EVOLUTION OF THE TRIASSIC CONTINENTAL-MARGIN, NORTHWEST ANATOLIA

The northwest Anatolian basement consists of two distinctly different metamorphic assemblages which were juxtaposed prior to the deposition of Liassic cover sediments. These include the lower and the upper asso ciations. The lower association is mainly represented by Triassic meta volcanic and associated metasedimentary units, together with a slice o f ophiolite. The upper association rests on the lower association with a low-angle thrust fault and is composed of Paleozoic or older schist s, gneisses and phyllites. A transgressive succession begins above the basement with Permo-Carboniferous neritic limestones. These platform type carbonates were disrupted by rifting during the early Triassic. A t the initial phase of rifting, coarse clastics and associated rift ty pe lavas were formed. The rift then evolved into an ocean basin, which closed at the end of the Triassic. The continental margin of the Tria ssic basin underwent regional metamorphism, initially high T/low P, it was followed later by a high P/low T metamorphic phase. During the me tamorphism, the continental margin units were multiply deformed by nor th-directed compressive stress. Later on, unmetamorphosed Triassic suc cessions of the continental margin were thrust northward onto the meta morphosed part of the same continental margin. Thus the Triassic assem blages of northwest Anatolia collectively display the dynamics and var ious structural affects of the deformation recorded in the continental margin and adjacent oceanic unit.