RECYCLED ZIRCONS FROM ORDOVICIAN QUARTZITES DEFINE PROVENANCE FOR UPPER DEVONIAN BEIRDNEAU AND STANSBURY FORMATIONS, SOUTHERN IDAHO AND NORTHERN UTAH

The provenance of well-rounded quartzose sandstones in carbonate-dominated Upper Devonian strata in northern Utah has not been identified. Using facilities at the Arizona LaserChron center, we apply detrital-zircon provenance analysis to this problem, and suggest that sandstones in the Beirdneau Formation were sourced in the Stansbury Uplift, which exposed Ordovician Swan Peak Quartzite. Detrital zircons sampled from a 40 m interval of quartzose sandstone in the Upper Devonian Beirdneau Formation in the Malad Range of SE Idaho have the same major zircon age-populations as the Stansbury Formation from the Stansbury Mountains of northern Utah.

In the Beirdneau sandstone, 65% of the detrital zircons are 1800 to 1940 Ma. Smaller populations are present at 1430 to 1450 Ma (7%), 2060 to 2080 Ma (5%) and 2640 to 2740 Ma (17%). Notably absent are Paleoproterozoic grains between 1600 and 1700 Ma, and Grenville-age grains between 950 and 1250 Ma. This age distribution matches that in the Famennian Stansbury Formation sandstone on the northern margin of the Stansbury Uplift with a K-S P-value of 0.847, suggesting that the samples could have been derived from a common source. Previous analyses of the Ordovician Swan Peak quartzite suggest it is the primary source of sand in the Stansbury and Beirdneau formations, with K-S correlations of 0.528 and 0.256, respectively. Grenville-age grains and 1400 Ma grains could have been derived from Cambrian sandstones that were underneath the Swan Peak in the Stansbury Uplift.

The strong provenance linkage between Stansbury and Beirdneau quartzites points to a genetic and temporal correlation of these Upper Devonian formations with the Stansbury Uplift. Their distinctive detrital-zircon age spectrum is absent in Upper Devonian quartzose units of the Guilmette Formation in southern Nevada, suggesting that dispersal of sediments from the Stansbury Uplift was limited to regions in the northern part of the western miogeocline, north of a the Pilot basin and a reactivated east-trending Tooele Arch. Circulation patterns either by longshore or aeolian processes did not transport these sediments southward.