DETRITAL ZIRCON ANALYSIS OF DEVONIAN AND MISSISSIPPIAN SANDSTONES ADJACENT THE STANSBURY UPLIFT, NORTHERN UTAH AND NEVADA

The source of widespread quartz sands on the carbonate-dominated Western Cordilleran margin during the middle Paleozoic has remained enigmatic. The Late Devonian Stansbury Uplift of northcentral Utah is postulated as a significant contributor of recycled quartz to contemporaneous limestones throughout Utah and Nevada. To test this idea, detrital zircon populations were examined using U-Pb LA-ICP-MS at the Arizona LaserChron laboratory from quartz-rich intervals of the erosional remnants of the Stansbury Uplift (the Devonian Stansbury Formation) and the overlying Mississippian Humbug Formation at the northern edge of the Stansbury Mountains, Utah, and from the upper part of the Late Devonian Guilmette Formation in the Pequop Mountains, northeastern Nevada.

The detrital zircon populations in sandstones in the Devonian Stansbury Formation include a small grouping (15%) at 1381 to 1435 Ma, a large population (60%) at 1846 Ma and smaller groupings (less than 10% each) at 1923, 2080, and 2636 Ma. These populations are distinct from the regional Cambrian Tintic Formation, and most likely reflect provenance in uplifted Ordovician quartzites.

The detrital zircon populations in the Mississippian Humbug Formation include a 10% population at 468 Ma, a broad Grenvillean age population (50%) with peaks at 1017, 1951, 1107, and 1152 Ma, a major Mesoproterozoic population (30%) with peaks at 1381, 1461, and 1552 Ma, and no older grains. This may reflect Laurentian provenance from recycled Paleozoic and Neoproterozoic sandstones of the Cordilleran passive margin. The source of the 468 Ma population is not known.

The Devonian Guilmette Formation distribution from the Pequop Mountains resembles the Stansbury age-distribution. It includes a large (40%) 1400 Ma and 1700 to 1900 age-peaks, and a wide range of Archean grains (2700 to 2900 Ma). These age populations may be derived from mixing of sources in subjacent Ordovician quartzites (the >1800 Ma grains) with Laurentian-derived sandstones (the 1400-1500 Ma grains).

Detrital zircon populations from the Devonian units in this study differ from the Yavapai signature found in contemporaneous sandstones of southern Nevada, suggesting that the Stansbury Uplift had only a local effect on the disbursement of quartz in the Late Devonian.