Artic REU Students map complex fault rupture, Ikertooq Shear Zone, West Greenland

Colin A. Shaw, Montana State University
Joseph Allen, Concord University
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Abstract

The Nagssugtoqidian-age Ikertôq shear zone of western Greenland preserves a complex system of pseudotachylyte-bearing faults continuously exposed for at least 34 km along strike across a width of ~10 km. Decimeter- to kilometer-scale mapping of glacially polished outcrops reveals the geometry, kinematics, and lithologic controls on multi-fault earthquake rupture at hypocentral depths in layered, anisotropic rocks. Studetns working with the Arctic REU- Greenland program have produced multi-scale maps of the the complex fault geolometry on Sarfanguit Island. Pseudotachylyte fault-veins are broadly concordant with foliation and define at least six ~200-m-wide zones of linked faults . Outcrop-scale mapping reveals that individual rupture events are recorded by foliation-parallel reverse fault veins (245°/54°) interconnected by strike-slip lateral ramps (273°/72°), consistent with stacked multi-fault rupture. Subsidiary fault sets and fabric heterogeneity in the host gneiss appears to exert significant control on fault geometry and pseudotachylyte distribution. Ongoing mapping by students and faculty of the Arctic REU Greenland project integrates digital outcrop methods and UAV-based photogrammetry with the goal of producing a dataset with potential to resolve rupture architecture at scales ranging from thin section to near seismic observability. We present preliminary structural data and apply qualitative and quantitative models to explain the development of observed patterns in rupture connectivity, lithologic influence on fault geometry, and inferred kinematics.

Session

Deformation in the upper crust