Nr. 6] KVARTÆR-STUDIER I TRONDHJEMSFELTET 7 



kede bassiner i den gamle dalbund er et karakteristisk fælles- 

 træk for dem begge. 



Vi bliver her nødt til at se fænomeiiet paa samme maate 

 som de amerikanske geologer allerede for længe siden har fundet 

 forholdet at være saavel paa Amerikas østkyst som paa vest- 

 kysten: »The submarine continuations of the channels of the 

 St. Lawrence, Hudson, Deleware, Susquehanna, and Mississippi 

 rivers are cited as proof that the Atlantic coast of North America 

 was uplifted during the Pliocene period, attaining, probably in 

 the early part of the Quarternary, an altitude of 2,000 to 3,000 

 feet above its present hight. Its northern coasts were also up- 

 lifted, as shown by fiords. The elevation of British Columbia, 

 according to Dr. G. M. Dawson, was at least 900 feet. That it 

 may have greatly exceeded this amount, is indicated by the 

 submerged channels discovered on the coast of California bj' 

 Prof. George Davidson of the U. S. Coast Survey. Not less than 

 twenty of these sunken fiords have been found between Cape 

 Mendocino and San Diego, within a distance of about 700 miles, 

 some of them reaching depths of 2,000 to 2,500 feet. Like the 

 Hudson submarine channel and fiord, these have all the distinc- 

 tive features of subaerial erosion, and they are regarded by Prof. 

 Le Conte as decisive evidence that this part of the continental 

 plateau has been greatlj^ uplifted, similarly with its eastern 

 portion and probably at the same time. The submarine channels 

 of California, however, are not continuations of the present rivers, 

 and none exist opposite to San Francisco and the Golden Gate. 

 Prof. Le Conte therefore suggests that the drainage of the great 

 valley of California during Pliocene time probably passed into 

 the sea farther south by a deeply submerged channel which is 

 traced bv soundings in the Monterey Bav« (The American Geo- 

 logist. Vol. Vni (1891), pag. 54). 



Efter dybdeforholdene at dømme synes det meget sandsynlig 

 at landet, paa den tid den store, gamle Trondhjemsdal blev 

 utformet, stod omkring 300 m. høiere end nu; som vi ser stem- 

 mer dette ganske godt med angivelsen fra British Columbia. Vi 

 skal ikke ved denne anledning fordype os i hypotheser med 

 hensyn til det mulige tidspunkt for denne proces, men vi kan 

 være meget tilfreds med, at det ialfald er lykkedes at fremfinde 

 et karakteristisk træk, der tillater at skimte en forbindelse mel- 

 lem vort omraade og andre, der grænser til samme hav. De bas- 

 siner, vi finder i denne gamle dals bund, og deres beliggenhet 

 viser os imidlertid, at en anden, exogen kraft her, likesom i den 

 nuværende Trondhjemsfjord, har gjort sig i merkbar grad gjel- 

 dende ved siden af de to ovenfor nævnte. 



Som en kraft af den art kjender vi for tiden kun den glaciale, 



