Tectonic Units and Sutures in the Pontides, Northern Turkey

Abstract

The Pontides is made up of three major tectonic units juxtaposed in Mid- to Late Mesozoic times. The Istranca Massif in the west consists of sandstone, quartzite, shale, limestone and Late Permian granitoid deformed and metamorphosed during the, Late Jurassic. Its contact with the Istanbul Zone further east is covered by the Eocene sediments. The Istanbul Zone is characterised by a well developed, unmetamorphosed and little deformed continuous Paleozoic sedimentary succession extending from Ordovician to the Carboniferous overlain with a major unconformity by latest Permian to lowermost Triassic continental red beds. The Intra-Pontide Suture of Late Triassic-Early Jurassic age separates Istanbul and Sakarya Zones. In marked contrast to the Istanbul Zone, the Sakarya Zone does not have a Paleozoic basement; Karakaya Complex of Triassic age made up of strongly deformed and metamorphosed basic volcanic rocks, limestones and greywackes with limestone olistoliths forms the basement to the undeformed post-Triassic sediments of the Sakarya Zone. The Karakaya Complex probably represents a Triassic magmatic arc/forearc/trench complex and may be part of a Cimmerian “Continent”. The Sakarya Zone is separated from the Anatolide-Tauride units by the İzmir-Ankara-Erzincan Suture. The İzmir-Ankara-Erzincan Ocean must have been in existence during the Triassic as no equivalent of the Karakaya Complex has been found south of the suture. Moreover the Tauride nappes include abundant Triassic pelagic sediments and volcanic rocks representing continental margin deposits of Triassic age.