Paper No. 11
Presentation Time: 11:45 AM
THE WHISTLING AND CHIRPING BEACH SANDS OF BARBADOS
Most modern beaches in Barbados have carbonate sands except for those facing the Atlantic coastline, which has mixed carbonate-siliciclastic and purely siliciclastic sand beaches. Some parts of the latter consist of a type of sediment that emits a chirping or whistling sound when kicked or walked on. Sands from two beaches with this property were collected and analyzed to determine the cause of this phenomenon. The grains were sorted by size and the shape was analyzed using a stereographic microscope. The sands were found to be composed of about 70% quartz, about 25% skeletal fragments, and 5% opaques. Grain sizes vary from about 1.0 mm to 0.125 mm. The chirping property is related to grain shape and size distribution. Similarly sized grains create planar interfaces at contact surfaces because most grains are flat and/or angular. Rod shaped grains (second in abundance) roll over the top of the planar surfaces created by the angular clasts when a directional force is applied. The audible chirping noise most probably is caused when the rod-shaped grains roll over the planar surfaces, thus squeezeing out the air trapped between the grains.