Article Details
NEOGENE STRATIGRAPHY OF THE İZMİR -OUTER- BAY ISLANDS
Indexed In
Volume 152 / 2016Authors:
Fikret GÖKTAŞKeywords:
Gulf of Izmir, Neogene Stratigraphy, Middle Miocene Deposition, Alkaline Basic Volcanism, K/Ar GeochronologyAbstract:
The volcaniclastics, derived from calcalkaline acidic-intermediate volcanism in the region during late Early Miocene, and lacustrine deposits of Middle Miocene and alkaline volcanics are exposed on Uzun Island, Hekim Island, Çiçek Islands and Karantina Island in the Outer Gulf of Izmir. Kocadağ volcaniclastics derived from Kocadağ volcanism, by extruding mainly calcalkaline andesitic-dacitic products during late Early Miocene, represents the exposed oldest rock unit. The volcaniclastic succession extending in the north of Uzun Island is composed of pyroclastics in ignimbrite and blocky ash flow facies, and epiclastics in volcanic mass flow (lahar) facies. Foça tuff, represented by rhyolitic ignimbrites, originated from an area around Foça Peninsula and moving to an area around Uzun Island, emplaced onto the Kocadağ volcaniclastics in two main explosive stages. The Değirmentepe member alluvial deposits composed of coarse volcanic detritus were deposited during a inactive period between the explosion stages. A K/Ar age of 16.0 Ma was obtained from a rhyolite dome, which shows lateral relationship with the correlant ignimbrites in Foça Peninsula, and so it is considered that Foça tuff emplaced onto the region at the end of late Early Miocene. Lacustrine-dominated Middle Miocene succession, which overlies the Foça tuff unconformably, differentiated as the Urla group. Urla group consists of alluvial Beşiktepe formation, the Pırnallı Island volcaniclastics, which is composed of sublacustrine volcanic density-flow deposits and felsic ignimbrites, Hekim Island basalt comprising basic volcanics and lacustrine Urla limestone, respectively from bottom to top. Beşiktepe formation only exposed on Uzun Island, overlies the Foça tuff with an unconformity indicating a basin margin deposition during the Middle Miocene. Pırnallı Island volcaniclastic succession, which its lower boundary does not exposed within the area on Hekim Island and Çiçek Islands, is mainly composed of epiclastics deposited by the dynamics of sublacustrine gravity flow and includes trachytic ignimbrite layers in various welding degrees. The main lithologic components of Pırnallı Island volcaniclastics derived from alkaline trachytic volcanism, which was active during the Middle Miocene in Menteş Peninsula.
