Stratigraphy of the Upper Cretaceous and Paleogene in Yığılca-Bolu (NW Turkey)

Year 1986, Volume: 107 Issue: 107, 1 - 23, 01.12.1986

Orhan Kaya Atife Dizer İzver Tansel Sacit Özen

Abstract

The post-Triassic rocks of the
Yığılca area extend in age from late Santonian/early Campanian to Ypresian or
probably Lutetian, and constitute a marine sequence intervened by submarine and
subaerial unconformities. The sequence is represented primarily by
volcaniclastic sandstone and conglomerate, derived from a provenance of mafic
volcanic rocks, and subordinately by epiclastic sandstone. The Cretaceous and
Paleogene rocks of the Yığılca area have a marked lithic and sequential
similarity to those in the northerly-lying Ereğli area. The Cretaceous is
suggested to have been deposited by the progressive onlap of an apparently
southward transgressing sea. The coeval but differing rocks of the uppermost
Cretaceous and Paleogene in the Yığılca, and southerly-lying Bolu and Mengen
areas, suggests a structural divide to the south of the Yığılca area, formed by
the latest Cretaceous. The totally 200 m thick Cretaceous olistostromal
interval of the Yığılca sequence, which has a 4 m thick correlative in the
Ereğli sequence, has apparently a significant bearing on the stratigraphy of
the so-called «Ankara melange». The arcal structure is characterized by a
southward recumbent syncline whose northern limb is thrusted on the southern.
High-angle faults are suggested to be originally shear fractures related to a
nearly northeast-trending horizontal acute bisector, and later to have acted as
extensional. High-angle faults postdate the thrust, and both are probably
post-Lutetian in age.

Keywords

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