U-Pb geochronologic analyses were conducted on 44 detrital zircon grains from two samples from Mississippian sandstones of the Inskip and Tonka formations of central Nevada. The Inskip Formation represents the westernmost exposure of clastic strata that accumulated on top of the Roberts Mountains allochthon following mid-Paleozoic emplacement, whereas the Tonka accumulated in a foreland basin inboard of the Antler orogen. This study complements a previous detrital zircon analysis of the Pennsylvanian Battle Formation, a unit that unconformably overlies central portions of the Roberts Mountains allochthon. The main groups of ages in the Inskip and Tonka samples are ca. 1750-2070 Ma. The Tonka Formation also yielded a few grains that are <1.6 and >2.2 Ga. The detrital zircon ages from these two units and from the Battle Formation are similar to the ages of detrital zircons in the main units of the Roberts Mountains allochthon. This result is consistent with stratigraphic evidence suggesting that detritus in all three upper Paleozoic units was derived primarily from the Antler orogen. The age spectra for the three samples accordingly provide a detrital zircon reference for the ages of zircon grains accumulating along the Cordilleran margin in proximity to the Antler orogen during Carboniferous time.
|Original language||English (US)|
|Number of pages||7|
|Journal||Special Paper of the Geological Society of America|
|State||Published - Jan 1 2000|
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