Abstract |
Sediments now accumulating in St. Louis Bay are detrital silicates with trace amounts of particulate organic matter and shell fragments. Twenty seven percent of the Bay surface sediments are sands, the remainder being sandy silt-clay mixtures. Average grainsize composition, by weight, for 62 Bay sediments is a trace of gravel, 34 percent sand, 30 percent silt and 36 percent clay. Sand is supplied by westward longshore drift from the man-made north shore beach of Mississippi Sound. There may be two sources of sand as evidenced by the common occurrence of angular and well-rounded quartz grains in the same size class. Sand accumulates near the Bay mouth, in places only inches thick, overlying the continental Citronelle Formation. Silt and clay are supplied by the Wolf and Jourdan Rivers and on the flood tide from Mississippi Sound. Salinity of the Bay water, 7 to 8 percent, is sufficient to cause mud flocculation. (Author) |