Surface textures of heavy mineral grains from the Palaeocene of the central North Sea

Scanning electron microscopy has revealed both mechanically and chemically produced surface textures on heavy mineral grains from Palaeocene sands of the central North Sea basin. Chemical activity initially modified irregular surfaces, producing mamillae. Further solution produced regular facets, the dimensions of which increase with intensity of etching. Variations in composition of the connate waters are thought responsible for slight variations in etching style. Mechanically-produced surface features similar to those seen on quartz grains, including breakage blocks, V-shaped indentations, grooves, upturned cleavage plates and conchoidal fractures, mostly originated in a pre-Palaeocene phase of sedimentation. The possibility of retention of preexisting surface textures on grains during the sedimentation process must therefore be considered when using such textures in palaeoenvironmental interpretation.