Structural Development And Control On Stratigraphy And Sedimentation In The Cooper Basin, Northeastern South Australia And Southwestern Queensland
Apak, Sukru N.
Doctor of Philosophy, 1994
University of Adelaide
Intensive study of the structural and depositional history of the Cooper Basin has revealed that the basin is a mildly compressional structural depression in eastern central Australia. The structural evolution of this basin is strongly controlled by northwest-trending and northeast-trending older basement features. Pronounced pre-Permian compressional events are indicated by northeast-trending major structures, the Gidgealpa-Merrimelia-Innamincka and Murteree-Nappacoongee Trends.
Detailed chronostratigraphic facies analysis of the Patchawarra Formation with tight palynological control revealed that two pronounced phases of uplift occurred during the Sakmarian. The major intra-basin highs were rejuvenated during these earth movements as documented by crestal unconformities (Middle and Upper Patchawarra unconformities).
Each event is dominantly tectonic in character, with similar depositional patterns over these highs related to each event. These events are also present in mid-flank areas and basin margins with contemporaneous deposition in deeper parts of the basin.
Structural inversion has been observed over the Moomba/Big Lake and Murteree high areas. Prior to Sakmarian uplifts, the Moomba Field was structurally higher than the Big Lake Field. After these episodes of uplift, the Moomba Field became a depocentre as indicated by thick deposition of later Permian sediments. Late Permian (post-Daralingie) and late-Middle Triassic (post-Nappamerri) uplifts resulted in further rejuvenation of the main trends with significant erosion of strata from the highs and basin margins.
Results from this study show that there is significant potential for future hydrocarbon discoveries within both stratigraphic and combination traps in the Cooper Basin. Various trap styles are closely associated to faults, unconformities and lateral facies changes. Lowside fault closures, onlap plays and unconformity traps are expected to be well developed along intra-basinal highs, basin margins and pre-existing structures. Deltaic sequences comprising shoreline sandstones, distributary and delta mouth bar deposits are also excellent reservoirs which may be well developed in synclinal areas and flanks of intra-basin highs in the Cooper Basin.
More than 700 exploration and development wells, cores and ditch samples, palynological reports and many seismic lines were examined during the study.
Determination of the timing and scale of structural movements during basin development, recognition of unconformities and reconstruction of palaeogeography, were the main techniques to define the history of the Cooper Basin.