New method of structural analysis and measurement of V-shaped percussion cracks in quartz sands surface by confocal laser scanning microscope (CLSM)

Abstract

Microtextures of quartz sand grains can be used to establish sedimentary provenance of sedimentary deposits. V-shaped percussion cracks (Vs), which are randomly produced by grain-to-grain mechanical collision in high-energy subaqueous environments, are significant microtextures used for investigation of fluvial and marine sediment. In previous studies, others have used the percentage of microtextures obtained by scanning electron microscope to compare sediment samples. We developed a new method of measurement and evaluation of the surface of quartz grains using a confocal laser scanning microscope (CLSM) and applied the method to coastal sands containing quartz grains with abundant Vs. The method using international-standard surface-roughness parameters (ISO 25178) is useful for evaluating surface textures of quartz grains and for quantifying the structures of Vs (such as aperture area, density, and depth). The results of applying the method to coastal sands suggest that the density of Vs related to the coastal geological setting, that the depth of Vs related to wave height and offshore gradient, and that the size of Vs was not influenced by grain size or mineral composition of the coastal sands. This new method can corroborate preceding methods in provenance study of quartz grains in subaqueous environments. In principle, it also could apply to other types of microtextures and other minerals, such as degrees of weathering on surfaces of heavy minerals. This method, using a CLSM, has the potential to be applied to various provenance studies using grain-surface texture.