POSTGLACIAL DEVELOPMENT OF CONNECTING EIVEES OF GREAT LAKES. 487 



on the west side of Baby Creek and in the western part of Delray. Other duny sand ridges 

 along Rouge River in Springwells Township may have had a different origin, but all the gravels 

 and sands in the southwest part of the city and in Woodrnere and Delray were evidently deposited 

 when the river first broke through the moraine. (See fig. 13.) 



The cutting through the moraine at that time was evidently not very deep, and the low 

 ground along Rouge River southwest of the city was occupied by a shallow lake or expansion of 

 the river which may be called Lake Rouge. In this lake the gravel and sand derived from the 

 cutting of the distributaries and the main channel were deposited as a scattered thin delta. 

 That this is really the explanation of these gravel and sand deposits seems clear from their rela- 

 tion to the river. • The main channel at that time must have been the same as at present, but was 

 not so deep. It was probably not excavated much below the present surface of the river, and 

 south westward toward the fort, where the river entered Lake Rouge, it was probably not exca- 

 vating at all, but spreading out widely and depositing gravel and sand. The gravels at the fort 

 stand precisely in line with the cut of the main channel through the moraine and exactly where 

 the spreading, slackening current would drop its load on emerging from the narrow cut. A 

 considerable part of this gravel deposit, the eastern part of the bar especially, has probably been 

 cut away by the modern river. One or two gravel bars were made at the same time on the 

 Canadian side, the largest being on the north part of Fighting Island. The relations of all these 

 features taken together present a very clear record of the river's first cutting through the 

 moraine. 



Lake Rouge covered the south half of Springwells Township and nearly all of Ecorse Town- 

 ship, reaching down'to the head of Grosse Isle. It was 10 or 12 miles long from north to south 

 and at least 6 or 7 miles wide, but its precise limits on the Canadian side have not yet been 

 determined. So small a body of water could hardly be expected to develop perceptible shore 

 lines, but Lake Rouge did develop a faint but well-defined one on its west side and on the north 

 end of Grosse Isle. From the rear fight of the Grosse Isle north channel range fights a faint ridge 

 of gravel runs south for a couple of miles just west of the beach road. Most of the cottages are 

 budt upon it. Its altitude at the north end of Grosse Isle is about 13 feet above the water, or 

 about 588 feet above sea level. This is about 7 feet below the first St. Clair beach in the basin 

 of Lake St. Clair. • This beach of Lake Rouge, or the first Rouge beach, as it may be called, is 

 also a correlative of the upper Algonquin beach and marks another step in the descent from 

 Early Lake Algonquin to the Lake Erie basin. 



DETROIT RIVER NEAR TRENTON AND AMHERSTBTTRG. 



The finest development of abandoned distributaries is in the vicinity of Trenton and 

 Amherstburg. The new river here found obstructing its flow a broad, flat-topped ridge which 

 was composed in part of ordinary till like the ridges already described, in part of a bowlder 

 bed set in very tough till, but in part of limestone in massive beds. As at St. Clair, the crest 

 of the ridge appears to have extended northwest and southeast, so that, when the river first 

 flowed over it, most of the distributaries tended to flow southwest. Plate XXXI shows the 

 distributaries in the vicinity of Trenton and Amherstburg. 



The distributaries of this locality are extremely complex. Tfiere are early ones and later 

 ones and others that the river has scarcely left dry. Indeed, the river still occupies a considerable 

 number, though most of those now occupied are merely fragments. There are also a number 

 of distributaries that are now drowned and are seen only in the bed of the river or on the floor 

 of its estuary. 



