Rift‐Parallel Strike‐Slip Faulting Near the Iceland Plate Boundary Zone: Implications for Propagating Rifts. Issue 12 (17th December 2018)

• Record Type: Journal Article
• Authors: Karson, J. A.; Farrell, J. A.; Chutas, L. A.; Nanfito, A. F.; Proett, J. A.; Runnals, K. T.; Sæmundsson, K.
• Is Part Of: Tectonics. Volume 37:Issue 12(2018)
• Page Start: 4567
• Page End: 4594
• Publication Date: 2018-12-17
• Subjects: strike‐slip faults -- rift propagation -- seafloor spreading -- fault kinematics -- Iceland; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2018TC005206
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: Strongly lineated terrain outside of Iceland's active plate boundary zones is created by faults and dikes aligned with the rift zones where they formed, similar to the spreading fabric defined by abyssal hills generated at mid‐ocean ridge spreading centers. As expected, rift‐parallel normal faults and fissures dominate in the active rift zones, but in older crust to the east and west, faults with strike‐slip and oblique‐slip displacements dominate. Some areas have widespread, small‐scale, strike‐slip, and oblique‐slip faults, while others have more widely spaced, larger, strike‐slip fault zones. In most cases, the strike‐slip and oblique‐slip faults strike subparallel to nearby older dikes and normal faults assumed to indicate the orientation of the rift zones where they formed. Strike‐slip displacements overprinting normal faults and along dike margins suggest reactivation of spreading‐related zones of weakness. More complicated fault geometries and kinematics occur near the oblique rifts and the major transform fault zones. The sense of movement on the strike‐slip and oblique‐slip faults is broadly systematic with respect to the active Northern and Eastern Rift Zones supporting the interpretation that they are the result of crustal block rotations on either side of rift zones that propagate to the north and south away from the center of the Iceland hot spot. Similar fault kinematics may occur along mid‐ocean ridges and other magmatic rifts where rift propagation occurs on a range of scales. Plain Language Summary: This study documents widespread strike‐slip faulting subparallel to the adjacent active rift zones of Iceland. This type of faulting is enigmatic because rift zones in Iceland and along mid‐ocean ridge spreading centers are expected to be normal faults associated with tectonic extension. We interpret the strike‐slip faults as the result of internal deformation of crustal blocks that rotate due to rift propagation. Similar faulting may occur near propagating rifts along mid‐ocean ridges on the deep sea floor. Key Points: Numerous faults sub‐parallel to Iceland's active rift zones have strike‐slip displacements and contribute to the strongly lineated terrain Kinematics of faulting are interpreted as the result of crustal deformation caused by rift propagation away from the Iceland hot spot Similar patterns of abyssal hills near mid‐ocean ridges suggest that strike‐slip faulting may be common near propagating ridge segments