--> Abstract: Geometric Trends for Floodplain Lakes in High Accommodation Floodplains, by Scott Stoner and John Holbrook; #90078 (2008)

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Geometric Trends for Floodplain Lakes in High Accommodation Floodplains

Scott Stoner and John Holbrook
Geosciences, UTA, Arlington, TX

Fluvial systems are prolific hydrocarbon reservoirs. Accordingly numerous studies have addressed architectural styles and aspect ratios aimed at the “net” channel-belt reservoirs. Floodplain lake deposits are known to typically constitute the majority of the “gross” sections of fluvial systems in high-accommodation settings. Virtually no comparable studies have been done to quantify lake geometry and evolution. Partly this reflects the few examples of high-aggradational fluvial systems in the modern. We made a first attempt to measure trends in floodplain lakes by examining four lake-rich fluvial sites where lakes were in early developmental stages. These included two systems located on the Mexican Gulf Coast, one deltaic system in Alaska, and one interior fluvial section in Columbia. We defined lakes as forming on the floodplains next to and between channel belt levees. Sediment fill is mainly delivered here by smaller secondary channels that feed crevasse splay deltas and deliver plumes of mud. For each lake we measured length, width and areas using satellite images obtained from Google Earth.

The lakes in the study areas ranged from fractions of a kilometer width to over one hundred kilometers, with shape and area of the lakes being highly variable . Much of the variability stemmed from the tendency of large lakes to undergo partitioning into multiple smaller lakes as they became dissected by avulsive small channels during filling creating complex relationships between lakes, small feeder channels and splay deltas. Consequently the relationship between trunk channel/channel belt size and lake size was weak. Channel belt density however appears to be the primary controlling factor in lake size. The lakes maximum size is limited by the distance between the channel belts or the distance between a channel belt and floodplain termination.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas