Surface tension phenomena in the magnetization of sediments

Summary. This paper examines the role of surface tension effects in the post- depositional magnetization of a sediment. After deposition, magnetic grains experience both frictipnal and magnetic forces but during dessication surface tension forces also become important. It is shown from order of magnitude calculations that surface tension forces will predominate for grains smaller than about 1.3 mm and therefore remanence changes may occur in fine grained sediments upon drying. A simple model predicts that in a moist sediment containing bladed magnetic particles the effect of vertical fluctuations in the level of saturation will be to shallow the remanent inclina- tion. Remanence changes due to surface tension are demonstrated in a controlled experiment with synthetic sediment. Implications for sediment palaeomagnetism are discussed and alternative drying procedures for sedi- ments are suggested.