Abstract

The Lynndyl Dunes lie just west of Lynndyl and north of Delta, Utah. Having a total area of about 575 sq km (220 sq mi), it is one of the largest dune fields in Utah. The Lynndyl Dunes occupy the northwestern portion of the relict Late Pleistocene Sevier River Delta, which was built during the Provo stage of Lake Bonneville. Deltaic and associated beach-ridge sediments constitute the principal source of sand for the Lynndyl Dunes. Eolian sand is deflated especially from the delta-front region, and is transported downwind (northeast) as migrating dunes by the resultant southwesterly winds.

A geomorphic map of the study area shows (1) the extent of the dune field, (2) active, semi-active, and stable dune areas, and (3) subareas of active and stable dunes, distinguished on the basis of eolian form. The spatial distribution of dune forms within the active region displays a generalized upwind to downwind sequence of parabolic dunes, barchans, climbing and falling dunes, and akle. This represents a progression from dune types requiring a moderate sand supply to a type adjusted to a large sand supply. An increase in net sand accumulation occurs with distance from the primary sand source because of (1) a gradual downwind increase in elevation, and (2) the presence of the Sand Hills, a bedrock obstacle oriented transverse to the resultant southwesterly wind. Stabilized dunes tend to occur in dune-field margin locations, and are divided into sharp, intermediate, and muted form subareas.