VISUALIZING PARTICLE SIZE DISTRIBUTION PROFILES IN LAKE SEDIMENTS: A STUDY OF MIDCONTINENT STORMS

Analyses and comparisons of grain size and other characteristics of sediment can be challenging, and many statistical and graphical methods fail to discern subtle changes. Standard statistical representations of data often do not accurately represent the subtle temporal fluctuations in sediment texture. Particle size distribution (PSD) of detrital sediments, as contrasted with traditional grain-size analysis, has recently come into use as a reliable and sensitive indicator of depositional environments. PSD has also been employed to identify the occurrence frequency of storm activity when a long-term record is preserved in sediment deposits of aquatic environments. In an investigation of late Quaternary paleostorm activity in the mid-continent, detailed high-resolution sampling of two sediment cores from storm-prone areas were analyzed to catalog PSD variations. One core was taken from Cheyenne Bottoms Wildlife Refuge, in central Kansas; the other was from Canton Lake, in northwest Oklahoma. Using Geosoft mapping software, we were able to more clearly visualize and quantify fine-scale changes in grain size in the two cores. By calibrating the PSD data using known storm deposits, we were able to develop a history of paleostorm occurrence. The result is a new paleostorm proxy method and a better understanding of the long-term history of stormy periods in the mid-continent.