Plate Tectonics and Geochemical Composition of Sandstones: A Reply

Abstract

The comments of Roser and Korsch (1984) are related to two aspects: (1) their apparent inability to reproduce the results of the discriminant scores as given in table 9 of my paper (Bhatia 1983) and (2) the effect of grain size on the composition of clastic sedimentary rocks. The apparent discrepancy in the discriminant scores is due to their error in calculation. Roser and Korsch (1984) calculated the discriminant scores using the volatile-free averages of the published sandstone suites tabulated in tables 5-8 of my paper. However, the discriminant functions that I developed are based on the actual (non volatilefree) analyses of the sandstone suites of eastern Australia. Thus, the discriminant scores on the published averages given in table 9 of my paper were also calculated using the actual analyses and not the volatile-free analyses. This is mentioned in the text of my paper (Bhatia 1983 p. 620): "Discriminant scores for averages of the published analyses were calculated using the unstandardized function coefficients of table 3 and the actual abundance of element oxide in the average" [italics added]. The actual average chemical analyses and the calculation of the discriminant scores for three of the suites on which significant apparent discrepancies exist are presented in table 1 as examples. In the three cases presented (Aure Trough, Santa Ynez, and the Rhyolitic Sand suites), all the scores agree with those given in Bhatia (1983) and differ significantly from those calculated by Roser and Korsch (1984). The incomplete published analyses certainly posed some problem. Due to the im-