Conference:
15ème Congrès Français de Sédimentologie, 13-15 October 2015, Chambery, France, Page 318.
Authors:
Olivier Parize, Stephanie Fleurance, Gregoire André, Delphine Desmares, Franklin H., Kern G., Mantle D., Edwige Masure, Emmanuela Mattiolli, T. Poquet, Speranta-Maria Popescu, T. Scroop.
Abstract:
During Cretaceous times, Australia was the easternmost part of the Gondwana on the southern passive margin of Tethys and the SW accretionary margin of Pacific Ocean. The climate was cold with periods of ice formation, then warmed up as Australia drifted northwards (e.g. Alexander et al., 2006). From the southern Tethys, the Mid Cretaceous marine transgression reached Australia by the northern Carpentaria Basin (CB), going southward to the Eromanga Basin (EB). Coeval to the opening of the Indian Ocean, the maximum transgression was reached during Aptian and provided intracratonic seaways to E, via the Surat Basin, crossing the Tasmanides volcanic trench and to W, via the Canning Basin (e.g. Alexander et al., 2006). According to Bain and Draper (1997), the intracratonic CB is developed onshore, where it covers about 550 000 km2 in NE Queensland, and offshore, within the Gulf of Carpentaria where the sedimentary thickness reaches around 1600 m. It overlies the Jurassic Bamaga Basin and its equivalents and is overlain by the Tertiary Karumba Basin. It is bounded on its western margin by Proterozoic to Paleozoic formations of Mount Isa Inlier and its eastern margin by Coen, Yambo and Georgetown Inliers and connected to the Eromanga Basin by the Euroka Arch, a 300km wide corridor. Few deep drill holes, conducted by the Bureau of Mineral Resources (e.g. Mossman_1: Smart & Grimes, 1971), and field mapping, in monsoonal tropical climate, provided regional descriptions of the Cretaceous infill of this basin and stratigraphic correlations. CB was identified by AREVA Resources Australia Pty Ltd (AREVA) to have potential for sedimentary-hosted roll front uranium deposits. The “Karumba Project” exploration targeted the fluvial to deltaic siliciclastic Yappar Member, the lower part of the Cretaceous Gilbert River Formation (GRF; see Bain & Draper, 1997). This exploration campaign providing new data, leads to unravel the sedimentology and the stratigraphy of the Cretaceous infill at local and regional scales. The transgression appears diachronous and/or set up successive stages between Upper Barremian and Aptian. The transgressive deposits took place on an inherited basement morphology and onlapped the basin margins. This topographic control led to a complex depositional area induced by a network of incised valleys (e.g. high energy fluvial environment of deposition EoD) and possible sub-basins or isolated depressions (e.g. coal/swamp EoD, lacustrine EoD?), interfluves or terraces (e.g. soils and roots). Constrained by new biostratigraphic analysis, the stratigraphic correlations suggest Barremian – Aptian superposed valley systems linked seawards to lowstand deltas, then their tide-dominated estuarine infill was covered by progradational glauconitic fluvial-dominated deposits (Yappar Facies of GRF). A new sequence starts with glauconitic medium to coarse-grained sand- stones (Coffin Hill Facies of GRF) alternating with glauconitic sandy shales (Aptian to Albian Wallumbilla Formation). These biostratigraphic-based correlations suggest that Yappar, Coffin Hill and Wallumbilla could correspond to proximal to distal facies during Barremian-Aptian transgression in CB. The GRF has been confirmed as a first order reservoir for uranium trapping. However, the exploration of the GRF in the Carpentaria Basin was unsuccessful (André et al. 2015).