A bed of sediment or sedimentary rock that was deposited from a turbidity current. A turbidity current is an underwater flow produced by movement of a turbid mass of water downslope as a result of the excess weight of the turbid water as compared with the surrounding clear water. Turbidity currents are therefore a type of gravity (or density) current; such currents are kept in motion by gravity acting on relatively small differences in density between different fluids (gases or liquids) or between different parts of the same fluid mass. In some gravity currents the density difference results from a difference in temperature or salinity (for example, fresh water flowing above salt water), but in turbidity currents it results from the presence of dispersed sediment.