IGCP 521 - INQUA 0501 Fifth Plenary Meeting and Field Trip, İzmir, Turkey, 22 - 31 August 2009, pp.26-27
Absolute ages and depositional characteristics of coastal terraces on the Çanakkale Strait (Dardanelles), Turkey
Avcıoğlu M.1, Yiğitbaş E.2, Kıyak N. G.3, Erginal, A.,E.4.
1, 2Çanakkale Onsekiz Mart University, Department of Geological Engineering, Çanakkale, TURKEY 17020
3Işık University, Department of Physics, İstanbul, TURKEY 34398 3 firstname.lastname@example.org
4 Çanakkale Onsekiz Mart University, Department of Geography, Çanakkale, TURKEY 17020 4 email@example.com
Keywords: Coastal terrace, tectonic uplift, optically stimulated luminescence, water exchange
Çanakkale Strait (Dardanelles) is a seaway connection between the Sea of Marmara and the Mediterranean Sea (Figure 1). However, determination of when, where, and how this connection was established has remained recondite. In order to make a quantitative contribution to understand of development of the Çanakkale strait and evolution of the seaway connection between Mediterranean and Marmara Seas, the coastal terraces along the Dardanelles was aged in detail and also their sedimentary and tectonic aspects were studied.
The basement rock sequence of the coastal terrace deposited in the region composed mainly of the latest middle Miocene – early Pliocene clastic and carbonate sediments deposited in a lake – shallow marine environment. The coastal environment is seen to have been established during Pleistocene – Holocene as evidenced by the presence of beach sands. The coastal terrace deposits represent a thin veneer of upper Pleistocene to Recent nearshore and situated at 0-120m elevations within 10 km of the shores of the Marmara sea and Dardanelles.
The coastal terrace sequences are of wide distribution on both sides of the Çanakkale Strait (Dardanelles). These exposures, which mostly locate in the north of the Cape Nara, have been of common interest by the virtue of their key importance in deciphering water exchanges between the Aegean Sea and the Black Sea. Previous studies were basically dependent upon paleontological and geomorphological attributes of these terraces with the exception of a few attemtps of absolute U/Th dating.
In this presentation, we aim to exert depositional characteristics and absolute burial age estimations of the coastal terrace materials in order to contribute to the current debates upon the geomorphologic and neotectonic features of that area. For this purpose, several analogous aspects of exposures were considered, such as level correlations and tectonic uplift rates, litofasies and biofacies attributes, and burial ages. Seven representative terrace sequences were ascertained having regard to their comparable depositional characteristics, such as fossil contents, stratigraphic orders and bedding features. These are İkizlerçeşme (Location 1), Çayırdere (Loc. 2), İyisu (Loc.3), Saltık (Loc. 4), Çardak (Loc. 5), Kaplantepe (Loc. 6) and Gelibolu (Loc.7) terraces. İkizlerçeşme and Çayırdere terrace deposits are located in the east of Cape Nara. The geological and geomorphological characteristics of these terraces are typical. The deposits of these terraces rest over the Neogene mudstone, sandstone and marl. In these localities there are typical deltaic deposits with their forest and topset beddings. The thicknesses are 4 and 8 meters in İkizlerçeşme and Çayırdere respectively. The marine deltaic sediments can be followed along the coastal cliffs between the two terraces. The transition from the marine-deltaic beds to fluvial deposits is very clear. The Kaplantepe terraces, in the other one terrace on the southern coast of Dardanelles, located in the west of Lapseki town. It is composed of sandstone at the base and conglomerate at the top of the succession in totally 8,60 meters. About 1,5 to 4 meters thick oyster-bed, can be easily observed between sandstone and coarse conglomerates, composed of the fossils of ostrea edulis. Gelibolu and İyisu terraces on the northern coast of Dardanelles composed mainly of conglomerates and about 25 and 8 meters thick respectively. The Quaternary conglomerates unconformably lie on marly Neogene beds. They are partly cross-bedded and consist of limestone cemented pebbles, which composed of green sandstones, radiolarites, quartz and altered magmatic rocks. The fossiliferous beds rest on the conglomerates and consist of slightly brown-yellowish colored fairly soft and loose sands.
The ages obtained from these coastal terraces deposits are summarized in figure 1. The results show collectively that the terraces are found in altitudes ranging between 0 m and 20,00 m and consist mainly of fossil shells of mainly Mediterranean origin, polygenic coastal conglomerates and sandstones, which are variable in vertical section. A total of 34 samples extracted for dating of quartz minerals using Optically Stimulated Luminescence (OSL) demonstrated that the depositional ages of terraces ranged between 7,73 ± 0,68 ka and 153,78 ± 10,90 ka, implying a considerable tectonic uplift rates varying between 0,1627 mmyear-1 and 7,2804 mmyear-1 across the studied coast.