Tectonic evolution of the northern shelf of the Marmara Sea (Turkey): interpretation of seismic and bathymetric data


Tur H. , Hoskan N. , Aktas G.

MARINE GEOPHYSICAL RESEARCH, cilt.36, ss.1-34, 2015 (SCI İndekslerine Giren Dergi)

  • Cilt numarası: 36 Konu: 1
  • Basım Tarihi: 2015
  • Doi Numarası: 10.1007/s11001-014-9230-z
  • Dergi Adı: MARINE GEOPHYSICAL RESEARCH
  • Sayfa Sayısı: ss.1-34

Özet

This study is based on the geological interpretation of 250 km(2) of multibeam bathymetric data coupled with 300 km of seismic profiles recorded on the northern shelf of the Marmara Sea offshore Buyuk double dagger ekmece and KuA A1/4k double dagger ekmece Lagoons. The sea bottom morphology has a highly chaotic structure at the exit of the Buyuk double dagger ekmece and KuA A1/4k double dagger ekmece lagoons. This chaotic surface structure is controlled by a basin-ridge system lying in the NE-SW direction at the exit of the Buyuk double dagger ekmece Lagoon and by a relatively deep entrance observed at the exit of the KuA A1/4k double dagger ekmece Lagoon. In addition, the linear submarine slope parallel to the shoreline between the Istanbul Strait and the KuA A1/4k double dagger ekmece Lagoon is an important morphological structure of this area. The Istanbul Strait's canyon on the northern shelf of the Marmara Sea and the elevated submarine plain west of this canyon are other important morphological structures observed at the sea bottom. The geologic interpretation of seismic profiles has allowed us to distinguish two seismo-stratigraphic units. The lower one is separated from the overlying units by a seismic sequence having a seismic facies from chaotic to parallel and the top represented by a high amplitude seismic reflector. Since these units get close to the sea bottom rising landwards, they are inferred to be the seaward continuation of the Oligocene-Upper Miocene units widely exposed on land. The upper unit, overlying the acoustic basement, whose parallel internal reflections onlap and downlap on the top of the acoustic basement, is interpreted as a Quaternary basin fill. Two groups of faults have been identified on seismic profiles and identified based on their characteristics in the study area. The first group consists of dip-slip faults trending NNE-SSW. These faults border the western slope of the Bosporus and the NNE-SSW trending basins offshore of the Buyuk double dagger ekmece Lagoon. The second group of faults consists of NW-SE oriented strike-slip faults. These faults have created the linearities in the same direction at the sea bottom. As the result of comparison of these NW-SE-faults to the North Anatolian Fault Zone (NAFZ), this group of faults is likely to have a relation with the NAFZ. Therefore, it is considered that the mentioned faults may be reactivated in the region due to the stress created by the NAFZ.

This study is based on the geological interpretation

of 250 km2 of multibeam bathymetric data coupled

with 300 km of seismic profiles recorded on the northern

shelf of the Marmara Sea offshore Bu¨yu¨kc¸ekmece and

Ku¨c¸u¨kc¸ekmece Lagoons. The sea bottom morphology has

a highly chaotic structure at the exit of the Bu¨yu¨kc¸ekmece

and Ku¨c¸u¨kc¸ekmece lagoons. This chaotic surface structure

is controlled by a basin-ridge system lying in the NE–SW

direction at the exit of the Bu¨yu¨kc¸ekmece Lagoon and by a

relatively deep entrance observed at the exit of the

Ku¨c¸u¨kc¸ekmece Lagoon. In addition, the linear submarine

slope parallel to the shoreline between the Istanbul Strait

and the Ku¨c¸u¨kc¸ekmece Lagoon is an important morphological

structure of this area. The Istanbul Strait’s canyon

on the northern shelf of the Marmara Sea and the elevated

submarine plain west of this canyon are other important

morphological structures observed at the sea bottom. The

geologic interpretation of seismic profiles has allowed us to

distinguish two seismo-stratigraphic units. The lower one is

separated from the overlying units by a seismic sequence

having a seismic facies from chaotic to parallel and the top

represented by a high amplitude seismic reflector. Since

these units get close to the sea bottom rising landwards,

they are inferred to be the seaward continuation of the

Oligocene–Upper Miocene units widely exposed on land.

The upper unit, overlying the acoustic basement, whose

parallel internal reflections onlap and downlap on the top of

the acoustic basement, is interpreted as a Quaternary basin

fill. Two groups of faults have been identified on seismic

profiles and identified based on their characteristics in the

study area. The first group consists of dip-slip faults

trending NNE–SSW. These faults border the western slope

of the Bosporus and the NNE–SSW trending basins offshore

of the Bu¨yu¨kc¸ekmece Lagoon. The second group of

faults consists of NW–SE oriented strike-slip faults. These

faults have created the linearities in the same direction at

the sea bottom. As the result of comparison of these NW–

SE-faults to the North Anatolian Fault Zone (NAFZ), this

group of faults is likely to have a relation with the NAFZ.

Therefore, it is considered that the mentioned faults may be

reactivate