364 PLEISTOCENE OF INDIANA AND MICHIGAN. 



From here the beaches run in an almost direct line northeastward past Clio, Arbela, Millington, 

 and Juniata, nearly to Cass City. Northeast of Flushing the third beach ridge of this series be- 

 gins to appear below the others and from Clio northeastward three beaches become more and 

 more distinct. Northeast of Juniata three ridges pass out upon a plain of increasing flatness 

 and are deployed at wider intervals which increases their distinctness as individuals. In this 

 part of their course they are generally composed of gravel, but are in many places covered over 

 with fine sand which has blown in across the region from the west. Two or three miles from 

 Cass City the beaches are buried, partly in sand but mainly in a gravelly plain, probably in large 

 part a delta deposit made at the time of Lake Whittlesey. 



From the reentrant angle north of Ubly the main moraine of the Port Huron morainic 

 system, made up of three or four rather irregular subsidiary ridges, runs southwest to Vassar, 

 its complexity gradually disappearing as its western or later parts became water-laid. At 

 Vassar it turns gradually west, passes along the north side of Cass River through Saginaw and 

 on northwestward to a point east of Midland, where it turns gradually north and in north- 

 western Bay County curves gradually back to the northeast. It was on this moraine that the 

 ice front rested during the time of Lake Whittlesey, when the lake waters east of the "thumb" 

 were raised to the Whittlesey beach and the Arkona beaches were drowned. The Arkona 

 beaches in the Saginaw basin were largely made before the building of this moraine, and it is a 

 notable fact that where they run northeast from Millington toward Cass City the ridges appear 

 to keep their full strength until they are lost in the sand, in spite of the fact that in the last 

 25 miles they extend up the east side of a rather narrow valley with the main moraine of the 

 Port Huron system forming a great barrier facing them on the west. It is evident on the 

 least reflection that the strong beaches near Cass City could not have been made by wave action 

 at the head of so long and narrow a valley, and hence could not have been made after the main 

 moraine of the Port Huron system was built. The evidence indicates very clearly that the 

 beaches there were made by heavy seas coming from the northwest and passing with full force 

 over the place where the Port Huron system now stands as a range of hills 20 to 60 feet higher 

 than the beaches. Further, although the western slope of the Port Huron system at the level 

 of this beach would have been exposed, if present, to a wide expanse of water, it shows no sign 

 of a beach nor any effects of wave action. It seems entirely clear, therefore, that the Arkona 

 beaches in the Saginaw basin were made before the building of the main moraine of the Port 

 Huron system. The relations seem conclusive in the region southwest of Cass City, and the 

 same phenomena are repeated in three other localities. 



On the northwest side of Saginaw Bay, where the Arkona beaches would naturally be 

 expected to come into similar relations with the Port Huron system, the ground is so flat and 

 is so extensively covered with sandy outwash and delta deposits that the beaches, which were 

 probably weak on account of the flatness of the region, are buried and lost long before they reach 

 the front of the Port Huron system. On this account no similarly significant relation of the 

 beaches to the moraine was observed on the west side of the Saginaw basin. 



OVERBIDDEN BEACHES ON THE "THUMB." 



From a point 2 or 3 miles south of Cass City around the " thumb" to the vicinity of Applegate 

 and Croswell the Arkona beaches were entirely overridden and destroyed by the advance of 

 the ice at the time of the building of the Port Huron system. In all probabihty the beaches 

 were formed in full strength continuously around the "thumb," passing some distance north of 

 Ubly, but all that part is completely buried under the massive deposit of the morainic system. 

 That this was the case seems clearly estabhshed by the fact that south of Applegate and Cros- 

 well the Arkona beaches reappear three in number and in full strength and at the same level 

 as in the district southwest of Cass City, when measured along the fine of the isobases. The 

 inference as to their strength in the overridden interval is not based on the strength of these 

 beaches in the Saginaw basin, where they stand for the duration of Lake Saginaw in addition 

 to that of Lake Arkona, but on their strength in the Black River valley, where they represent 

 only the duration of Lake Arkona and were under construction for the same length of time 

 as those in the overridden district. 



