Distributed Deformation in an Oceanic Transform System: Applying Statistical Tools to Structural and Paleomagnetic Data Near the Húsavík-Flatey Fault, Northern Iceland

Sarah J. Titus, William Chapman, Andrew J. Horst, Maxwell Brown, Joshua R. Davis

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The right-lateral Húsavík-Flatey fault is part of the Tjörnes Fracture Zone, which links the offshore and onshore rift axes in northern Iceland. There has been debate about whether rocks near this fault have accommodated distributed off-fault deformation, which is testable using paleomagnetic data. Recent studies from Flateyjarskagi show clockwise declination deflections that are largest near the fault. We augment these data with new structural and paleomagnetic measurements from 106 lava flows across three peninsulas—Flateyjarskagi, Tröllaskagi, and Tjörnes—also finding clockwise deflections that vary with distance from the fault. To test whether the deflections could be caused by off-fault deformation, we combine our measurements with other regional data sets, applying several statistical tools including regressions of structural or paleomagnetic directions versus fault-normal distance. To evaluate the significance and uncertainties of the regressions, we use permutation tests and bootstrapping. For Flateyjarskagi, our analysis suggests that lavas and dikes were deformed together; the regression results predict 4°–6° of rotation per kilometer about a steep, but not vertical, axis. Rocks on Tröllaskagi hint at similar spatial patterns with fault distance, but the data quality precludes a full analysis. Rocks on Tjörnes show no spatial patterns, but they preserve a temporal history, where rotation seems to have ceased after deposition of the Pliocene-age Tjörnes beds. Using constraints from our statistical analyses, geochronology, and comparisons with the transform system in southern Iceland, we propose several modifications to models for the evolution of axial rift zones in northern Iceland.

Original languageEnglish (US)
Pages (from-to)3986-4017
Number of pages32
JournalTectonics
Volume37
Issue number10
DOIs
StatePublished - Oct 2018
Externally publishedYes

Bibliographical note

Funding Information:
The paleomagnetic data are listed in the Supporting Information. For their assistance in the field and good humor under all sorts of weather conditions, we thank Willa Rowan and Ella Fadely. We gratefully acknowledge Thor from the Guesthouse Sigtun in Húsavík who assisted with on-site logistics. Our paleomagnetic processing at the IRM would not be possible without the amazingly kind staff, especially Dario Bilardello and Mike Jackson. We thank Kristján Sæmundsson and Andy Poppick for helpful conversations about the geology of Iceland and statistics, respectively, although any mistakes in our approach and interpretations are our own. We also thank Seth Waag-Swift for drafting the regional geologic map and uncovering a late-stage error in our statistical analysis. Comments from Bernard Housen and Cor Langereis helped us improve the presentation of the ideas in this manuscript, particularly those related to paleomagnetic data. This material is based upon work supported by the National Science Foundation under NSF-EAR 1151851 (Titus).

Funding Information:
The paleomagnetic data are listed in the Supporting Information. For their assistance in the field and good humor under all sorts of weather conditions, we thank Willa Rowan and Ella Fadely. We gratefully acknowledge Thor from the Guesthouse Sigtun in H?sav?k who assisted with on-site logistics. Our paleomagnetic processing at the IRM would not be possible without the amazingly kind staff, especially Dario Bilardello and Mike Jackson. We thank Kristj?n S?mundsson and Andy Poppick for helpful conversations about the geology of Iceland and statistics, respectively, although any mistakes in our approach and interpretations are our own. We also thank Seth Waag-Swift for drafting the regional geologic map and uncovering a late-stage error in our statistical analysis. Comments from Bernard Housen and Cor Langereis helped us improve the presentation of the ideas in this manuscript, particularly those related to paleomagnetic data. This material is based upon work supported by the National Science Foundation under NSF-EAR 1151851 (Titus).

Publisher Copyright:
©2018. American Geophysical Union. All Rights Reserved.

Keywords

  • Iceland
  • off-fault deformation
  • paleomagnetism
  • regression
  • transform fault

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