Strength and Stress Evolution of the Active Mai'iu Low-Angle Normal Fault, Data Repository
Description
Quantifying lithospheric strength is essential to better understand seismicity in continental regions. In the manuscript “Using Syntectonic Calcite Veins to Reconstruct the Strength Evolution of an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea”, we estimate differential stresses and principal stress orientations that drive rapid slip on the active Mai’iu fault (dipping ~16-24° at the Earth’s surface) in Papua New Guinea. We compile stress-depth snapshots by taking advantage of space-for-time relationships provided by progressive slip localization within the cooling and exhuming footwall of the Mai’iu fault. Estimated differential stresses are based on the mechanical twinning and/or recrystallized grain-size of deformed calcite veins that cross-cut the sequentially formed fault rock units (mylonites, foliated cataclasites, ultracataclasites and gouges). The orientation of principal stresses acting on the fault zone are estimated using stress-inversion techniques on crystallographic data for calcite-twins collected by electron backscatter diffraction (EBSD), and on fault-slip data of late outcrop-scale brittle faults cross-cutting the footwall and hangingwall of the Mai’iu fault. The data repository provides the raw dataset used for the paleostress analyses in this study from which we derive the fault’s peak strength (140–185 MPa) and the integrated strength of the extending brittle crust. The raw dataset includes: (1) Calcite E-Twin Analysis: 12 subfolders with EBSD data on the analyzed calcite veins (.cpr, .crc), overview maps (.jpeg) of all analyzed calcite grains, excel-sheets with orientation and twin morphology data on the analyzed calcite grains, and EBSD Euler conversion output files (_out.xlsx; see below); (2) Calcite Grain-Size Piezometer: 8 subfolders with EBSD data on the analyzed calcite veins (.cpr, .crc), multiple overview maps (.png) of the analyzed calcite veins, and grain-size histograms of the relict and recrystallized grains; (3) Calcite Paleostress Analysis: twinning data that was made analogous to fault-slip data (.fdt) and best-fit stress orientations as calculated by the multiple inverse method (.mi4); (4) EBSD Euler Conversion: MATLAB code to calculate slip plane (e-plane) and glide direction from calcite host-twin pairs and to transform EBSD acquired orientation data from a sample reference frame into a geographic system; (5) Mai'iu Fault Structural Data: an excel-sheet with all structural data collected in the Suckling-Dayman Metamorphic Core Complex during the field campaigns in 2014, 2015 and 2016 (includes sample locations, fault-slip data, bedding data of the Gwoira Conglomerates, etc…; version 7, date: 26.09.2016). All geothermometric data and explanations on how to reproduce the estimated paleostresses (using the provided raw dataset) can be found in the main manuscript. This unique dataset provides insights into the strength and stress evolution of the Woodlark Rift, Papua New Guinea.