Structural evolution of Erdek Bay and its surroundings, Turkey


Vardar D. , Yaltırak C., ALPAR Ş. B. , Öztürk K.

General Assambly of the European Geosciences Union 2008, Austria, 1 - 04 April 2008, vol.10

  • Publication Type: Conference Paper / Full Text
  • Volume: 10
  • Country: Austria

Abstract

The marine area covering Erdek Bay and the Marmara Islands on the southern shelf of
the Sea of Marmara, Turkey is placed in a tectonic basin created by the development of
the North Anatolian fault zone controlling the Sea of Marmara and its paleogeographic
evolution totally depends on the tectonics and climatic sea level changes.
Many historical earthquakes accompanied by numerous landslides on the Marmara
Islands and underwater failures on the slopes of the western Marmara trough were
located between the two branches of the North Anatolian Fault zone, and known as
Marmara Island earthquakes. While the northern branch of the North Anatolian fault
zone forms the complex bottom morphologies through the deep Marmara trough, consisted
of basin and ridge chains, the southern branch goes through the southern shelf.
Since the southern branch is much less active than the northern one, the southern shelf
which is characterized by smoother morphology has not been studied sufficiently. But
some recent geophysical studies show that this branch is still active at present. Beyond
its position between two active fault branches cut through by many secondary
faults, the study area is also bordered to the east by the Kapı da^g Peninsula which
displays N-S oriented parallel features such as deep valleys, mountain ridges, and an
isthmus connecting the peninsula to the continent. To the west, the Dardanelles strait
forms a shallow water passage between the Sea of Marmara and the Aegean which is
established about 12k years ago. The seismic sedimentary records of this connection
were defined in a NW-SE directional semi-enclosed basin between the Marmara Islands
and Erdek Bay depending on their unconformities, lap outs and varying internal
reflections. The topmost seismic unit formed during the last transgression period is
characterized by strong and internally parallel reflectors, the second as sub-parallel
and chaotic complex internal reflections, and the third as sub-parallel and wavy internal
reflections. An unconformity between the upper units was delineated along the
study area representing the erosional surface during the last glacial period above the
sea level.