Mechanical compaction and quartz cementation are the most important diagenetic controls on the reservoir quality of the Late Carboniferous - Early Permian fluvio-deltaic Tirrawarra Sandstone in the Cooper Basin of South Australia. The magnitude of these two diagenetic events is controlled by the miner alogical composition of the sandstones. Assuming that the Tirrawarra Sandstones have a common provenance, the nature of the environments in which these sediments were deposited is the principal factor controlling the composition of the framework grains in the unit. Thus, the percentage of rock fragments decreases, and the relative quartz content increases, from the medial part of a braid-delta to point-bar and aeolian environments. The content of ductile rock fragments controls the degree of compaction and the development of quartz overgrowths.