. Bulletin of the Geological Society of America. Geology. THEORY OF FORMATION OF DELTA CUSPS. 419 side current lines in figure 12. A rounded delta may thus become a cus- pate one. If the ratio between river and sea increases in favor of along- shore action a cuspate delta may be changed to a rounded one. Included marsh areas are drawn in this type because where a dominant movement alongshore is indicated on the maps such areas usually occur. They do not neces- sarily result from this hypothesis of growth, and may occur in any delta where the ad- vance been by leaps. The third method of fo
. Bulletin of the Geological Society of America. Geology. THEORY OF FORMATION OF DELTA CUSPS. 419 side current lines in figure 12. A rounded delta may thus become a cus- pate one. If the ratio between river and sea increases in favor of along- shore action a cuspate delta may be changed to a rounded one. Included marsh areas are drawn in this type because where a dominant movement alongshore is indicated on the maps such areas usually occur. They do not neces- sarily result from this hypothesis of growth, and may occur in any delta where the ad- vance been by leaps. The third method of formation is where two currents move alongshore, one from the right and the other from the left, toward the mouth of the stream. The river may act in this case as the projection of the land at the beginning of a new cycle was sup- posed to do in starting the growth of a current cuspate foreland (page 403). The three methods Growth of growth can doubt- Current. less be easily distinguished upon the ground. It is not so easy upon the maps, for the main indica- tion as to current upon the delta foreland is the deflection of small streams. Such streams often do not exist. Offsets and overlaps are not com- mon upon delta forelands. If there is a dominant current along a coast a delta occurring upon it may with great probability be referred to the second method of growth. Like so many other things in this world, this is wholly a question of ratios, and in any given delta there will be some on and off shore action and some alongshore Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Geological Society of America. [New York : The Society]
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