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Reliable and precise ages of Quaternary pedogenic carbonate can be obtained with Th-230/U dating by thermal ionization mass spectrometry applied to carefully selected milligram-size samples. Datable carbonate can form within a few thousand years of surface stabilization allowing ages of Quaternary deposits and surfaces to be closely estimated. Pedogenic carbonate clast-rinds from gravels of glacio-fluvial terraces in the Wind River Basin have median concentrations of 14 ppm U and 0.07 ppm Th-232, with median (Th-230/Th-232) = 270, making them well suited for Th-230/U dating. Horizons as thin as 0.5 mm were sampled from polished slabs to reduce averaging of long (greater than or equal to10(5) yr), and sometimes visibly discontinuous, depositional histories. Dense, translucent samples with finite Th-230/U ages preserve within-rind stratigraphic order in all cases. Ages for terraces WR4 (167,000 +/- 6,400 yr) and WR2 (55,000 8600 yr) indicate a mean incision rate of 0.26 +/- 0.05 m per thousand years for the Wind River over the past glacial cycle, slower than inferred from cosmogenic-nuclide dating. Terrace WR3, which formed penecontemporaneously with the final maximum glacial advance of the penultimate Rocky Mountain (pull Lake) glaciation, has an age of 150,000 8300 yr indicating that it is broadly synchronous with the penultimate global ice volume maximum. (C) 2003 Elsevier Science (USA). All rights reserved.