No. 4.] CHAL3IERS — SURFACE GEOLOGY. 206 



In reojard to the conditions of the formation of the Baie de 

 Chaleur Leda clays, it may be stated that at whatever depth of 

 the sea the lower clay was deposited (and it appears probable 

 that it was laid down in waters not deeper than the Baie de 

 Chaleur is at the present day, namely 20 to 30 fathoms), the 

 hie:her strata bear evidence of havina; been formed in shallow 

 waters. For, not only has the upper surface of the clay been 

 eroded and channelled by currents previous to the deposition of 

 the marine sands, but the fossil shell themselves in many casei 

 indicate that they were washed about by the sea and thrown 

 together in masses, occurring often compacted two or three 

 inches deep with the valves mostly separated and broken. Occa- 

 sionally, too, they seem to occupy pockets or holes in the upper 

 part of the clay, and are heaped up sometimes on one side or the 

 other of the larger boulders. The frequent conmingling of deep 

 water and littoral species may thus be accounted for, the sea 

 having washed those from shallower waters into greater depths, 

 and vice versa. 



But although the assemblage of shells embraced in the fore- 

 going list does not afford conclusive testimony as to the depth of 

 the sea in the Post-Pliocene period, yet it is of value as showing 

 that the climate and the waters of the Baie de Chaleur reiiion were 



O 



much colder then than now. The shells imply, indeed, a tempera- 

 ture boreal or subarctic in charater, similar to that of Labrador 

 or the south of Greenland at the present day ; nearly all the 

 species mentioned being now found in the seas adjoining these 

 countries at moderate depths. Their occurrence at the Baie de 

 Chaleur may be explained by supposing that the land stood 100 

 to 150 feet below its present level, thus allowing the cold waters 

 of the arctic current to circulate freely in the southern part of 

 the Gulf and tenant it with such species as are now found only 

 in extreme northern latitudes. But the fact that the fossils are 

 met with chiefly in the beds which have accumulated at or near 

 the mouths of rivers would lead us to infer that the cold fresh 

 waters which must have poured into the bay in great quantities 

 during the time of their existence have had a greater or less 

 effect upon them ; and their irregular forms, the strength and 

 thickness of the shells, as well as their abundance are probably 

 due to that and other local causes. The purely arctic fauna of 

 the lower Leda clay may have lived in the Baie de Chaleur 

 before the final retreat of the glaciers. 



