812 Goldthwait — Twenty-Foot Zbrrdce arid 



coastal movements to successive portions of the stone age, cop- 

 per age, ami bronze age lias been worked out, and the 

 approximate date of csfch shoreline has been estimated.* A 

 brief outline of the conclusions reached by Broegger and others 

 who have been investigating the post-glacial movements in 

 Scandinavia will serve as an interesting commentary on the 

 hypothesis of subsidence of the Canadian coast during the 

 Micmac stage. 



At the close of the last glacial epoch, the Scandinavian coast 

 stood several hundred feet lower than it does now; This time 

 of maximum submergence has been called the " Kristiania 

 period " by Broegger. An open sound then extended across 

 the peninsula, connecting the Skager Rack with the Gulf of 

 Bothnia. The shoreline of this earliest marine stage now 

 stands about 700 feet above the sea at Christiania. The Yoldia 

 clay, characterized by boreal forms like those in the Cham- 

 plain clays, mark the deposits of the Christiania period. Broeg- 

 ger has shown that the ice sheet had not entirely withdrawn 

 from the estuaries at the time of the greatest submergence, 

 for the Yoldia clays extend up the estuaries only as far as the 

 great terminal moraine. Judging, therefore, from the absence 

 of Yoldia clays behind this moraine, the emergence of the 

 Scandinavian coast began before the heads of the estuaries 

 were abandoned by the ice. In Canada, it will be remem- 

 bered, a similar early emergence of the newly uncovered coast 

 from the sea has been inferred from a different kind of evi- 

 dence, — namely, the weak character of the highest beach. 

 Above the Yoldia clays, other marine clays, known respec- 

 tively as the Area, the Mytilus, and the Cardium clays, show 

 a gradual retreat of the Arctic fauna and the advent of more 

 southern forms. The climax of this emergence of the coast 

 was marked by the existence of a great fresh-water sea in the 

 Baltic basin, with a fauna characterized by lacustrine spe- 

 cies of such genera as Planorbis, Limncea, and Ancylus. 

 This Ancykcs group of sands and clays is found at many places 

 around the Baltic, up to altitudes of more than 100 feet above 

 the sea. Broegger appears to regard this Ancylus sea as 

 impounded not by an emergence of the straits to a higher level 

 than the present, but rather to a blockading of the straits by 

 an ice lobe. The time occupied by this first post-glacial emerg- 

 ence has been estimated by Broegger to be about 9000 years.f 



* W. C. Broegger : Strandliniens beliggenhed under Stenalderen i det 

 sudoestlige Norge. Norwegian Geological Survey, No. 41, pp. 339, 1905. 

 (Review by G C. MacCurdy) Science, vol. xxiii, pp. 778-780, 1906. 



f Gerard De Geer : On pleistocene changes of level in eastern North 

 America. Proc. Boston Soc. Nat. Hist., vol. xxv, pp. 460-461. A. Geikie: 

 Text book of geology, 4th edition, London, 1903, p. 1333. W. C. Broegger, 

 op. cit., p. 283. 



