SEDIMENTOLOGICAL ANALYSIS OF DIATOMACEOUS SEDIMENT IN ŞELMO FORMATION OUTCROPPING AT SOUTH OF ADIYAMAN (TURKEY)

Late Miocene Şelmo Formation deposited in relation with the Southeast Anatolia Thrust Belt and the Adıyaman fault zone has well exposed outcrops around the city of Adıyaman in south east of Turkey. Sediments of the Şelmo... [ view full abstract ]

Late Miocene Şelmo Formation deposited in relation with the Southeast Anatolia Thrust Belt and the Adıyaman fault zone has well exposed outcrops around the city of Adıyaman in south east of Turkey. Sediments of the Şelmo Formation in the study area were classified into three members. The Tırpal Member is represented by conglomeratic facies of braided river sediments deposited in front of thrust belt as result of regional uplift in relation to thrust fault. The Alut Member was characterized by marl, marl with fine sandstone interbeds and sandstone of lacustrine deposits. The Kahta Member comprises alluvial and fluvial facies. There is a 3 to 5 meter thick diatomacous level within the Alut Member outcropping in an area of 2 km2 at SE of Bağpınar village, approximately 17.5 km to the city center of Adıyaman (Turkey).
17 species belonging to 10 genera were identified; Cyclotella iris Brun & Heribaud, 1893; Cyclotella iris var. cocconeiformis Brun & Heribaud, 1893; Cyclotella iris var. ovalis Brun & Heribaud, 1893; Ellerbeckia kochii (Pantocsek)Moisseeva, 1992; Actinocyclus krasskei (Krasske) Bradbury & Krebs 1995; Actinocyclus makarovae (Temniskova & Ognjanova) Temniskova & Ognjanova 1992; Actinocyclus sp. 1; Aulacoseira ambigua (Grun.)Simonsen, 1979; Aulacoseira granulata (Ehr.)Simonsen, 1979; Fragilaria bituminosa Pantoscek, 1889; Fragilaria brevistriata Grunow, 1885; Fragilaria pinnata Ehrenberg, 1843; Cavinula scutelloides (W.Sm.); Eunotia diodon Ehrenberg, 1837; Cymbella leptoceros (Ehr.)Kutzing, 1844; Epithemia adnata (Kutz.)Brebisson, 1838; Hantzschia amphioxys(Ehr.)Grunow, 1880. Diatoms are belong to freshwater flora and mostly in planktonic form, but there are a few periphytic (epiphytic) forms. Extinct species accounted for 42.2 % of the total flora. Except one boreal species , Cyclotella iris Brun & Herib. , all identifed species represent the cosmopolitan geographical distribution.
Carbonate content of diatomaceous sediment increase from bottom to top which points deepening of lake and lowering terrigenous input. SiO2 content of marly level also increases upward. Increase in the middle part is due to high diatom content and increase at the upper part is due to increase in clay content. Ba content is higher in diatomaceous level than non diatomaceous levels. There is no systematic changes in trace and rare earth element contents.
Lacustrine facies of the Alut Member of the Şelmo Formation was deposited in a oligotrophic to eutrophic freshwater lake which was neutral to slightly alkaline and the temperature regime was similar to the lakes of the moderate latitudes.