Abstract

Nineteen sand waves, considered antidunes, are exposed on a bedding plane of Mount Toby Conglomerate near Sunderland. They are nearly symmetrical, with smoothly rounded crests somewhat sharper than the intervening troughs; slip faces are not developed. Average wave length is 63.3 cm, average height 6.5 cm. Cross laminae within waves are parallel to upstream wave fronts, indicating that the antidunes were migrating upstream. Current direction is known independently from cobble imbrication in adjacent beds, regional grain size trends, oriented structures, and known source areas. The antidunes formed in water about 1.6 cm deep, flowing at 100 cm/sec down a paleoslope of at least 2.7 degrees , compatible with sheetwash on the surface of an alluvial fan. Upstream-dipping cross laminae are not limited to the unit displaying sand waves, but occur abundantly in many other beds.

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