466 PLEISTOCENE OF INDIANA AND MICHIGAN. 



most of these are rather weak and are separated by wider barren or only faintly wave-washed ver- 

 tical intervals than are those of any other group. The movement of elevation was much slower 

 during the making of the upper group of Algonquin beaches, and it was also slower during the 

 making of the Fort Brady group. It seems again to have been very much slower, if indeed it 

 did not entirely cease for a time, during the making of the original Nipissing and the Nipissing 

 two-outlet beaches. It was slow also after the time of the two-outlet Nipissing beach. 



Judgment as to the rate of recent or progressing uplift, however, depends much on the place 

 of observation. At Mackinac Island and farther south recent close-set, well-developed beaches 

 give the impression that the uplift was very slow and that the beaches had a long time to form. 

 But on the north shore of Lake Superior the beaches below the Nipissing are not well developed 

 and might be supposed to indicate that the land rose too rapidly for the making of beaches of 

 any strength. Locally, however, this is due largely to poor supply of materials. The Nipissing 

 beach itself is well developed only in recesses of the rocky shore, for the hard rocks of this 

 coast were not much affected by the waves and many stretches were bare of drift. 



It has been assumed by some that uplift has gone on in recent times at a substantially 

 uniform rate and that it is still progressing. The spasmodic movements in the past cast some 

 doubt on this assumption, although it is of course possible that both spasmodic and slow move- 

 ments took place. On the other hand, the unbroken series of rather light beach ridges between 

 the Nipissing beach and the present shore seems to show very recent and possibly still continu- 

 ing uplift in the northern part of the basins. There are some reasons, however, for believing 

 that uplift of the land is not now in progress and has not been for at least 100 or 200 years. 

 If differential uplift, like that which tilted the Nipissing beach, is now in progress it would 

 affect the north sides of the lake basins most and would die out at the hinge line. 



Indirect effects, however, would tend to extend over the area south of the hinge line, for 

 those lakes which have their outlets located north of the hinge would have their waters backed 

 up on their southern shores. If the outlets were near the hinge line the uplift would be slight 

 and the drowning effects might be negligible, but at distances of 100 to 200 miles north 

 the effects, if uplift is now in progress, ought to be perceptible in a few centuries, even if not 

 certainly measureable in 50 or 60 years. It is significant that some of the strongest evidences 

 suggesting progressing or very recent uplift have been found on the northerly shores, most 

 notably at the mouth and on the lower course of Nipigon River and of certain streams on the 

 north shore of Lake Huron. 1 These evidences seem to show very recent or progressing emer- 

 gence of the land, but, like the indirect evidences derived from the drowning of southwestern 

 shores, they give no definite time relations nor rates of uplift. It should be noted that the distri- 

 bution and character of possible recent and progressing uplifts in this region are distinctly limited, 

 for the uniformity of the tilted water plane marked by the Nipissing beach shows conclusively 

 the absence of notable warping or locally restricted uplifts; if any measurable movement has 

 occurred recently or is now in progress it must be of the character of widespread tilting, affecting 

 as a unit an extensive area north of the hinge line. 



Indirect evidence derived from features indicating recent or progressing drowning of south- 

 western shores is more ample in amount but perhaps less definite in its significance. Great 

 barrier bars and spits like Minnesota Point, at Duluth, Minn.; Chaquamegon Point, near Ash- 

 land, Wis.; Cedar Point, near Sandusky, Ohio; the point at Rondeau, Ontario; Presque Isle, at 

 Erie, Pa.; Long Point, at Port Rowan, Ontario; Burlington Beach, near Hamilton, Ontario; and 

 Toronto Island, at Toronto, Ontario, seem surely to indicate either relative permanence of water 

 level or only very slow drowning. The bars at Duluth, Sandusky, Rondeau, Erie, and Port 

 Rowan are in the area of horizontality for the later uplifts, but those near Ashland, Hamilton, 

 and Toronto are north of the hinge line but not far from it, Toronto being the farthest at a dis- 

 tance of about 60 miles. All of these places would be subjected to drowning by northern uplifts 

 affecting the outlets of the lakes in which they occur, and it is a notable fact that all of the great 

 bars mentioned are on those lakes which have northerly outlets. The outlet of Lake Erie proba- 



i Taylor, F. B., Notes on the abandoned beaches of the north coast of Lake Superior: Am. Geologist, vol. 20, 1897, pp. 120-122. 



