Papers by Selin Özağostos
Sedimentary Geology, 2009
During Late Palaeozoic time a wide ocean, known as Palaeotethys, separated the future Eurasian an... more During Late Palaeozoic time a wide ocean, known as Palaeotethys, separated the future Eurasian and African continents. This ocean closed in Europe in the west during the Variscan orogeny, whereas in Asia further east it remained open and evolved into the Mesozoic Tethys, only finally closing during Late Cretaceous–Early Cenozoic.Three Upper Palaeozoic lithological assemblages, the Chios Melange (on the Aegean Greek island), the Karaburun Melange (westernmost Aegean Turkey) and the Teke Dere Unit (Lycian Nappes, SW Turkey) provide critical information concerning sedimentary and tectonic processes during closure of Palaeotethys. The Chios and Karaburun melanges in the west are mainly terrigenous turbidites with blocks and dismembered sheets of Silurian–Upper Carboniferous platform carbonate rocks (shallow-water and slope facies) and poorly dated volcanic rocks. The Teke Dere Unit to the southeast begins with alkaline, within-plate-type volcanics, depositionally overlain by Upper Carboniferous shallow-water carbonates. This intact succession is overlain by a tectonic slice complex comprising sandstone turbidites that are intersliced with shallow-water, slope and deep-sea sediments (locally dated as Early Carboniferous). Sandstone petrography and published detrital mineral dating imply derivation from units affected by the Panafrican (Cadomian) and Variscan orogenies.All three units are interpreted as parts of subduction complexes in which pervasive shear zones separate component parts. Silurian–Lower Carboniferous black cherts (lydites) and slope carbonates accreted in a subduction trench where sandstone turbidites accumulated. Some blocks retain primary depositional contacts, showing that gravitational processes contributed to formation of the melange. Detached blocks of Upper Palaeozoic shallow-water carbonates (e.g. Chios) are commonly mantled by conglomerates, which include water-worn clasts of black chert. The carbonate blocks are restored as one, or several, carbonate platforms that collided with an active margin, fragmenting into elongate blocks that slid into a subduction trench. This material was tectonically accreted at shallow levels within a subduction complex, resulting in layer-parallel extension, shearing and slicing. The accretion mainly took place during Late Carboniferous time.Alternative sedimentary-tectonic models are considered in which the timing and extent of closure of Palaeotethys differ, and in which subduction was either northwards towards Eurasia, or southwards towards Gondwana (or both). Terrane displacement is also an option. A similar (but metamorphosed) accretionary unit, the Konya Complex, occurs hundreds of kilometres further east. All of these units appear to have been assembled along the northern margin of Gondwana by Permian time, followed by deposition of overlying Tauride-type carbonate platforms. Northward subduction of Palaeotethys beneath Eurasia is commonly proposed. However, the accretionary units studied here are more easily explained by southward subduction towards Gondwana. Palaeotethys was possibly consumed by long-lived (Late Palaeozoic) northward subduction beneath Eurasia, coupled with more short-lived (Late Carboniferous) southward subduction near Gondwana, during or soon after closure of Palaeotethys in the Balkan region to the west.
Science of The Total Environment, 2003
This study covers the geochemical investigations on water and stream sediments to evaluate the in... more This study covers the geochemical investigations on water and stream sediments to evaluate the influence from the abandoned Kalecik Hg mine. The groundwater samples (S5, S8, S9, WW10) are neutral, slightly alkaline waters which have pH values varying between 7.3 and 7.5. Electrical conductivity (EC) values of groundwaters for spring samples are low (250-300 mSycm). However, groundwater obtained from a deep well has a higher EC value of 950 mSycm. Hg concentrations of groundwater samples vary between 0.01 and 0.13 mgyl. Hg concentrations of other water samples taken from mining area from surface waters and adits are between 0.10 and 0.99 mgyl. Adit water (A4) collected at the mine has the highest Hg content of 0.99 mgyl and a pH of 4.4. Trace element concentrations of mine water samples show variable values. As is observed only in MW1 (310 mgyl). A4 was enriched in Cd, Co and Cr and exceed the Turkish drinking water standards (Turk Standartları Enstitusu, 1997). Cu concentrations varÿb etween 6.0 and 150 mgyl and are below the Turkish water standards. Mn concentrations in mine waters are between 0.02 and 4.9 mgyl. Only for sample A4 Mn value (4.9 mgyl) exceeds the standard level. Ni was enriched for all of the mine water samples and exceeds the safe standard level (20 mgyl) for drinking water. Of the major ions SO 4 shows a notable increase in this group reaching 650 mgyl that exceeds the drinking water standards. Stream sediment samples have abnormally high values for especially Hg and As, Sb, Ni, Cr metals. With the exception of sample Ss6 of which Hg concentration is 92 mgykg, all the other samples have Hg contents of higher than 100 mgykg. Pollution index values are significantly high and vary between 69 and 82 for stream sediment samples. ᮊ
Geological Society, London, Special Publications, 2000
... Island (Greece). Alastair HF Robertson & Elizabeth A. Pickett 1 Department of Geology... more ... Island (Greece). Alastair HF Robertson & Elizabeth A. Pickett 1 Department of Geology and Geophysics, University of Edinburgh, Grant Institute, West Mains Road, Edinburgh EH9 3JW, UK Alastair.Robertson{at}glg.ed.ac.uk. ...
Uploads
Papers by Selin Özağostos