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Sedimentary cyclicity in the upper cretaceous successions of the Haymana Basin (Turkey): depositional sequences as response to relative sea level changes

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2007
Huseynov, Afgan
The Haymana basin in Central Anatolia (Turkey) formed on a Late Cretaceous to Middle Eocene fore arc accretionary wedge. The aim of this study is to investigate the sedimentary cyclicity and depositional sequences in the Upper Cretaceous clastic successions of the Haymana basin. To be able to achieve this objective, a 250 m stratigraphic section, which is mainly composed of siliciclastics has been measured in the Haymana Basin. In this study, detailed lithofacies analyses were performed and five different facies were recognized in the studied interval of the Haymana Formation. Sandstones, shales and conglomerates are the most abundant in the succession. In the measured section, two chronozones were identified based on the biostratigraphic data. These are the lower Dicarinella asymetrica chronozone and the upper Globotruncanita elevata - Globotruncana ventricosa chronozone corresponding to the Upper Santonian and Lower to Middle Campanian, respectively. Sedimentological analyses, such as provenance, palaeocurrent and grain-size sphericity were also performed and their relation with depositonal environment and change in depositional conditions were discussed. In order to construct the sequence stratigraphic framework, detailed lithofacies analyses and their vertical association were carried out. The studied interval of the Haymana Formation represents a prograding submarine fan subdivided into three depositional sequences, each with several tens of meters thick successions and two sequence boundaries. Each depositonal sequence consists of system tracts and turbiditic basic sequences with sandstone and conglomeratic beds overlain by mudstones. Turbiditic basic sequences, the sandstone and mudstone alternation allows distinction of smaller subdivisions, namely, basic cyclic units, which are the building blocks of system tracts and turbiditic basic sequences. Depositional sequences of the studied section of the Haymana Formation may correspond to third order relative sea level cycles. Accordingly, fourth and fifth order (Milankovich) cycles might be proposed as basic sequences and basic cyclic units, respectively.