The use of silt grain size parameters as a paleovelocity gauge: A critical review and case study

During the past decade, several reports have been published that infer paleovelocity of deep-sea currents from grain-size parameters of fine-grained sediments. Such inferences may be a gross oversimplification. Laboratory flume experiments and theoretical treatments of suspended sediment transport indicate that particles less than 30 μm in diameter are maintained in suspension by currents of less than 4 cm/sec. Also, there are several factors that influence sediment suspension other than velocity, of which velocity may be one of the least important. It is possible that coarse silt and very fine sand analyses could provide meaningful paleovelocity information; these sediments are maintained in suspension by currents with velocities in the 1 to 15 cm/sec range. This investigation of Weddell Sea sediments provides little encouragement for this method, however.