Conference:
15ème Congrès Français de Sédimentologie, 13-15 October 2015, Chambery, France, Pages 228-229.
Authors:
Hemon V., Parize O., Franklin H., Freeman D., Martin-Even M., Poquet T., Popescu S.-M., Thomas M.C., Vajda V.
Abstract:
Located in the North Western part of Australia and opened to the Indian Ocean, the NW-SE trending Canning Basin (CB) is the result of successive sedimentary basins infill associated to different geodynamic conditions, from the initial Early Ordovician rifting. Albeit the timing of the sedimentation ranges from Lower Ordovician to Lower Cretaceous, the stratigraphic succession is affected by five tectonic events, defining six basin phases (linked to high subsidence or inversion/uplift). These major tectonic-enhanced unconformities are linked whether to depots-centers, like the Fitzroy-Gregory Trough, or lacuna which could be associated to high erosional vacuity.
The NE edge of CB is bounded by the Paleoproterozoic King Leopold Orogen fold belt (KLO) which displays numerous and wide radiometric anomalies (airborne survey) and conceals U- enriched metamorphic or magmatic rocks. At the end of 70’s, CB was identified by AFMECO, the Australian subsidiary of AREVA, to have potential for sedimentary-hosted roll front uranium deposits. The exploration targets are the siliciclastic reservoirs located along the NE margin of CB downwards to KLO. Conducted by AFMECO, this uranium exploration (summarized by Botten, 1984) revealed some surface anomalies, in particular in Triassic deltaic deposits, and the Oobagooma U-deposit (now Paladin property) hosted within Yampi sandstones, Upper Carboniferous transgressive deposits which could infilled a glacial paleovalley. At the same time, the Myroodah Prospect is discovered by CRAE, in Triassic deposits outcropping in the heart of Myroodah Syncline, in the Fitzroy Trough.
In the 2008-2010 period, an AREVA project generation work updated the interest of exploration targets within Triassic deltaic Erskine Sandstones Formation (ESF). The goal of the“North Canning Project” assessed the uranium potential of Northern part of CB between 2012 and 2014. Based on facies analysis of cores and constrained by a source approach (zircons) and new bios- tratigraphical data, this exploration campaign impacts the sedimentology and the stratigraphy of ESF and their relationships with the underlying Blina Shales Formation (BSF).
ESF constitute separate depositional events from BSF. A Middle Triassic age is confirmed for ESF. Based on facies-based analysis and paleontological datations, two sequences could be now characterised: SlE$, a lower sequence which could be reported to Triplexisporites palyfordii Zone, and a Spathian-Anisian age; SuE, an upper sequence to Staurosaccites quadrifidus Zone, and apossible Ladinian age.
Their organization could be light comparable: a tide-dominated TST, more or less thick and/or glauconitic, and a storm-dominated HST. A wide incised valley fill (IVF), around 20-30 mthick, characterizes SlE TST: its proximal part crops at Erskine Point and its trend is NW-SE, parallel to Fitzroy Trough whereas, northwards, along the Margaret-Laurel Down Terrace, in interfluve realm, SlE TST corresponds to 20-30 cm thick, condensed, glauconitic, bioturbated level. SlE MFS is characterized by acritarchs influx, Veryhachium and Michrystridium. An IVF characterizes also SuE TST but this IVF crops to the North and the paleocurrents suggest a NE- SW trend, towards KLO, before following Fitzroy Trough axis.
Another main stratigraphic result emphasizes fluvial-dominated lowstand deltas, which are expressed in the Fitzroy Trough. These LST are 20-30m thick and appear well developed into fault-controlled high subsidence areas.