Oblique dunes have orientations that are intermediate between those of transverse and longitudinal dunes. The oblique dunes studied are reversing dunes which undergo no net annual migration when associated with normal meteorological patterns. From April 1980 through September 1980, the dunes migrated up
to 65 feet (19.8 m) northwestward under the influence of prevailing onshore winds. High velocity northerly winds (November 1980 through
February 1981), associated with the passage of winter frontal systems,
caused the dunes to rapidly migrate 65 feet (19.8 m) southward. Volumes
of sand transported by these strong winds were commonly reduced by accompanying rainfall. In October 1980 and March 1981 neither wind direction was dominant, and frequent changes in wind direction caused many of the dunes to become flattened. Hurricanes, which strike the
area in late summer, have had no lasting effects on the dunes. Three major stratification types were observed in trenches and
on etched surfaces. Translatent strata were deposited by wind ripples;
grainfall deposits accumulated when saltating grains settled on leeward
slopes of the dunes, and grainflow cross-strata were developed by avalanching on leeward slopes. Preservation of these stratification
types occurred in zones of net deposition, predominantly leeward of the
dune crests. Strata deposited during the summer wind regime dip northeast,
whereas the winter strata dip in a southerly direction. The winter deposits
are best preserved in the central cores of the dunes. This suggests
that either the high velocity winds of the initial winter frontal
systems destroy large volumes of the summer deposits, or that the dunes migrate southward, under the influence of dry northerly winds, during
droughts. Oblique dune deposits should be difficult to discern in the
rock record, because they may contain aspects of either transverse or
longitudinal dunes. It is likely that some ancient oblique dunes have
been mistakenly described as other dune types in the literature. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/6778 |
| Date | 11 December 2009 |
| Creators | Weiner, Stephen Paul |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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