Postmagmatic Tectonic Evolution of the Outer Izu‐Bonin Forearc Revealed by Sediment Basin Structure and Vein Microstructure Analysis: Implications for a 15 Ma Hiatus Between Pacific Plate Subduction Initiation and Forearc Extension

Authors

Walter Kurz, University of Graz
Peter Micheuz, University of Graz
Gail L. Christeson, University of Texas Institute for Geophysics
M. Reagan, University of Iowa
John W. Shervais, Utah State UniversityFollow
Steffen Kutterolf, GEOMAR Helmholtz Centre for Ocean Research Kiel
A. Robertson, The University of Edinburgh
Kurt Krenn, University of Graz
K. Michibayashi, Nagoya University
D. Quandt, University of Graz

Document Type

Article

Journal/Book Title/Conference

Geochemistry, Geophysics, Geosystems

Volume

20

Publisher

Wiley-Blackwell Publishing, Inc.

Publication Date

11-20-2019

First Page

1

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Last Page

29

Abstract

International Ocean Discovery Program Expedition 352 recovered sedimentary‐volcaniclastic successions and extensional structures (faults and extensional veins) that allow the reconstruction of the Izu‐Bonin forearc tectonic evolution using a combination of shipboard core data, seismic reflection images, and calcite vein microstructure analysis. The oldest recorded biostratigraphic ages within fault‐bounded sedimentary basins (Late Eocene to Early Oligocene) imply a ~15 Ma hiatus between the formation of the igneous basement (52 to 50 Ma) and the onset of sedimentation. At the upslope sites (U1439 and U1442) extension led to the formation of asymmetric basins reflecting regional stretch of ~16–19% at strain rates of ~1.58 × 10⁻¹⁶ to 4.62 × 10⁻¹⁶ s⁻¹. Downslope Site U1440 (closer to the trench) is characterized by a symmetric graben bounded by conjugate normal faults reflecting regional stretch of ~55% at strain rates of 4.40 × 10⁻¹⁶ to 1.43 × 10⁻¹⁵ s⁻¹. Mean differential stresses are in the range of ~70–90 MPa. We infer that upper plate extension was triggered by incipient Pacific Plate rollback ~15 Ma after subduction initiation. Extension was accommodated by normal faulting with syntectonic sedimentation during Late Eocene to Early Oligocene times. Backarc extension was assisted by magmatism with related Shikoku and Parece‐Vela Basin spreading at ~25 Ma, so that parts of the arc and rear arc, and the West Philippine backarc Basin were dismembered from the forearc. This was followed by slow‐rift to postrift sedimentation during the transition from forearc to arc rifting to spreading within the Shikoku‐Parece‐Vela Basin system.

Recommended Citation

Kurz, W., Micheuz, P., Christeson, G. L., Reagan, M., Shervais, J. W., Kutterolf, S., et al. ( 2019). Postmagmatic tectonic evolution of the outer Izu‐Bonin forearc revealed by sediment basin structure and vein microstructure analysis: Implications for a 15 Ma hiatus between Pacific Plate subduction initiation and forearc extension. Geochemistry, Geophysics, Geosystems, 20. https://doi.org/10.1029/2019GC008329