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Strength and Stress Evolution of an Actively Exhuming Low-Angle Normal Fault, Woodlark Rift, SE Papua New Guinea

Mizera, Marcel and Little, Tim and Boulton, Carolyn and Katzir, Yaron and Thiagarajan, Nivedita and Prior, David J. and Biemiller, James and Smith, Euan G. C. (2021) Strength and Stress Evolution of an Actively Exhuming Low-Angle Normal Fault, Woodlark Rift, SE Papua New Guinea. . (Unpublished)

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Quantifying lithospheric strength is essential to better understand seismicity in continental regions. We estimate differential stresses and principal stress orientations driving rapid slip (~10 mm/yr) on the active Mai'iu low-angle normal fault (dipping 15–24°; at the Earth’s surface) in Papua New Guinea. The fault's mafic footwall hosts a well-preserved sequence of mylonite, foliated cataclasite, ultracataclasite and gouge. In these fault rocks, we combine stress inversion of fault-slip data and paleostress analysis of syntectonically emplaced calcite veins with microstructural and clumped-isotope geothermometry to constrain a syn-exhumational sequence of deformation stresses and temperatures, and to construct a stress profile through the exhumed footwall of the Mai'iu fault. This includes: 1) at ~12–20 km depth (T≈275–370°;C), mylonites accommodated slip on the Mai’iu fault at low differential stresses (>25–135 MPa) before being overprinted by localized brittle deformation at shallower depths; 2) at ~6–12 km depth (T≈130–275°;C) differential stresses in the foliated cataclasites and ultracataclasites were high enough (>150 MPa) to drive slip on a mid-crustal portion of the fault (dipping 30–40°;), and to trigger brittle yielding of mafic footwall rocks in a zone of mixed-mode seismic/aseismic slip; and 3) at the shallowest crustal levels (T<150°;C) on the most poorly oriented part of the Mai’iu fault (dipping ~20–24°;), slip occurred on frictionally weak clay-rich gouges (μ≈0.15–0.38). Subvertical σ₁ and subhorizontal σ₃ parallel to the extension direction, with σ₁≈σ₂ (constriction), reflect vertical unloading and 3-D bending stresses during rolling-hinge style flexure of the footwall.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemData ItemVictoria University of Wellington research archive
Mizera, Marcel0000-0002-6439-0103
Little, Tim0000-0002-5783-6429
Boulton, Carolyn0000-0003-0597-6152
Katzir, Yaron0000-0003-1999-3746
Prior, David J.0000-0002-4653-2112
Biemiller, James0000-0001-6663-7811
Additional Information:License: Attribution 4.0 International. Published Online: Tue, 23 Feb 2021. Marsden Fund grant VUW1310 provided financial support to conduct this research. We are grateful to Hugh Davies (University of Papua New Guinea) and Ian Smith (University of Auckland) for providing field book scans and discussions. We thank Susan Ellis, Samuel Webber, Jürgen Österle, Laura Wallace, Kevin Norton, and Daniel Stockli for field support and discussions. Special thanks go to the many landowners, oral chiefs, elders, and citizens who granted us permission to study their land. We also thank our guides and carriers without whom this work would not have been possible. All structural data from the Suckling-Dayman Metamorphic Core Complex, raw EBSD data of analysed calcite veins and MATLAB codes used in this study can be obtained from the Data Repository (Mizera et al., 2021: Additional information on fault rocks analyzed in this study can be found in the research archive of Victoria University of Wellington (, Mizera, 2019).
Funding AgencyGrant Number
Marsden Fund of the Royal Society of New ZealandVUW1310
Record Number:CaltechAUTHORS:20210224-100118394
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108168
Deposited By: Tony Diaz
Deposited On:24 Feb 2021 18:26
Last Modified:16 Nov 2021 19:09

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