![]() ![]() ![]() Geological Survey, Denver, CO (United States). ![]() Stacked sets of remnant dunes separated by erosional surfaces illustrate the control of sand deposition on eolian sabkhas by the local water table. This topography is commonly filled in with ripple strata that form as dry sand again blows across more ยป the sabkha. The avalanche strata, being slightly coarser grained, are preferentially deflated, leaving microtopography. Typically, ripple strata of the dune apron and the toes of avalanche strata are preserved in dune remnants. The remnant sets form when dunes migrating across a sabkha are partially wetted as the water table rises slightly (on a scale of tens of centimeters) the lower part of the dune with wetted sand remains on the sabkha as the rest of the dune continues to migrate. Thin, remnant eolian dune sets are common in Nugget sabkha sandstones. The types of sedimentary structures and erosional features in Nugget sabkha sandstones indicate a close relationship between sand deposition and erosion and fluctuations in the local water table. Structures in Nugget sabkha sandstones are predominantly wavy or irregular bedding and thin, remnant sets of dune cross-strata consisting of eolian ripple and avalanche strata. The Jurassic Nugget Sandstone in the Vernal, Utah, area is characterized by thick (up to 25 m) sets of cross-stratified eolian dune sandstone separated by either erosional planar bounding surfaces or thin (mostly < 3 m) sandstones interpreted as sabkha sandstones. ![]()
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