Dating the upper Cenozoic sediments in Fisher Valley, southeastern Utah (USA)

More than 140 m of upper Cenozoic basin-fill sediments were deposited and then deformed in Fisher Valley between about 2.5 and 0.25 m.y. ago, in response to uplift of the adjacent Onion Creek salt diapir. In addition to these basin-fill sediments, minor amounts of eolian and fluvial sand were deposited in Holocene time. The sediments, whose relative ages are known from the stratigraphy, are predominantly sandy, second-cycle red beds derived from nearby Mesozoic rocks; most were deposited in a vertical sequence, filling a sedimentary basin now exposed by fluvial dissection. We have applied a variety of established and experimental dating methods to the sediments in Fisher Valley to establish their age and to provide time control for the recent history of the Onion Creek salt diapir.