Colour origin of upper cretaceous pelagic red sediments within the Eastern Pontides, northeast Turkey

Characteristic samples of Upper Cretaceous pelagic red sediments from different parts of the Eastern Pontides (NE Turkey) have been 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 limestone, and characterized by abundant planktonic foraminifers. Hematite content ranges from 0.5 to 3.0 wt.%. Electron microscope observations suggest that the hematite pigment has a diagenetic origin. The red colour is due to presence of hematite pigment, and indicates oxidizing conditions during early diagenesis in a relatively deep marine environment.