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Practically all of the Navajo and much of the correlative Nugget Sandstone (Triassic-Jurassic) in Utah and Wyoming contain a distinctive lamination shown recently by R. E. Hunter to be diagnostic of eolian ripple translation. The Navajo has only rare tracks, bones, and
widely scattered, nondescript small deposit-feeder trace fossils. The Nugget, however, is distinguished by distinctive traces, which hold promise for environmental interpretation. Vertical and horizontal light-colored sand-filled tubes averaging about 0.7 to 1.0 cm diameter are abundant in one or more relatively thin zones in practically all exposed sections in the western Uinta Mountains and Wyoming-Idaho thrust belt. Well-preserved examples show delicate spreiten, which seem to necessitate moist, if not saturated, sand. Some Nugget traces occur in planar-bedded units that might have been subaqueously deposited, but they also occur in medium-scale to large-scale cross-bedded units with eolian lamination. The apparent restriction of this distinctive trace to the western part of the Nu get, which has been suggested to be at least partly marine, seems environmentally significant. Apparently the trace-making organism required moisture, but was capable of burrowing into dry or nearly dry (moist) dunes.
Although no modern burrowing analog can be designated confidently, the burrows of scarab beetles recognized by G. W. Hill on Padre Island are very similar. There the beetles burrow from moist interdunes into dry dunes.
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