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Detrital zircons from 13 Late Mesoproterozoic to Early Neoproterozoic sandstones and two Palaeozoic sandstones from Tasmania were dated in order to improve constraints on depositional ages, to test correlation between Proterozoic inliers, and to characterise source regions. These include successions considered to be the oldest presently exposed in Tasmania. Typical features of the age distributions of the Proterozoic rocks are prominent data concentrations at 1800–1650 Ma and 1450–1400 Ma, and a minor spread of Archaean ages. Statistical testing of the similarity of the age profiles shows that widespread quartzarenaceous samples from the Detention Subgroup, Needles Quartzite and from the Tyennan region are strongly similar, consistent with broad correlation. Relatively large differences are seen between the Detention Subgroup and the conformable, stratigraphically higher Jacob Quartzite, which contains an additional spread of 1300–1000 Ma zircons suggestive of a Grenvillian source. Age profiles of the quartzarenites and quartzwacke turbidites (Oonah Formation and correlatives) cannot be readily differentiated. The Oonah Formation likewise includes samples with and without Grenvillian ages, and there is no 750 Ma zircon population that would be expected if the turbidites were genetically related to the Wickham Orogeny. The simplest interpretation is that the quartzarenites (Rocky Cape Group and correlatives) and the turbidites (Oonah Formation and correlates) are lateral equivalents, although a younger (post‐Wickham Orogeny) age for the Oonah Formation cannot be discounted. A maximum age of ca 1000 Ma is inferred for the Oonah Formation, Rocky Cape Group and correlatives. A minimum age of ca 750 Ma is provided by the basal age of the overlying Togari Group and correlatives. In a metasediment from western King Island, the youngest detrital zircons are ca 1350 Ma, allowing a pre‐Grenvillian depositional age as suggested by previous dating of metamorphic monazite. However, the age profile of this sample is not dissimilar to the other Tasmanian successions that are inferred to be 1000–750 Ma. The Wings Sandstone, of southern Tasmania, contains an unusual profile dominated by Grenvillian ages, consistent with an allochthonous origin. Basement ages that broadly match the age spectra of the Tasmanian Proterozoic sediments are found in southwestern Laurentia, consistent with mutual proximity in Rodinia reconstructions. The Palaeozoic sandstones, from the turbiditic Mathinna Supergroup of northeastern Tasmania, have zircon age profiles typical of the Lachlan Fold Belt, with a predominant latest Neoproterozoic–Early Cambrian component and a lesser, broad Proterozoic data concentration at ca 1000 Ma. Western Tasmania was not a significant part of the source area for these rocks.

A new compilation of magnetic data over onshore and offshore Tasmania plus existing geological mapping and gravity data has provided the basis for the production of a map illustrating the geometric distribution of the main basement units that comprise Tasmania Significant items of the new interpretation map include the delineation of the widespread sub-surface granite occurrences in Tasmania, identification of more extensive occurrences of Proterozoic rocks than previously known, mapping of the extent of the Dundas Trough and extensive northwestern and southeastern continuations of the Beaconsfield ultramafics, definition of the areal distribution of Mesozoic sedimentary basins and the control of Proterozoic lineaments, in particular the Arthur Lineament, on the development of the Mesozoic basins. The use of filtering techniques to suppress the magnetic effects of shallow magnetic sources proved particularly valuable for mapping deeper structures obscured by basalt flows and dolerite dykes and sills.

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