Abstract
The basins in the Marmara Sea are the products of a superimposed evolutionary history defined by two different-aged fault systems: the early Miocene-early Pliocene Thrace-Eskişehir Fault Zone and its branches, and the late Pliocene-Recent North Anatolian Fault and its branches. The Thrace-Eskişehir fault and its westward branching secondary fault systems define the early neotectonic signature in the region. The late neotectonic period started at the end of the early Pliocene when the North Anatolian Fault divided the Thrace-Eskişehir fault into four parts. During the late neotectonic period, the North Anatolian Fault extended westward as a number of splays by joining with the Ganos, Bandirma-Behramkale and Manyas-Edremit Fault Zones. The branches of the North Anatolian Fault Zone (NAFZ) caused the evolution of a number of basins, which differ in character depending on the trend and past characteristics of the older branches that became connected. Since the northern branch of the North Anatolian Fault is connected to the N80°E-trending Ganos Fault Zone (GFZ) in the west, a single buried fault has developed in the Marmara Sea, causing the well-known troughs and ridges, superimposed onto the negative flower structure formed by the GFZ in the early neotectonic period. The middle strand, which extends from Iznik Lake to Bandirma, is oriented east-west up to the N60°E-trending Bandirma-Behramkale Fault Zone, then turns southward in the vicinity of Bandirma, forming a region dominated by compressional tectonics. This bending caused N30°E-trending tension in addition to the strike-slip motion between the eastern part of Gemlik Bay and Bandirma Bay. The southern branch of the NAFZ, on the other hand, produced three pull-apart basins with different characteristics along the Yenişehir, Bursa and Manyas segments. The southern branch of the NAFZ connected to the Manyas-Edremit Fault Zone, which is oriented N45°E to the south of Manyas, and the associated bending and rotation caused a N15°E-trending extension in addition to the strike-slip regime between Manyas and Uluabat. The branches of North Anatolian Fault cut through the Thrace-Eskişehir fault at three places: the East Marmara Sea region, in Gemlik Bay, and to the east of Bursa, giving lateral offsets of 58-59, 7-8 and 10-11 km, respectively. The cumulative motion is 75-78 km, corresponding to the total lateral offset of the North Anatolian Fault in the region. The correlation of these offsets with Global Positioning System slip vectors and with stratigraphic results implies that the North Anatolian Fault reached into the Marmara Sea region about 3.5 million yr ago. Tectonic processes forming the Marmara Sea and its environs were initiated by the Thrace-Eskişehir fault and its splays have been most recently controlled by the North Anatolian Fault and its splays during the last 3.5 million yr.
| Original language | English |
|---|---|
| Pages (from-to) | 493-529 |
| Number of pages | 37 |
| Journal | Marine Geology |
| Volume | 190 |
| Issue number | 1-2 |
| DOIs | |
| Publication status | Published - 15 Oct 2002 |
Funding
This paper was written when the author was a visiting scientist at the Memorial University of Newfoundland. Research funds are acknowledged from the Natural Sciences and Engineering Research Council of Canada (Marmara Sea Gateway Project). Thanks are due to Aksu, Hiscott and Calon for the shallow Seismic Lines. The author is also indebted to Mehmet Sakınç, Fazlı Y. Oktay and Cengiz Tapırdamaz, who have accompanied his studies in the Marmara Sea region since 1990 and contributed to the results presented here. Further thanks are due to Bedri Alpar, who was the first researcher suggesting the author to combine marine geological and geophysical data with those observed on land and his immense data sets of shallow seismic data collected mainly after the 1999 earthquake. Thanks are due also to the Marine Geology reviewers Jeremy Hall and Erdin Bozkurt for their helpful suggestions and to Aral Okay who was the first to propose the study on the GFZ, leading to this paper, and provided conventional seismic sections collected by the MTA. Finally, the author likes to thank his wife Kezban Saki-Yaltırak, who is responsible for the C.E.P. Foundation, which sponsored all his investigations.
| Funders | Funder number |
|---|---|
| Marmara Sea Gateway | |
| Natural Sciences and Engineering Research Council of Canada |
Keywords
- Marmara Sea
- Neotectonics
- North Anatolian Fault
- Sub-basin
- Superimposed tectonics
- Thrace-Eskişehir fault