Lineament characterization and their tectonic significance using Landsat TM data and field studies in the central highlands of Eritrea

Abstract

Lineaments in the central highlands of Eritrea are mapped using various Red–Green–Blue colour combinations and panchromatic Landsat Thematic Mapper (TM) images. Six sets trending N–S, NNE–SSW, NE–SW, ENE–WSW, WNW–ESE and NW–SE are identified in these images. Field studies generally reveal similar orientations. Field and remote sensing studies indicate that most of the lineaments are extensional fractures that correspond to either dikes emplacement or normal faults. Most of these were subsequently reactivated into strike-slip shear fractures. The NW–SE and NNE–SSW lineaments represent dilatational fractures. The NNE–SSW trending lineaments are the oldest. The N–S and WNW–ESE lineaments form conjugate shear fractures and are younger than the NNE–SSW lineaments. These conjugate shear fractures are also older than another set of conjugate shear fractures oriented NE–SW and ENE–WSW. The evolution of all these fractures is attributed to the episodic Red Sea/Danakil rifting because they either displace or locally reactivate the pre-existing late Neoproterozoic structures. Kinematic and dynamic analyses of the two, older and younger, pairs of conjugate strike-slip fractures revealed, respectively, broadly NW–SE and NNW–SSE oriented transpressional stress ( σ 1) with corresponding transtensional stress ( σ 3) oriented NE–SW and ENE–WSW. The analysis further enabled us to trace the continuation of a major Red Sea/Danakil rift-related transform fault into the central highlands of Eritrea.