Colour genesis of Upper Cretaceous pelagic red sediments within the Eastern Pontides, NE Turkey

In the Eastern Pontides (NE Turkey), Upper Cretaceous pelagic red sediments have a great lateral extent with remarkable colour, lithology and thickness of up to 45 m. Their geographical distribution represents two distinct zonations similar to the tectono-sedimentary division from north to south. In this study, characteristic samples of the pelagic red sediments from different parts of the Eastern Pontides were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy coupled with energy dispersive analyses (SEM-EDAX). The red sediments are composed of limestone and muddy (silty and argillaceous) limestone, and characterized by abundant planktonic foraminifers. Hematite was detected in the all samples and its content ranges from 0.5 to 3.0 wt %. Electron microscope observations suggest that the hematite pigment has a diagenetic origin.The red color is due to the presence of hematite pigment, and indicates oxidizing conditions during early diagenesis in a relatively deep marine environment