ABSTRACT
Bottom sediments consist of particles of different size, shape, and chemical composition that have been transported by water, air, or ice from the sites of their origin in a terrestrial environment and have been deposited on the river, lake, or ocean floor. In addition to these particles, bottom sediments contain materials precipitated from chemical and biological processes in river, lake, and ocean waters. The relative proportions of the terrigenous and precipitated particles in sediments can vary widely. Strong biological productivity results in deposition of nearly pure calcareous and siliceous oozes on the ocean floor and in some lakes. Nearly pure terrigenous sediments accumulate on the section of the ocean floor that lies on the path of the supply of the major river and wind systems.1 Particles transported in the water become sorted and deposited according to their textural properties in different areas of the lakes and oceans. Generally, coarse material, such as sand and pebbles, settles in the nearshore zone and fine-grained particles, such as silt and clay, become deposited in deep waters with restricted currents. The particles accumulate on the bottom at different rates varying between tenths of millimeters and several centimeters per year.
