Problems, Middle Mississippi River Region, Pleistocene Time 179 
to time, it was felt that this was a more desirable method. The 
center of the trough of the Mississippi at the southern edge of 
the St. Louis, Missouri-Ilinois quadrangle, about opposite 
Jefferson Barracks, was used as the point of reference, all dis- 
tances being computed from this point. 
THE FESTUS TERRACE 
Near the mouth of Plattin Creek, and for several miles up 
this creek, fragments of a terrace may be observed. Large areas 
of the flat top of the terrace may be seen in the vicinity of Fes- 
tus and Crystal City, Missouri. The elevation of the flat top of 
the terrace is 445 feet near the mouth of the creek, but 
this decreases with increasing distance from the Mississippi 
River. The terrace has completely disappeared upstream 
before the place where the 440-foot contour crosses the creek. 
Apparently the upper surface of the terrace displayed in 
this creek is not parallel to the gradient of the stream, nor is it 
horizontal; but it has a very slight slope contrary to the direction 
of the stream. The greatest elevation of the flood plain of the 
Mississippi is not quite 400 feet in this vicinity. The mean datum 
Plane of the Mississippi is 375 feet opposite the mouth of Plattin 
Creek. The top of the terrace is, therefore, about 50 feet above 
the flood plain and 70 feet above the mean datum plane of the 
river, 
A cut immediately west of the First Baptist Church in Festus 
shows the stratified nature of the terrace (Fig. 4). The terrace 
consists of alternating layers of silt and fine sand with a few 
thin beds of fine gravel. None of the layers exceeds a foot 
in thickness and they are usually thinner. The absence of coarse 
sand in the terrace at this locality is significant, since the coarse- 
grained St. Peter sandstone forms conspicious and numerous 
outcrops nearby. It would appear that this nearby sandstone 
did not furnish much of the substance of the terrace. 
Terraces similar to the one on Plattin Creek can be found 
in every stream of considerable size between St. Louis and 
