TESTING THE LATE CRETACEOUS KAIPAROWITS-MESAVERDE FLUVIAL CONNECTION: A DETRITAL ZIRCON U-PB AND PETROGRAPHIC PROVENANCE APPROACH

Upper Cretaceous (Campanian) strata of southern and east-central Utah deposited by generally north-draining rivers provide an excellent opportunity to examine the sensitivity of detrital-zircon analysis in detecting long-distance dispersal systems and testing correlations of continental strata. Samples from the Kaiparowits Formation (n=5) of the Kaiparowits Plateau of southern Utah and Mesaverde Group (Neslen, Bluecastle Tongue of Castlegate, Farrer, and Tuscher formations; n=7) from the Book Cliffs north of Green River confirm previous correlations of the Kaiparowits Formation with post-Castlegate Mesaverde strata. Thrust belt-derived sublitharenite and quartzarenite (Neslen and Bluecastle, respectively) lack Mesozoic grains and contain a broad spectrum of Archean (Neslen peak at 2700 Ma), Proterozoic (peaks at ~1700, 1400, 1100, 1000 and 580 Ma) and Paleozoic (peaks at 528 and 413 Ma) grains that record recycling of Proterozoic, Paleozoic and Jurassic sandstones in uplifted thrust sheets. South-derived feldspathic litharenite (Kaiparowits, Farrer and Tuscher) contain Proterozoic grains (peaks at ~1700, 1400 and 1100 Ma) and a diverse population of Mesozoic grains (Triassic-Jurassic peaks at 200, 178, and 150 Ma; Cretaceous peaks at 98, 80, and 76 Ma). Archean grains are rare to absent. The Precambrian grains are consistent with derivation from SW US basement; the Mesozoic grains were derived from magmatic arc rocks of the southwestern US. TuffZirc ages for the six youngest grains from three Kaiparowits samples are statistically indistinguishable from recent SHRIMP ages on bentonitic tuffs at the same stratigraphic horizons (76-74 Ma; Roberts et al., 2005, Cretaceous Research) and TuffZirc ages from the Farrer Formation. Thus, young grain ages and detrital age spectra corroborate petrographic evidence that Kaiparowits rivers connected northward with the river system that deposited the Farrer Formation.