The Permo-Carboniferous Unayzah Group contains several hydrocarbon-bearing reservoirs in Saudi Arabia, where it is subdivided into the Juwayl and Nuayyim formations. The Ghazal Member, which occurs in the lower part of the former, is dominated by fluvio-glacial sandstones, and it is overlain by diamictites, fluvial and lacustrine sediments of the Jawb Member deposited during glacial retreat. This is succeeded by the Wudayhi Member of the Nuayyim Formation, comprising red siltstones and fine grained sandstones deposited in marginal marine-continental environments. The Tinat Member, recognized in the upper part of this formation, mainly consists of continental sediments.Placement of the boundaries between the various members is often challenging, and palynology data are limited due to the generally unfavourable lithologies. For these reasons, chemostratigraphy was employed to produce a robust scheme of high resolution. A total of 1130 core and cuttings samples were analysed by ED-XRF (Energy-Dispersive X-Ray Fluorescence), with data acquired for 50 elements.The scheme is based on variations in the following ‘key’ elements and ratios: Zr/Ti, Zr, Zr/U, Zr/Yb, Zr/Gd and Th/Y. These parameters are largely associated with changes in source/provenance, and the framework comprises a hierarchical zonation of six zones, eight subzones and two divisions.Based on a detailed comparison between the chemostratigraphic, lithostratigraphic and sedimentological data, specific chemozones can be linked to particular stratigraphic members within the Unayzah Group, though only confidently over cored intervals and in sections where members are clearly identified based on GR log trends. Once the associations between chemozone and member boundaries were established, it was then possible to use chemostratigraphy to define member boundaries in sections where this could not be achieved using other techniques. In addition to this, chemostratigraphy enabled correlative boundaries to be recognized within each member of the Unayzah Group, thus adding an additional level of resolution.