THE STRATIGRAPHY OF YAMADAG VOLCANIC COMPLEX BETWEEN YESILKALE AND BEKTAS NEW K/AR AGE FINDINGS

This study comprises the stratigraphy of Yamadag volcanic complex between Yesilkale and Bektas villages and the ages taken from this area. In the investigated area, the Late Oligocene – Late Miocene lavas having compositions varying from basalt to dacite and vertical-lateral transitional pyroclastic rocks are considered as Yamadag Group. Yamadag Group consists Delibayirtepe volcanite, Elmaçati volcanite, Besiktepe volcanite, Agcahüyüktepe volcanite, Göldagi volcanite and Akkoyaktepe volcanite from old to young. K/Ar ages taken from the study area changes from 26.6+0.8 Ma to 10.9+0.4 Ma. The oldest volcanites of the area are Delibayirtepe volcanites and crop out Delibayirtepe north of Yesilkale village. These volcanites consisting basalticandesite, andesite and dacite lavas and pyroclastics of calcalkaline character give 26.6+0.8 Ma K/Ar age. This age corresponds to Late Oligocene.The lavas and pyroclastics of calcalkaline character and consisting dark grey, grey, basalt, basaltic trachyandesite, trachyandesite and pyroxene andesite in composition cropping out near Elmaçati, Dereyurt, Kaymak, Aktepe, and Tasli villages area taken as Elmaçati volcanites. The K/Ar age taken from Elmaçati volcanite is 24.3+1.3 Ma . When the age derived and the stratigraphic setting of the unit is considered, Elmaçati volcanite must be Late Oligocene?-Early Miocene in age. The lavas and pyroclastics of alkaline character and consisting basalt and olivine basalt cropping out around Besik Tepe, Ortabayir Tepe, Yoncalik Tepe, Asagikas Tepe, Fatmayurdu region and west of Akkoyak Tepe are considered as Besiktepe volcanites. From the lava cropping out around Basören village south of study area which similar to Besiktepe volcanite an 16.8+0.5 Ma age was taken by Leo et. al (1974) with K/Ar method. According to this data Besiktepe volcanite must have an Early Miocene age. The altered lavas and pyroclastics of calcalkaline character and consisting light grey, grey and sometimes pinkish-grey andesite and dacite cropping out south and around Yesilkale villages as isolated two small domes are taken as Agcahüyüktepe volcanites. Leo et. al (1974) has taken 14.1+0.4 Ma age from Agcahüyüktepe volcanite by K/Ar method. According to this data unit must have an age of Middle Miocene. The lavas and pyroclastics of subalkaline (calcalkaline/tholeitic) character consisting of andesite and dacite cropping out widely around Göldagi, Kizildag, Karsidag, Yanikdag, Kösoglu Tepe and Boztepe are taken as Göldagi volcanites. The eroded and rounded topography for this unit is very characteristic. The fresh parts of the unit is grey while the altered parts are pink and orange. Göldagi volcanite is interfingering with Akkoyaktepe volcanite and has similar chemical character. An age of 10.9+0.4 Ma was taken from Akkoyaktepe volcanite in this study by K/Ar method. Therefore Göldagi volcanite also must have the age of Late Miocene. The rocks of subalkaline (calcalkaline/tholeitic) character consisting andesite, trachyandesite and dacite cropping out arround Akkoyak Tepe, Asarkale Tepe, Kaletepe and Uzunbez Tepe are considered as Akkoyaktepe volcanites. An age of 10.9+0.4 Ma is taken from Akkoyaktepe volcanite by K/Ar method. Therefore Akkoyaktepe volcanite must have an age of Late Miocene.