3 Advances in Rocky Mountain Paleontology

Monday, 7 May 2007
8:00 AM - 11:30 AM

DETRITAL-ZIRCON AGE POPULATIONS FROM UPPER CRETACEOUS AND PALEOGENE WAHWEAP, KAIPAROWITS, CANAAN PEAK, PINE HOLLOW AND CLARON FORMATIONS, KAIPAROWITS PLATEAU, SOUTHERN UTAH

Paper number: 3-10
Program: SYMPOSIA SESSIONS
Time: 10:50 AM – 11:10 AM

Authors

Abstract

Detrital zircons age-populations in Upper Cretaceous and Paleogene strata from the Kaiparowits Plateau of southern Utah constrain the changes in foreland basin provenance in the transition from the Sevier to Laramide orogenies. The Campanian Wahweap and Kaiparowits formations contain abundant Triassic (220 - 240 Ma), Jurassic (160-180 Ma), and Cretaceous (90-92 Ma and 77-84 Ma) volcanic zircons with a smattering of Proterozoic and Archean grains, reflecting provenance mainly from a complex Mesozoic magmatic source to the southwest. The Capping Sandstone member of the Wahweap Formation contains, in addition, small Paleozoic and Neoproterozoic grain populations (325-350 Ma, 450 Ma, 500-550, 600-680 Ma) likely recycled through thrust-uplifted Mesozoic aeolianites.

Overlying Maastrichtian Canaan Peak, Paleocene Pine Hollow and Eocene Claron samples lie unconformably above a cobble to boulder conglomerate in the lower Canaan Peak Formation, and contain radically different detrital zircon assemblages. Mesozoic magmatic zircons are sparse. Instead zircon populations were derived from Paleozoic and Proterozoic strata exposed in the Circle Cliffs and other Laramide uplifts to the north and east (Schmitt et al., 1991, GSA Sp. Paper 260; Goldstrand, 1994, JSP, v. 62). Zircon age-populations include Archean (2500 Ma), Yavapai-Mazatzal recycled (1600-1900 Ma), anorogenic granite recycled (1400-1500 Ma), Grenville recycled (900-1200 Ma), and scattered Paleozoic to Neoproterozoic (450-700 Ma) grains. Such a distribution reflects recycled zircons derived from a provenance area of lower Paleozoic sandstones.

Research was funded by Escalante-Grand Staircase National Monument contract to Roberts.