From Extension to Strike‐Slip Faulting Along the Western Continuation of the North Anatolian Fault in the Northern Aegean Sea: Structural, Geochronological and Geochemical Constraints

Abstract The Northern Aegean region preserves a complex deformation pattern shaped by Miocene extension driven by retreat of the Hellenic subduction system, later overprinted by Plio–Pleistocene transtension linked to the westward propagation of the North Anatolian Fault (NAF). Although numerous structural, geophysical and geochronological studies have been carried out in this area, key questions remain unanswered regarding (a) how deformation is partitioned along the western continuation of the NAF, (b) the timing of extension linked to slab rollback and subsequent transtensional faulting related to NAF propagation, and (c) the influence of structural inheritance during strike‐slip reactivation of the older extensional structural grain. The islands of Lemnos and Aghios Efstratios, located between the two principal NAF branches (the North Aegean Trough and the Edremit‐Skyros Trough), offer an exceptional natural laboratory for addressing these questions and for examining how the process zone of a transform plate boundary evolves through time. Our multidisciplinary data set reveals a two‐stage tectonic evolution from the Early Miocene to the present. WNW‐striking extensional fault zones associated with Hellenic trench retreat developed no later than Burdigalian‐Langhian times (∼16 Ma) and remained active throughout the Miocene. The onset of the “Anatolian transtensional regime” occurred in the Pliocene (no later than ∼5.9 Ma), exploiting a crust already stretched and mechanically weakened by earlier extension. This new strike‐slip regime, imparted by the activity of major NE‐trending Anatolian fault branches, generated ENE‐ to NE‐trending right‐lateral and NW‐trending left‐lateral strike‐slip fault zones, and E‐trending extensional fault zones, locally reactivating inherited WNW‐trending Miocene deformation structures.