Chemostratigraphy as a Correlation Tool for the Permo-Carboniferous Unayzah Group and Basal Khuff Clastics Member, Central Saudi Arabia

Abstract

Abstract The Permo-Carboniferous Unayzah Group generally lacks high-resolution biostratigraphic control and attempts at regional lithostratigraphic correlation fail, because of large similarities between sandstones encountered throughout much of the Paleozoic section. In this study, we produce correlation workflow for the Permo-Carboniferous Unayzah Group in central Saudi Arabia, trying to define the Unayzah Group–Basal Khuff clastics boundaries based on chemostratigraphic analysis. A total of 1521 core and cutting samples from 15 wells were subjected to inorganic geo-chemical analysis to acquire major and trace elements. A correlation workflow was developed based on specific changes in elemental ratios dealing with glaciogenic, fluvial, eolian, and coarse-grained alluvial sedimentation processes. The workflow was based on changes in the following key element ratios: Zr/Nb, Nb/U, (Rb + Cs)/La, Al/(Ca + Mg + K + Na), (Zr X Hf)/(Nb X Ta), (Zr X Hf)/Nb, and Zr/(Nb X Ta). This study shows that the Ghazal, Jawb, Wudayhi, and Tinat members of the Unayzah Group are well-characterized chemostratigraphically and are associated with distinct chemo-zones, thereby facilitating correlation in the subsurface.