Extension parallel to the rift zone during segmented fault growth: application to the evolution of the NE Atlantic

• Published in: Solid Earth
• Main Authors: Bubeck, Alodie, Walker, Richard J., Imber, Jonathan, Holdsworth, Robert E., MacLeod, Christopher J., Holwell, David A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union (EGU), Copernicus Publications 2018
• Subjects: Science & Technology; Physical Sciences; Geochemistry & Geophysics; RELAY RAMPS; KILAUEA-VOLCANO; CONTINENTAL BREAKUP; SPREADING CENTERS; TRANSFORM FAULTS; STRUCTURAL STYLE; STRESS-FIELDS; NATIONAL-PARK; FLUID-FLOW; PROPAGATION; Faroe Islands; Greenland; Krafla; Perez; Diaz; Leicester; East Greenland; Faroes; Iceland
• Online Access: https://www.solid-earth.net/8/1161/2017/; http://hdl.handle.net/2381/40744; https://doi.org/10.5194/se-8-1161-2017

Raw data for study sites on the Faroe Islands are published in Walker (2010) and Walker et al. (2011). Field locations may be found in Figs. 3, 5, 8, and 9. Raw data are not currently available due to ongoing data analysis but will be made available to the broader community in due course. For specific requests in the meantime, please contact A. Bubeck ([e-mail]). The mechanical interaction of propagating normal faults is known to influence the linkage geometry of first-order faults, and the development of second-order faults and fractures, which transfer displacement within relay zones. Here we use natural examples of growth faults from two active volcanic rift zones (Koa`e, island of Hawai`i, and Krafla, northern Iceland) to illustrate the importance of horizontal-plane extension (heave) gradients, and associated vertical axis rotations, in evolving continental rift systems. Second-order extension and extensional-shear faults within the relay zones variably resolve components of regional extension, and components of extension and/or shortening parallel to the rift zone, to accommodate the inherently three-dimensional (3-D) strains associated with relay zone development and rotation. Such a configuration involves volume increase, which is accommodated at the surface by open fractures; in the subsurface this may be accommodated by veins or dikes oriented obliquely and normal to the rift axis. To consider the scalability of the effects of relay zone rotations, we compare the geometry and kinematics of fault and fracture sets in the Koa`e and Krafla rift zones with data from exhumed contemporaneous fault and dike systems developed within a > 5×104 km2 relay system that developed during formation of the NE Atlantic margins. Based on the findings presented here we propose a new conceptual model for the evolution of segmented continental rift basins on the NE Atlantic margins. This study was funded via Richard J. Walker’s University of Leicester start-up fund, as part of Alodie Bubeck’s PhD project. Observations crucial to this study were made during Richard J. Walker’s PhD research, which was funded by Statoil (UK) Ltd. Thanks to Pierpaolo Guarnieri for making it possible to collect data in east Greenland, and thank you to the Føroya Dàtusavn for access to Faroes aerial imagery. We thank Richard England for discussions during manuscript preparation. We thank reviewers Atle Rotevatn and Lucia Perez-Diaz for constructive feedback, which greatly improved the clarity of this manuscript. We gratefully acknowledge Don Swanson (HVO) and Mike Poland (formerly HVO) for their help and advice during fieldwork planning and data collection, and we thank the National Park Service for granting a research permit to conduct fieldwork in the Koa‘e fault system. Aerial lidar datasets were provided by the OpenTopography Facility with support from the National Science Foundation under NSF award nos. 1226353 & 1225810 (not related to this study). Peer-reviewed Publisher Version