Preliminary Geologic Interpretation of SAR Data, Yellowknife-Hearne Lake Area, N.W.T.

Abstract

Airborne, narrow swath, C-band synthetic aperture radar (SAR) imagery, obtained from the Yellowknife-Hearne Lake area, essentially reflects the geomorphology or landforms of the region. These in turn can be readily related to specific lithologies, rock masses, structure and cultural features. Terrain analysis using textural and tonal (brightness) characteristics of the radar images along with drainage and lakeshore characteristics permitted definition of several lithologic classes: Granite terrain type-1, generally the brightest (lightest) area, has a "coarse" mottled signature, reflecting the hummocky surface characteristic of granites in this area. Metasedimentary terrain is typified by an intermediate tone, a thinly laminated texture reflecting bedding and angular shorelines of some lakes. Metavolcanic terrain is subordinate in area and lacks well-defined textural or tonal characteristics. It is most easily recognized as parallel ridges with little or no curvature. The city of Yellowknife is readily identifiable by its bright signature and rectangular pattern or texture. Lineaments, recognized by the alignment of rivers and shorelines, are greatly enhanced by bright radar reflections from northerly facing cliffs and radar shadow (zero signal return) of southerly facing cliffs. Several major structural lineaments in the area, known from aeromagnetic and geological maps (diabase dykes, faulted contacts, etc.) are readily apparent in the SAR imagery, as are numerous extensions and subsidiary lineaments. Circumstantial evidence suggests that post-Precambrian and neotectonic activity may be related to lineaments.

Key words: synthetic aperture radar (SAR), Yellowknife-Hearne Lake area, terrain analysis, lineaments, neotectonics