ENHANCING OUR UNDERSTANDING OF ANATOLIAN TECTONICS: EVIDENCE OF THE NATURE AND EXTENT OF THE GRECIAN SHEAR ZONE FROM A LINEAMENT ANALYSIS

The northern boundary of the Anatolian plate is defined by the seismically active North Anatolian Fault (NAF), a dextral strike-slip fault extending from the Karliova triple junction in the east into the Aegean Sea in the west, where the faults’ surface expression becomes absent. The NAF is contained within a greater east-west trending, dextral shear zone between the Anatolian and Eurasian plates. This zone widens in the westward portion of the system, complicating the through-going active fault geometry of the NAF as it approaches the Aegean Sea and is assumed to continue across the southern and central portions of Greece as the Grecian shear zone. The shear zone terminates at the Hellenic trench where slab rollback of the subducting African plate beneath the Anatolian plate creates a dominance of extensional features, and expected surface expressions of strike-slip shear are seemingly absent. Tectonically sourced features such as faults and fractures may exert a strong control on topographic patterns by creating pathways for weathering and erosion that can be highlighted with a topographic lineament analysis. To understand the nature and extent of the Grecian shear zone, we compared a detailed lineament analysis of the Aegean region with expected orientations for Riedel shears and shear-associated structures. Lineament mapping was completed using a digital elevation model processed as hill-shades at a 45° vertical sun-angle, better highlighting topographic changes. The azimuthal direction of the incoming solar radiation was rotated at 45° increments, creating a series of filtered images for manual lineament picking. The Gulf of Saros region – known to be within the shear zone and host the NAF – was analyzed to determine a cell size adequate for dividing the lineament data and producing a more detailed interpretation of the shear zone boundaries. At a coarse analysis of the initial lineament data, there is no strong correlation of dominant orientations with Riedel shears and structures in northern or southern Greece. Central Greece depicts some dominant trends corresponding with Riedel shears in the eastern half, but these features lose their dominancy in the western half. We present a more detailed evaluation of the Grecian shear zone and its extent, strengthening our current understanding of Anatolian tectonics.