Photograph of the month

摘要

Cylindrical columnar jointing in a Late Paleoproterozoic dolerite dyke in the Mountain Tai World Geopark, Shandong Province, China (baddeleyite TIMS U-Pb age of 1621 ± 9 Ma Lu et al. 2008, Geol. Pub. House, Beijing). The columnar joints are usually circular or elliptical in cross-section and have a maximum diameter of 2 m. There are no mineralogical and textural differences between different layers within the columns. The long axes of the columns are near horizontal and orthogonal to the strike of the dyke.