Sand and gravel from shallow seas

Abstract

Various factors which influence the economic feasibility of offshore mining are discussed. The mined sands and gravels are used for constructional purposes. Therefore, some specifications of the grainsize distribution of the exploitable product are mentioned. A gravel exploration by the Netherlands Geological Survey in an area off the Norfolk coast is mentioned. Some special samplers, used for this purpose, are described. Sand and gravel on the shelves have been transported and supplied by rivers, glaciers, wind and locally by longshore currents. Marine erosion may contribute as well. The North Sea and English Channel are good examples of an aggregate-bearing shelf, since shells, sands and gravels are all present. The availability is at least as important as the transporting agents. Controlling include a.o. climate, tectonic instability and distance from the source area. Even in the Pleistocene the weathering processes in the tropical zones resulted in only small amounts of sand and gravel reaching the present-day shelf areas. In the subtropical zone the humidity and tectonic instability are a prerequisite for their presence) whereas in the temperate zones various mechanisms have led to mineable deposits. From a combination of prospective areas and densely populated regions it follows that only very restricted parts of the shelf are of interest as far as mining is concerned.