FLUVIAL – EOLIAN INTERACTION IN MODERN CONTINENTAL SEDIMENTARY BASINS

We evaluate the interaction between fluvial and eolian systems in several continental sedimentary basins from satellite imagery. We aim to assess conditions that may have existed in the past to produce mixed successions of eolian and fluvial rocks (e.g., Cutler and Chinle Groups, Utah, Leman Sandstone, North Sea). We focus on aggradational fluvial systems in sedimentary basins because only these will be preserved in the rock record. We observe three general fluvial-eolian interactions: 1) termination of distributive fluvial systems (DFS) in an eolian dune field, 2) rivers on DFS that cross eolian dune fields, and 3) rivers that lie in an axial position adjacent to dune fields. In the Tarim Basin, China, rivers enter the sedimentary basin and form DFS that primarily terminate in a large dune field. The gradient on the DFS appears to be controlled by upstream input of sediment and discharge. As the river system enters the dune field, additional sediment is available for transport however the river can not increase its gradient to accommodate transport of this sediment load. Ultimately the river system splays into several smaller, interdune channels that eventually disappear into the dune field (either through evaporation or infiltration). Some of these terminations form lakes that are surrounded by dunes. This arrangement forms the most common fluvial-eolian interaction, with similar terminations observed in several other sedimentary basins (e.g, basins around the Gobi, Sahara, and the Karakum Deserts). Rarely, larger rivers can cross the dune fields in a sedimentary basin. For example, the Hotan River crosses the Tarim Basin along an approximately 400km long transect, forming a large DFS that is mostly covered by dunes. This braided river decreases in size downstream and is confined between dunes as it crosses the desert. Finally, rivers may run parallel to the dune field along the edge of the sedimentary basin, with an apparent interplay between encroaching dunes and eroding river. Sharp boundaries between the erg and the river system are observed along these locations, with vegetation commonly populating the active floodplain area. Wet interdunes are common along and downfan from all of these fluvial-eolian interaction areas. These distributions most-likely best represent configurations that formed the rock record.