SUPERFICIAL GEOLOGY OF DUNDAS VALLEY. 117 



The well did not pierce the Trenton to its base. Below the 

 Trenton we have the Potsdam and Sienite,and above the mouth of 

 the well the Clinton and Niagara Groups. This section is drawn 

 from N. E. to S. W. The beds dip at about 30 feet to the mile. 

 The Medina Group runs out at Oakville. The strike of this group 

 being in an E. and W. direction, it appears, in the section of the 

 Eastern Escarpment from Niagara to Ancaster, on the same horizon, 

 or 120 feet above the level of the lake. From this section the Med- 

 ina Group appears to be only 367 feet thick at Dundas, 120 feet of 

 which is above the lake level thus leaving 247 feet under that level. 

 The clay beds in the same neighborhood have, however, been pierced 

 to a depth of 60 feet below the level of Lake Ontario, thus showing 

 the absense of the Medina Group to that depth.|| 



On the Sydenham road, on the 16th and 17 th lots of the first 

 range of Flamboro' West, the Clinton Group is 100 feet 11 inches 

 thick. This is overlaid by 127 feet thickness of beds of the Niagara 

 Group.f 



The rocks of the section in the neighborhood of Dundas, form 

 two separate and distinct terraces. The lower and more marked 

 escarpment presents the strata beneath the band of chert and lime 

 stone, which caps the precipice at Flamboro' West. 



The upper escarpment, composed of the dark colored bitumin- 

 ous and magnesian limestones, and their accompanying beds, rise 

 more gradually in a succession of steps, terminating at the summit 

 in a wide extent of Table land. 



The elevation of the top of the escarpment at Dundas, is 520 

 feet above lake level. 



OLD BEACHES. 



Dr. Robert Chambers, in his Ancient Sea Margins, in speaking 

 of the region of the great American Lakes, says : " This district 

 presents some memorials of ancient sea levels which are not, perhaps, 

 exceeded in interest in any part of the globe. To the north of the 

 lowest lake, Ontario, which is 232 feet above the ocean level, the 

 gentle slope, composed of a deep bed of clay enclosing scratched 

 boulders, is traversed lengthways by a series of ridges, nine in num- 

 ber, at a rising series of levels." 



II Geology of Canada, page 903. 

 tGeology of Canada, page 326. 



