Date

2021-2-04

Author

Yetim, Suzan Müge

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An integrated sequence stratigraphic study based on well samples and well log data reveals the signals of eustatic sea level change during the Cenomanian-Turonian time interval in Diyarbakır, southeastern Turkey. The depositional model of the Derdere Formation based on detailed microfacies analysis is proposed as the carbonate ramp model consisting of inner ramp (tidal flat, lagoon and shoal), proximal middle ramp, distal middle ramp and outer ramp depositional settings. In the direction of east to west seven wells are selected in order to correlate with the depositional sequences defined in the outcrops of the Derik section. Third-order depositional sequences typical of Cretaceous greenhouse carbonate systems are defined in the wells based on lithofacies, paleontological data and INPEFA log data. Highstand systems tracks contain a greater abundance of grain-dominated shoal lithofacies with various benthic foraminifers while transgressive systems tracks are represented by pelagic facies with high amount of mud dominated lithofacies containing calcisphaerulids and planktonic foraminifers. The deposition of the Derdere Formation is considered to be diachronic since the oldest levels of the formation are still Cenomanian age in the Diyarbakır Region different from the field section measured in Derik, Mardin Region; hence the number of sequences defined in well sections is nine during Cenomanian-Turonian time interval. Carbon isotope studies are conducted to detect C-T boundary and OAE-2 with biostratigraphy, microfacies and INPEFA logs. Oxygen isotope studies are considered as a secondary tool to define sequences and major stratigraphic surfaces and should be used together with other primary tools including microfacies change, INPEFA logs and biostratigraphy. During the early Cenomanian time interval carbonate content increases with the decreasing rate of relative sea level and causes negative δ18O values at the bottom of the Derdere succession. There are some negative shifts on the oxygen isotope curves in Turonian time interval which is explained by the meteoric diagenesis. A model for highstand deposition on the Derdere ramp platform and diaganetic mechanisms generated during sea level fluctuations is proposed. At the time of the deposition of highstand systems tract, facies deposited on the inner ramp depositional setting were subaerially exposed and meteoric water infiltration caused dissolution and dolomitization type diagenetic mechanisms. Cloudy core-clear rimmed dolomite, which is associated with highstand systems tracts and meteoric diagenesis, enhances reservoir quality of the formation whereas dolomitization observed in the transgressive systems tract does not have any constructive effect on the reservoir quality of the Derdere Formation.

Subject Keywords

SE Turkey, Derdere Formation, Sequence Stratigraphy, Reservoir Quality, Eustatic Sea Level Change, 3rd Order Sequences

URI

https://hdl.handle.net/11511/89647

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Graduate School of Natural and Applied Sciences, Thesis