Constraining sequence stratigraphy in north Australian basins: SHRIMP U–Pb zircon geochronology between Mt Isa and McArthur River

Abstract

Fifty-five new SHRIMP U-Pb zircon ages from samples of northern Australian 'basement' and its overlying Proterozoic successions are used to refine and, in places, significantly change previous lithostratigraphic correlations. In conjunction with sequence-stratigraphic studies, the 1800-1580 Ma rock record between Mt Isa and the Roper River is now classified into three superbasin phases-the Leichhardt, Calvert and Isa. These three major depositional episodes are separated by ~20 million years gaps. The Isa Superbasin can be further subdivided into seven supersequences each 10-15 million years in duration. Gaps in the geological record between these supersequences are variable; they approach several million years in basin-margin positions, but are much smaller in the depocentres. Arguments based on field setting, petrography, zircon morphology, and U-Pb systematics are used to interpret these U-Pb zircon ages and in most cases to demonstrate that the ages obtained are depositional. In some instances, zircon crystals are reworked and give maximum depositional ages. These give useful provenance information as they fingerprint the source(s) of basin fill. Six new 'Ma) at the top of the Isa Superbasin is essentially unconstrained. The integration of high-precision SHRIMP dating from continuously analysed stratigraphic sections, within a sequence stratigraphic context, provides an enhanced chronostratigraphic framework leading to more reliable interpretations of basin architecture and evolution.

Spatial and temporal trends in Precambrian nitrogen cycling: A Mesoproterozoic offshore nitrate minimum

“…These rocks crop out over 145,000 km 2 and have a maximum thickness of about 5000 meters. Their age ranges from 1492+/-4 Ma determined by U-Pb in zircon dating for the basal Mainoru Formation (Page et al, 2000) to Re-Os dates of 1361+/-31 Ma and 1417+/-29…”

Re–Os and Mo isotope systematics of black shales from the Middle Proterozoic Velkerri and Wollogorang Formations, McArthur Basin, northern Australia

“…1; Plumb, 1979). Three main Superbasin phases occurred between 1800 and 1575 Ma (1800-1760Ma Leichhardt, 1740-1690Ma Calvert, and 1670-1575, and were shaped by tectonic processes at a convergent margin on the southern North Australia craton (Myers et al, 1996;Page et al, 2000;Scott et al, 2000;Betts et al, 2003). Intracratonic deformation during the Isa Superbasin phase resulted in enhanced hydrothermal fluid flow along reactivated faults and the formation of the world-class 1650 Ma Mt Isa, 1640 Ma McArthur River, and 1575 Ma Century Pb-Zn-Ag stratiform ore deposits Page et al, 2000;Southgate et al, 2000).…”

Acritarch Evidence for an Ediacaran Adaptive Radiation of Fungi

“…Tappania from the shallow marine facies of the lower Corcoran Formation and shoreface facies of the upper Jalboi Formation of the Roper River Group in the McArthur Basin, Northern Territory (Javaux et al 2010) is bracketed by a U-Pb SHRIMP zircon age of 1492 ± 4 Ma from an ash bed below, and an Rb-Sr isochron age of for 1429 ± 31 Ma on illite in dolomitic siltstones near the top of the succession (Kralik 1982, Page et al 2000. Interpolating between these ages and errors gives 1466 ± 18 Ma for the fossiliferous levels.…”