UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 Bulletin of the Department of Geology 



Vol. 3, No. 3, pp. 51=62. ANDREW C. LAWSON, Editor 



THE 



EPARCELZEAN INTERVAL 



A CRITICISM OF THE USE OF THE TERM ALGONKIAN 



BY 



Andrew C. Lawson 



In the year 1854 Logan proposed the name Laurentian for a 

 series of rocks, which he and his assistants on the Geological 

 Survey of Canada had been studying for the preceding nine 

 years in the region of the St. Lawrence and Ottawa rivers. He 

 had in earlier reports referred to the same rocks as the "meta- 

 morphic series," and had shown conclusively that a part of them 

 at least, comprising limestones, quartzites and conglomerates, 

 were clastic rocks. In subsequent reports, and especially in the 

 summary report of 1863, the term became very much extended, 

 and vast terranes of granite-gneisses, anorthosites, etc., were 

 included under it, as well as more evenly banded or bedded 

 gneisses. By reason of their association with the recognizably 

 clastic rocks, these granite- gneisses, anorthosites and banded 

 gueisses were regarded as also of metamorphic derivation from 

 original clastic sediments, and various attempts were made to 

 treat them stratigraphically. With the progress of exploration 

 it became apparent that this vast complex was resolvable into 

 three subdivisions, and these became known as the Lower, 

 Middle and Upper Laurentian, the first consisting of granite- 

 gneiss, the second of limestones, quartzites, conglomerates and 

 banded gneiss, and the third of anorthosites. These subdivisions 



