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Tectonic-Sedimentary Evolution of the North Tethyan Margin in the Central Pontides of Northern Turkey

By
Timur Ustaömer
Timur Ustaömer
Istanbul University Istanbul Turkey
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;
Alastair Robertson
Alastair Robertson
University of Edinburgh Edinburgh, Scotland, United Kingdom
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Published:
January 01, 1997

Abstract

The Central Pontides of northern Turkey is one of the best exposed seg-ments of the southern margin of Eurasia adjacent to the Tethys Ocean, at least from the Paleozoic onward, and its history can be taken as a guide to the tec-tonic evolution of the Pontides as a whole. A number of east-west-trending tectonic units record subduction-accretion and the growth of the south Eurasian margin. The Central Pontides also document Lower Cretaceous lithospheric extension related to opening of the Black Sea during the Late Mesozoic-Early Tertiary and a later active margin and collisional history.

Three time intervals exemplify the tectonic evolution of the Central Pontides. During the Late Paleozoic-Mid-Jurassic, Tethys was subducted northward, with development of an oceanic arc (the Çangaldağ Complex) and rifting of a continental fragment (istanbul and Devrekani units), related to transform and/or active margin processes, to form a back-arc basin system (the Küre Complex and equivalents) in latest Paleozoic-earliest Triassic times. This was followed in the Lower Triassic by collision of a seamount (the Kargi Complex) with the active Eurasian margin, leading to deep burial beneath accreted units, including ophiolitic rocks. This collision possibly triggered collapse of the Küre back-arc basin further north, also in the Lower Triassic. Southward closure of the Küre Basin by the Upper Jurassic finally led to accretion of the entire tectonic stratigraphy to the southern margin of Eurasia during the “Cimmerian orogeny.”

During the Late Jurassic–Early Cretaceous, the recently formed orogen sub-sided, possibly triggered by renewed northward subduction of Tethys, and carbonate platform sedimentation ensued during the Late Jurassic-Early Cretaceous. Crustal extension of the active margin then took place in the Early Cretaceous. The carbonate platform was dissected into half grabens, into which turbidites, debris flows, and olistoliths were shed. Early Cretaceous extension also activated exhumation of high-grade metamorphic rocks in the Central Pontides as a precursor to opening of the Western Black Sea marginal basin.

During the Late Cretaceous-Early Tertiary, the Western Black Sea Basin underwent sea-floor spreading, while the southern margin rapidly subsided, associated with northward emplacement of ophiolites and ophiolitic melange. During the Early Tertiary, the Pontides were sutured to the Anatolides to the south, resulting in south-vergent reimbrication of the Paleotethyan basement, especially in southerly areas, and north-vergent compression near the Black Sea coast.

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Contents

AAPG Studies in Geology

Regional and Petroleum Geology of the Black Sea and Surrounding Region

A. G. Robinson
A. G. Robinson
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American Association of Petroleum Geologists
ISBN electronic:
9781629810782
Publication date:
January 01, 1997

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