Provenance of the Ordovician–lower Silurian Tumblagooda Sandstone, Western Australia

Abstract

Detrital zircon U–Pb ages and heavy mineral assemblages provide conflicting evidence of the provenance of the Ordovician–lower Silurian Tumblagooda Sandstone, a fluvial to shallow marine, red-bed succession over 2000 m thick, within the northern Perth and Southern Carnarvon basins in Western Australia. Tourmaline composition indicates a main provenance from interior continental terranes dominated by ‘Li-poor granitoids, pegmatites and aplites’ and ‘Ca-poor metapelites, metapsammites and quartz-tourmaline rocks,’ akin to the Yilgarn Craton to the east of outcrop of the Tumblagooda Sandstone. Other possible source areas include orogens mostly to the south but lack tourmaline analyses for comparison. Taking into account the lack of garnets—a conspicuous component of the adjacent Proterozoic Northampton Inlier—the limited zircon data are compatible with the Albany–Fraser and Pinjarra orogens along the southern and western margins of Australia and/or terranes in or adjacent to East Africa and/or Antarctica, as ultimate source regions with a minor contribution from the Yilgarn Craton, as with other Phanerozoic strata in Western Australia. Whereas the textural and mineralogical maturity of the sandstone could be explained by derivation from such regions, it is more likely that the source was relatively local and that the sediment passed through several phases of reworking. The main source of ilmenite and hematite, by comparison, may have been mafic–ultramafic rocks and/or banded iron formations within the Archean Yilgarn Craton to the east or the Pilbara Craton to the northeast, mobilised by acidic meteoric waters. Iron oxides forming the earliest cements may have been derived from the oxidation of detrital hematite and ilmenite grains concentrated along some bedding laminae or transported in solution from beyond the zone of deposition. Whereas the detrital iron oxides most likely come from the craton to the east of outcrop of the Tumblagooda Sandstone, the sand grains appear to have originally come from a relatively local orogenic source.

KEY WORDS:

• Tumblagooda Sandstone
• Ordovician–lower Silurian
• Western Australia
• provenance
• craton
• fluvial
• shallow marine
• heavy minerals
• tourmaline
• zircon

ACKNOWLEDGEMENTS

We appreciate the support and advice of Roger Hocking, Chief Geoscientist of the Geological Survey of Western Australia and a pioneer in Tumblagooda Sandstone sedimentology. We also thank Gordon Brown and Dan MacDonald (Department of Earth Sciences Dalhousie University) for preparing the thin and polished sections and for help during microprobe analysis, respectively, Peter Haines (Geological Survey of Western Australia) and reviewers, Chris Lewis (Geoscience Australia) and John Veevers (Macquarie University), are thanked for their constructive comments on the manuscript. The project was supported by research grants to Grant Wach and the Basin and Reservoir Lab at Dalhousie University. This paper is published with the permission of the Director, Geological Survey of Western Australia.

Supplementary Papers

Table 1 Grain counts for the Tumblagooda Sandstone: Qt (total quartzose grains) = Qm (monocrystalline quartz >62.5 μm + polycrystalline quartz such as quartzite >62.5 μm) + Qp (polycrystalline quartz such as chert >62.5 μm); F (total feldspar grains); L (unstable rock fragments = Lithics).

Table 2 Chemical composition (wt%) for tourmalines of Tumblagooda Sandstone (samples GSWA 118300: grains 1 to 34 and GSWA 1813266: grains 35 to 68).

Table 3 Tourmaline analyses from Tumblagooda Sandstone, the Capricorn Orogen, Yilgarn Craton and the Pilbara Craton.