Palaeostress analysis of Tertiary post-collisional structures in the Western Pontides, northern Turkey


Sunal G. , Tuysuz O.

GEOLOGICAL MAGAZINE, cilt.139, ss.343-359, 2002 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 139 Konu: 3
  • Basım Tarihi: 2002
  • Doi Numarası: 10.1017/s0016756802006489
  • Dergi Adı: GEOLOGICAL MAGAZINE
  • Sayfa Sayıları: ss.343-359

Özet

Fingerprints of the opening of the Western Black Sea Basin and collision of Pontides and Sakarya Continent along the Intra-Pontide suture can be traced in the area between Cide (Kastamonu) and Kurucasile (Bartin) in northern Turkey, along the southern coast of the Black Sea. The Western Black Sea Basin is an oceanic basin opened as a back-are basin of the northward-subducting Intra-Pontide Ocean. Basement units related to this opening are represented by Lower Cretaccous and older units. The First arc magmatism related to this subduction began during Turonian times. Coeval with this magmatism, back-are extension affected the region and caused development of horst-graben topography. This extensional period resulted in the break-up of continental crust and the oceanic spreading in the Western Black Sea Basin during Late Santonian times. During the Late Campanian-Early Maastrichtian period, the Sakarya Continent and Pontides collided and are magmatism on the Pontides ended, After this collision, the Western Pontides thickened, imbricated and developed a mainly N-vergent foreland fold and thrust belt character since Late Eocene-Oligocene times. The palaeostress directions calculated from thrust faults of this foreland fold and thrust belt are 4.6degrees/156.6degrees for sigma1, 6.4degrees/66.1degrees for sigma2, and 83.2degrees/261.9degrees for sigma3. The nature of the imbrication indicates that it was a northward prograding foreland system connected to a floor thrust (detachment) fault at the bottom. Field observations on curved slickenfibres support the theory that the thrust faults of this imbricated structure have transformed to oblique thrusts and strike-slip faults over time.