Biogeochemical expression of seafloor processes in the Çanakkale (Dardanelles) Strait, Turkey

ALPAR Ş. B., Ünlü S.

General Assambly of the European Geosciences Union, Austria, 1 - 04 April 2005

  • Publication Type: Conference Paper / Summary Text
  • Country: Austria
  • Istanbul University Affiliated: Yes


Sea floor sediments taken from the Marmara Sea exit of the Canakkale Strait (Dardanelles),
a 62-km long water passage connecting the Aegean and Marmara Seas,
were held to geochemical analyses. On the basis of grids of echo-sounder, 3.5 kHz
sub-bottom profiler, shallow seismic profiles and side-scan sonar mosaics, the asymmetrical
seabed morphology is controlled by discontinuous post Early Pliocene units
which were influenced by tectonic and eustatic activities while the Miocene basement
is controlled by NE-SW trending dextral strike-slip faults. Gas seepages recorded either
at the bottom or in the water column coincides to the areas close to the faults in
the base rock, around the places the acoustic basement almost outcrops and also occasionally
above the channel-fill deposits. Some conical shaped seabed features (early
phase of pockmarks) appearing in groups range in size from 10 to 30 meters in diameter
and are 1-2 m high. Sediment samples indicated a complicated expression of
textural distribution depending on the depositional processes and possible sediment
transportation in the channel. GC/MS analytical technique has reflected some characteristic
signatures of fatty acid, n-alkane (low and high molecular weight) and volatile
compounds (BTEX and C3 benzenes). Some hydrothermal features of sediment, e.g.
sulphur and manganese which are not always encountered in seafloor sediments, reflected
well in the results of the GC/MS analyses. This gives a chance of correlation
of the chemical results with geological and geomorphologic data on this shelf area to
the east of the strait.