MICROFACIES ANALYSIS OF THE CRETACEOUS/PALEOGENE BOUNDARY IN THE HAYMANA BASIN, CENTRAL ANATOLIA, TURKEY

An integrated sedimentological and paleontological study was carried out across the Cretaceous/Paleogene (K/Pg) boundary in the Haymana Basin, Central Anatolia, Turkey. A 29.41-m-thick section consisting of limestones and marls were divided into five planktonic foraminiferal biozones; Planoglobulina acervulinoides, Racemiguembelina fructicosa, Pseudoguembelina hariaensis for the Late Maastrichtian; Zones P0 and P1a for the Danian. A detailed microfacies (MF) analysis was conducted spanning the K/Pg boundary to evaluate the depositional history of the area. Ten MF types were determined based on mineralogical components, macro-, and microfossil assemblages, and texture of the samples observed in thin sections and outcrop. Major fossil groups like planktonic foraminifera, hyaline and agglutinated large and small benthic foraminifera, mollusks, echinodermata, bryozoa, calcareous red algae, and calcispherulids were used as biogenic constituents in the MF interpretations and their stratigraphic distribution was determined. The MF indicate that the deposition took place on a carbonate shelf to an open marine environment. The section begins with an alternation of bioclastic packstones (inner shelf to slope), grainstones (platform interior to open marine), wackestone-packstones (shelf to slope), and bivalved floatstones (slope) with large benthic foraminifera and calcareous red algae. Few planktonic foraminifera, bryozoans and fragments of echinoderms and mollusks are also present. The section continues with wackestones with planktonics (deeper shelf to slope), iron-rich silty marls (toe of slope) and quartz-rich silty limestones (slope to basin) with benthic and planktonic foraminifera and calcareous red algae. Towards the K/Pg boundary silty limestones with benthic and planktonic foraminifera (slope to basin) were deposited. The boundary beds are rich in clay minerals like smectite and chlorite similar to many other K/Pg boundary sections in the world. In the early Paleocene, silty limestones with planktonic and benthic foraminifera were deposited. Our facies model suggests that carbonates deposited in the lowermost and uppermost parts of the section represent a progradation stage during a highstand shedding and the middle silty marl succession was deposited during a transgression.