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

Robert W Wilson,Knud Erik S Klint,Robert E Holdsworth,James A Chalmers,Kenneth J.W Mccaffrey,Jeroen A.M Van Gool

doi:10.34194/geusb.v11.4931

Robert W Wilson, Knud Erik S Klint + Show 4 more

Open Access

https://doi.org/10.34194/geusb.v11.4931

Copy DOI

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.

Highlights

Pre-existing heterogeneities in the continental crust, such as shear zones and terrain boundaries, have long been known to influence the structure and development of later deformation events (Butler et al 1997; Holdsworth et al 1997, and references therein)
The development of Mesozoic to Cenozoic basins offshore West Greenland appears to be strongly controlled by faults
A simple two-stage model has been outlined to explain the complex fault patterns exhibited in onshore exposures of the central Nagssugtoqidian orogen (Fig. 10)

Summary

Introduction

Pre-existing heterogeneities in the continental crust, such as shear zones and terrain boundaries, have long been known to influence the structure and development of later deformation events (Butler et al 1997; Holdsworth et al 1997, and references therein). The sedimentary basins of the Labrador Sea – Baffin Bay region are situated west of Greenland (Fig. 1) and are early Cenozoic failed spreading centres (Chalmers & Pulvertaft 2001), separated by the Davis Strait. The orientation of the Davis Strait relative to the proposed spreading centres in the Labrador Sea and Baffin Bay is consistent with the geometry of an ‘extensional transform zone’ (Taylor et al 1994). Steep basement fabrics of the Nagssugtoqidian orogen trend highly obliquely to these offshore structures (Fig. 1) and coincide with this ‘step-over zone’ in the Davis Strait. Fault systems fundamental to the development of sedimentary basins in the Davis Strait are exposed onshore in West Greenland. The onshore fault systems of central West Greenland were studied in order to improve

Methods

Discussion

Conclusion