--> --> Sedimentological and stratigraphical analysis of Upper Cretaceous (Late Santonian- Campanian) pelagic successions of Mudurnu-Göynük and Haymana Basins of the Sakarya Continent, Turkey

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Sedimentological and stratigraphical analysis of Upper Cretaceous (Late Santonian- Campanian) pelagic successions of Mudurnu-Göynük and Haymana Basins of the Sakarya Continent, Turkey

Abstract

The Upper Cretaceous (Late Santonian- Campanian) succession from Mudurnu- Göynük basin and Haymana basin in Turkey are measured for detail studies. The study is based on the Sedimentological parameters and interpretation of depositional environment of two sections and to establish the correlation stratigraphy and comparison with global Cretaceous oceanographic events. The two measured stratigraphic sections are composed of Late-Santonian-Campanian red beds overlying by greenish gray to dark gray shale with occasional intercalation of parallel to cross laminated fine grained sandstone and siltstone and capped by turbiditic sequences and volcanogenic clasts at the top of succession. The lower contact of Haymana section represents unconformity with sedimentary mélange. Microscopic and petrographic studies are carried out in order to identify the microacies. A variety of lithofacies are identified, including radiolarian packstone, silty marl, marls, shaly mudstone, clayey shale, siltstone and fine grained quartzwacke sandstone/siltstones. The presences of microfossils within the thin sections such as globotruncana, globigerina, other planktonic foraminifera, inceramus fragments, sponge spicule, siliceous and calcareous radiolaria and lesser amount of benthic, bivalve and echinoidea. The grains are mostly quartz and other minerals such as feldspar, plagioclase, gluaconite, mica, sericite, volcanic clasts, heavy mineras and association of random distribution of pyrite, pyritized fossils, phosphate and hematite but phosphate clasts are rarely observed in the Haymana section. The observed sedimentary structures are parallel to cross lamintations, symmetrical ripples and few microscopic bioturbation. The depositional environment has been interpreted as Upper Santonian red beds represent transgressive phase of sea level in pelagic environment with oxic condition and then followed by variable dysoxic/anoxic deep marine environment with increasing minor organic carbon content in Campanian with occasional pulses of turbiditic currents/bottom water currents at the top. The bioturbation in the sections may be local occurrence of oxic horizons and/or fluctuation of anoxic to oxic deep marine environment during the deposition. Oxic to anoxic environment change in the same age but in different basins can be caused by tectonic and oceanographic changes.