Sedimentology and paleontology with special reference to the ostracoda fauna of Akyatan lagoon(Adana-SE Turkey)

Abstract

Akyatan, a lagoon on the Seyhan-Ceyhdn-Tarsus deltaic plain lies between Karataş and Tuzla approximately 42 km south of Adana. It is elongate, parallel to the shoreline with an inlet providing access to the sea in the sputh east. It is separated from the adjacent Mediterranean by a beach dune ridge fringed with reed beds. The mainland shore is formed of algal flats with thick reed beds where fresh water canals enter the lagoon. Water depths vary 80-100 cm and increase towards the inlet; they vary with the season. The lagoon is floored with silty clays and clayey silts. The uppermost sediments are at least 2620+70 yrs BP (as determined by radiocarbon dating of thin buried peat layer). Water temperatures vary from 11-12 ° C in winter, 18-23 ° C spring to 30 ° C in summer. Salinities vary from 30-45 %o in winter to 9-12 %o in spring (due to the heavy rain and influx of fresh water through canals) to 25-50 %o in summer. pH of the lagoon water varies from 7.5-9. The most extreme conditions are found in the north westerly inner lagoon away from the inlet and fresh water canal influx. A study has been completed of 4 cores (79 samples) along the axis of the lagoon which were collected by G.Evans and N.Görür of Imperial College with help from staff METU and MTA in 1975. 15 Ostracoda species were determined. These species are Cyprideis torosa (Jones), Neocyprideis subulata (Brady), Heterocypris salina (Brady), Eucypris dulcifons (Diebel and Pietrzenuik), Eucypris nsp., Loxoconcha elliptica Brady, Leptocythere lacertosa (Hirschmann), Candona neglecta Sars, Candona angulata G.W.Mueller, Candona (C.) parallela pannonica (Zdlanyi), Darwinula stevensoni (Brady and Robertson), Ilyocypris gibba (Ramdhor), I. biplicata (Koch), Lymnocythere inopinata (Baird), Aurila convexa (Baird), Candona sp. 1, Candona sp.2 Generally, the assemblage was of great abundance and low diversity: In addition, Pelecypoda, Gastropoda, benthic Foraminiferida, and Charophyta also accompany the Ostracoda association. The lagoon supports a rich fish population which is actively exploited and is a valuable site for resident flocks of flamingoes and migrant birds.