Provenance record of a rift basin: U/Pb ages of detrital zircons from the Perth Basin, Western Australia

U/Pb dating of 588 detrital zircons by ion microprobe from Lower Triassic, Permian and lower Paleozoic sandstone samples from the Perth Basin yield ag es ranging from Archean to early Paleozoic. The detrital age spectrum of Lo wer Triassic samples differ from underlying units in lacking Archean and po st-Mesoproterozoic detritus. The Archean Yilgarn craton has previously been envisaged as the main source of detritus in the Perth basin, The bulk of t he detritus, however, is of Mesoproterozoic age, which together with the ov erall broad spectrum of age ranges within individual samples indicates that the detritus was derived from multiple sources. Potential source regions r ecognized include the Yilgarn craton, the Mesoproterozoic Albany Fraser Oro gen, the Meso- to Neoproterozoic Leeuwin complex of the Pinjarra orogen, an d probably also the late Mesoproterozoic Northampton complex of the Pinjarr a orogen. In addition, source terranes possibly associated with Greater Ind ia and East Antarctica, which originally formed the western and southern ma rgins of the basin, may have also contributed detritus accounting for the i nput of material whose age cannot be related to the known age ranges in cur rently exposed bounding source blocks. The multi-sourced nature of the detr itus suggests the Perth basin was not a simple half-graben structure down s tepping to the west but contained a variety of uplifted blocks with an over all longitudinal supply of detritus from the south. The distribution of exp osed source blocks changed dramatically at the start of the Triassic with t he cessation of input from Archean and Neoproterozoic source regions. The d iffering age spectra between Triassic and Permian strata and between Late P ermian and older sequences suggest any reworked detritus is of extra-basina l origin and not related to intra-basin erosion of underlying rock units. P otential sources for this reworked multicycle detritus are the metasediment ary sequences within the bounding source terranes. (C) 2000 Elsevier Scienc e B.V. All rights reserved.