Eolian and adjacent deposits of Great Sand Dunes, Colorado form a small but sedimentologically complex deposit. Eolian sediments can be subdivided into three provinces trending downwind (northeast): I) low, (as much as 10 m high) alkali-cemented dunes forming discontinuous rings around broad, flat-bottomed, ephemeral lakes; II) undulating, vegetated dunes as high as 10 m, of barchan, parabolic shrub-coppice, and transverse type, with varying interdune types; III) high (as much as 200 m) transverse dunes with little or no vegetation and no true interdune deposits. Eolian deposits are in contact with, or intercalated with, fluvial, lacustrine, and alluvial-fan deposits and lap onto crystalline basement rocks of the Sangre de Cristo Range.
Analysis of a 40-year span of aerial photographs and field observation of sand transport and cross-bedding dip directions indicate that the main dune mass (province III) is accreting vertically and that dune types are growing in complexity, in particular the star dunes. This change from lateral migration to vertical growth most probably reflects Holocene changes in wind regime.
The Great Sand Dunes are an example of a localized, cool-climate, intermontane eolian deposit, characterized by extensive fluvial reworking. With its rapid variation in thicknesses, sedimentary structures, and associated sedimentary deposits, such a deposit would be difficult to interpret accurately in the ancient rock record. However, such a deposit could be of economic importance in petroleum and uranium exploration, and in aquifer evaluation.
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This volume is a collection of papers that resulted from a symposium on Recent and Ancient Nonmarine Depositional Environments which was held in Casper, Wyoming on June 3 to 7, 1979. The nineteen papers may be divided into: (1) a review of recent and ancient nonmarine modes, (2) alluvial fan and fluvial deposits, (3) lacustrine deposits, (4) eolian deposits. Knowledge of the physical, biological and chemical characteristics and depostional environments on nonmarine sedimentary deposits has increased significantly over the last decade. Correspondingly, there has also been an increase in our ability to apply this knowledge to the exploration and exploitation of contained energy resources and minerals.