Foraminiferal content and depositional environments of marine sediments in Gediz Delta (İzmir-Menemen-Western Turkey)

Sediments and fossil content of Gediz Delta were examined based on the drilling core samples of the W-NW edge YSK-C and E-NE edge and SK-246 drilling. W-SW part of the Delta is represented by terrestrial delta sediments up to 6 meters and shallow marine detritic sediments up to 35 meters in the YSK-C drilling. Terrestrial part consists of a soiled, graveled, muddy and sandy sediment. Marine part consists of bioclast, mud, gravel bearing sands and graveled sand, bioclast bearing mud layers. Bioclasts comprise of echinite, ostracod, gastropod, foramifer, bryozoa and bivalvia. Benthic foraminiferal fauna determinated in the marine levels are represented by 55 bethic, 2 planktonic species. These foraminiferas reflect that the W-SW sequence of the delta, between 8-31m has been occured in marine conditions. In the SK-246 driling core, E-NE part of the delta represented by terestrial sediments 45.5m in thicknes. However it contains marine levels in the 18-19; 23-24; 36-37.5 meters. Terestrial sediments of E-NE part of the delta generally are represented by Neogene pebles, tufas and ashes bearing sandy and limy mud rocks. While the marine levels in 18-19 and 36-37.5 meters consist of ostracod, thiny gastropod and bivalvia bearing limy claystone and limy mudstone. They are represented by gastropod, echinid, bryozoa, bivalvia and foraminifer bearing sandy mudstones in the 23-24m. Mentioned marine level contains a benthic foraminifer fauna. These evidences show that the E-NE part of the delta has been occured in terestrial conditions and It is temporally covered by marine transgression. In aging survey done by ESR method 8-9m is determined to be 11.376 plus minus 67.53 years; 10-11m is determined to be 16.466 plus minus 16.06 years; 24-25m is determined to be 15.344 plus minus 21.15 years; 25-26m is determined to be 19.995 years. This result illustrates that W-SW parts of the delta is always in marine condition between 20000 and 11000 years and it has been in terrestrial condition since the year of 11000. When W-NW edge and layers of E-NE which is still horizontal are compared marine sediments in west part and terrestrial sediments in East part have been interbedded to each other; additionally it shows that terrestrial condition in east part is 20000 years and it might be older.