ARTIFICIAL DKKORMATION OF SOFT 13EDS 



329 



of the charcoal band occuiTed in the first stage of the experiment. Later 

 stages show coincident development in different parts of the section of 

 doming and npthrnst faulting accompanied by extensive flowage of the 

 subsurface strata. 



This experiment duplicates, it is believed, on a small scale the phe- 

 nomena of the mud lumps'"^ which rise in the delta of the Mississippi 

 River a few feet above water level. A river delta affords a particularly 

 favorable field for such phenomena because of the constant interplay of. 

 marine and river currents and the resulting continuous shifting of the 



■^^^llii^ 



Figure .5. — Another View of the water-laid Beds shown in Figure 1, 



This result is obtained after adding sand and shot to the surface load and subjecting 

 the sand cover in the left third of the section to current scour. The thinning of the 

 sand cover, combined with the increased load, developed the upthrust clay plug seen on 

 the left side of the figure. 



areal relations of heavy, coarse sediment and those of lighter and more 

 mobile character. While the mud lumps of the Mississippi appear to be 

 unique in rising above the surface of the water, probably through being 

 composed of material sufficiently tenacious to withstand current and 

 wave action for some time, similar phenomena doubtless occur in many 

 other deltas which do not become apparent through failure of the up- 

 squeezed masses to reach the surface of the water. These experiments 



= G. D. Harris: Geo). Surv. of TiOuisiana, Kept, for 1899, pp. 119-121; Rept. for 1902, 

 pp. 38-39. 



E. W. Shaw : TJ. S. Geol. Surv. Prof. Paper no. 85B, 1913, pp. 11-27. 



