Abstract

In this study we examine an Archean granite-greenstone terrane in northeastern Minnesota (USA) to illustrate the application of high-resolution Lidar (light detection and ranging) altimetry to mapping regional tectonic fabrics in forested glaciated areas. We describe the recognition of lineaments and distinguish between tectonic and glacial lineament fabrics. We use a 1-m Lidar derived bare earth digital elevation model to construct multiple shaded-relief images for lineament mapping with sun elevation of 45° and varying sun azimuth in 45° intervals. Two suites of lineaments are apparent. Suite A has a unimodal orientation, mean trend of 035, and consists of short (< 2 km long) lineaments within sediment deposits and bedrock. Suite B lineaments, which are longer (1–30 km) than those of suite A, have a quasi-bimodal orientation distribution, with maximum trends of 065 and 090. We interpret suite A as a surficial geomorphologic fabric related to glaciation, and suite B as a proxy for the regional tectonic fabric. Field measurements of regional tectonic foliation trajectories are largely consistent with suite B lineaments across the study area. Although not all suite B lineaments correlate to mapped structures, our analysis demonstrates that high-resolution Lidar altimetry can be useful in mapping regional tectonic fabrics in glaciated terrane.

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