Experiments
Major stages of the laboratory research
Two principal stages of the program dwelt upon the following two lines of research: lamination (Fig. 1) and stratification (Figs. 2, 3).
Fig. 1 : Lamination resulting
from sediment flowing into water
(1) Lamination
The following abstract of my paper (Berthault, 1986) provided the basis of my research on the deposit of heterogranular sediments in water, with and without a current :
These sedimentation experiments have been conducted in still water with a continuous supply of heterogranular material. A deposit is obtained, giving the illusion of successive beds or laminae (Fig. 1). These laminae are the result of a spontaneous periodic and continuous grading process, which takes place immediately, following the deposition of the heterogranular mixture. The thickness of the laminae appears to be independent of the sedimentation rate but increases with extreme differences in the particle size in the mixture. Where a horizontal current is involved, thin laminated layers developing laterally in the direction of the current are observed.
Video 1 : lamination (no sound)
The second series were performed at the Marseilles Institute of Fluid Mechanics.
The experiments demonstrate that in still water, continuous deposition of heterogranular sediments gives rise to laminae, which disappear progressively as the height of the fall of particles into water (and apparently their size) increases. Laminae follow the slope of the upper part of the deposit. In running water, many closely related types of lamination appear in the deposit, even superposed (Berthault, 1988).
(2) Stratification
Experiments in stratification were conducted in the Fort Collins hydraulics laboratory of the Colorado State University with professor of hydraulics and sedimentology Pierre Julien [video 2 : Fort Collins hydraulics laboratory].
Video 2 : Fort Collins hydraulics laboratory (no sound)
For these, it was necessary to operate with water in a recirculating flume traversed by a current laden with sediment. As Hjulstrom (1935) and his successors had defined the critical sedimentation rate for each particle size, the current velocity would need to be varied. By modulating the current velocity, a superposition of segregated particles could be obtained.
The flume experiment showed that in the presence of a variable current, stratified superposed beds prograde simultaneously in the direction of the current (Fig. 2) [video 3 ].
Video 3 (no sound)
The result, on the scale of strata, is also conform, on the scale of facies [video 4 ] to Golovkinskii, Inostranzev and Walther’s law (Walther, 1894 ; Middleton, 1973; Romanovskii, 1988), according to which the extension of facies of the same sequence is the same both laterally and vertically [video 5 ].
Video 4 (no sound)
Video 5 (no sound)
Fig. 2. Typical longitudinal view of deposition (flow from right to left).