Transport of Sediments by Waves, Adriatic Coastal Shelf, Italy

Abstract

Knowledge of marine-sediment transport in shallow water is as yet insufficient to give much help to the geologist who maps the distribution of ancient sandstone bodies. In order to improve this knowledge, the bottom sediments of the Adriatic Sea near the Italian coast were sampled and analyzed. These sediments were transported as uniform suspensions. A close relation was found between certain grain-size parameters, particularly the 1 percentile, and sea depth, indicating that turbulence induced by waves was a major factor in the sand distribution. Another important factor that generally has been overlooked is percentage of sand in the sediment source for the area. If these source sediments contain little sand and consist almost entirely of silt and clay, the sand remains close to shore. If, however, sand is the predominant constituent of the source sediments, as commonly occurred in ancient seas, sand probably can be spread by waves across extensive areas as deep as wave base. The grain size of the sand also is an important factor in its distribution, some sand suspensions being displaced by gravity and some not. Therefore, grain size may determine the transport mechanism and, thus, the sediment distribution. An understanding of these factors by the petroleum geologist is essential in his mapping and projection of sandstone deposits in the subsurface.