Sedimentation rate and pattern of Lake Eber hosted in a seismically active basin, central Anatolia, Turkey
by
Özden Ileri
Ankara University Engineering Faculty, Department of Geological Engineering, 06100 Besevler ANKARA TURKEY
Coauthors: Nizamettin Kazanci (Gebze Yüksek Teknoloji Enstitüsü, Mühendislik Fakültesi, Gebze KOCAELI)

Lake Eber is a fresh-water swamp with a surface area of 125 km2 in the Akarcay Basin of south central Anatolia. It has a natural connection to Lake Aksehir (with brackish water) which occupies the present depositional center (955 m above sea level) of the host basin. The host Akarcay Basin is a seismically active, NW-SE oriented, ca 100 km long and 25 km wide graben depression. Its drainage area is ca 7500 km2. As it is bordered with very high relief, particularly in the south, basin margins have been covered by many small and large alluvial fans. A long oblique fault to the south, where a devastating earthquake took place on 3rd February 2002, has influenced the development and progradation of alluvial fans probably since Late Neogene. A series of palaeo- and modern shallow lakes, including Aksehir and Eber, have formed along the prolongation of the basin. The Akarcay river is the source of most of the water and some of the sediment coming into the depression from the SW. Sandy gravel terraces (with bivalves) at 1000, 980 and 970 m levels, typically at eastern end of the basin, show that the modern lakes are the remnants of a very large, deep Late Pleistocene lake. The age of the youngest terrace is dated 6500 yrs BC according to C14 dating. It is noteworthy that there is not any terrace around Lake Eber in spite of the presence of pre-Holocene lacustrine muds.

Lake Eber, with a maximum water depth of 1 m, is located in the mid-eastern part of the basin, between Lake Aksehir and Lake Alvar (which was drained artificially). The lake water freezes in winter. Macrophytes, mostly reeds, cover the whole lake area forming emerging muddy islands. Macrophytes have been intensively harvested by local people for paper industry, however, together with the lake's shallowness, the high volume of nutrients transported by the Akarcay river cause an increase of aquatic plants in the lake. Ephemeral streams, coming mostly from the southern margins, carry fine-grained clastic sediments as part of the distal alluvial fans.

Deposition in Lake Eber is like a seasonal alternation of organic and inorganic sediments. Freezing of lake water is one of controlling factors. Cores up to 4 m long taken in and at the margins of the swamp have been studied and many samples were dated by 14C assay. Results show that the average annual sedimentation rate in the mid and late Holocene is 1.46 mm. This is a relatively high value compared to sedimentation rates of other central Anatolian lakes under the same climatic conditions. It is concluded that active tectonism and basin geometry have combined to control lake sedimentation during the Holocene.

Date received: March 20, 2002

Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caiq-85.