Two point-counting methods for modal analyses of Holocene sands

Two-different point-counting methods of thin-sectioned sands have been argued in evaluating their grain size effects and aims. The traditional method that reflects the dependence of modal composition on grain-size quite differs from the Gazzi-Dickinson method that shows the total independence of grain-size in thin-section analyses. Sets of goals by the two methods do not seem to be the same; the traditional method aims to demonstrate the effect of depositional environments, climates and diagenesis of sediments, whereas the primary target of the Gazzi-Dickinson method is mainly to clarify tectonic settings in provenances.In an attempt to avoid some confusions raised by the two different point-counting methods, we reveal that there will be no significant difference of petrographic data between two methods if we restrict the sand or sandstone samples less than 2.0phi of mean diameter.