Description Load cast

wartlike load casts in hettangian arkoses northern aquitaine basin

load casts form on underside of overlying denser layer (sands, coarse sands, or gravels), superimposed on less-dense hydroplastic layer (muds, silts or finer sands). casts take on form of slight bulges, swellings, deep or rounded sacks, knobby excrescences or highly irregular protuberances. in profile, appear row of flattened, lobe-shaped masses of similar size, shape, , spacing bulging lower layer. between lobes penetrate flame-like fingers or diapir-like shapes underlying less-dense layer. in 3-d, lobes reveal equant elongated pillow shapes separated each other narrow clefts. in profile, succession of lobes , fingers can modelled row of semi-circular lobes touching each other @ finger tips; characteristic wavelength l can consequently attributed lobes. according contrast in density , viscosity of specific layers, wavelength produced instability varies considerably values between few millimeters , 10 centimeters. extreme examples have been reported wavelengths 10 meters.

normally lobes/pockets , fingers/diapirs relatively symmetrical vertical, can become asymmetrical in places. lean consistent direction, interpreted direction of paleocurrent. asymmetrical load casts called squamiform or flow casts. important note in load casts flame-like fingers never pierce upper layer, whereas in flame structures do.