110 L. Dudley Stanvp— 
are given in Fig. 1. One sees immediately the comparative duration 
of the cycles, the relative duration of the marine and continental 
periods in each and the approximate depth of formation of the 
deposits. By comparison of two or more graphs, using well-marked 
ys 
Cycle 
Fic. 1.—Diagrammatic representation of three cycles of sedimentation. 
M = marine deposits, showing gradation in coarseness. C = continental 
deposits. Z = zones, as determined by paleontology. The two graphs 
show the oscillations of the land surface relative to sea-level at the points 
A and B. R=position of ‘‘ravinements’’. T= junction planes 
between zones, used as time planes to show the relative time of 
commencement of each cycle at the points A and B. 
