseudotachylytes (Grocott, 1977). Subsequent investigation of brittle deformation in exposures of the Nagssugtoqidian Orogen adjacent to the Davis Strait by Wilson et al (2006) revealed a two-phase model for fault development that is compatible with the development of the Mesozoic to Cenozoic continental margin offshore (Chalmers et al, 1993;Oakey & Chalmers, 2012). Wilson et al (2006) found that the Phase 1 generally N-S trending normal faults were kinematically compatible with the early NW-SE opening of the Labrador Sea-Davis Strait-Baffin Bay seaway in the Cretaceous to Paleocene.…”