18 



University of California Publications in Geology [Vol. 10 



so long applied to them, and which was adopted by the International 

 Committee 24 some years ago. If the name be retained for the rocks, as 

 nearly all geologists conversant with this field are agreed, it seems 

 proper and convenient to use the same term for the time-division in 

 which they were formed. The second division of the lapse between the 

 Ontarian and the Huronian is recorded in terms of erosion only. We 

 have no rocks to discuss or to name. But to complete the time-scale 

 and so keep our ideas on the subdivision of geological time clear, it is 

 desirable that we should name this period, and I have in a former 

 paper suggested that it be designated the Epilaurentian Interval. 25 



Similarly the Huronian is separated from the Algonkian by the 

 time necessary for the development of the Algoman granite, with its 

 concomitant diastrophism, and by the succeeding period in which the 

 region was reduced to a surface of low relief. These time-divisions I 

 have designated the Algoman 20 and the Eparchean Interval. 27 The 

 last-mentioned term is much preferable to Epalgomian suggested by 

 Schuchert 2S as a substitute for the earlier name, because the interval 

 separates the great Archean Era from the Paleozoic. There can be no 

 doubt that historically the Huronian is a subdivision of the Archean, 

 and its relations to the Algoman are so similar to the relations of the 

 Ontarian to the Laurentian, that it is most appropriate to group this 

 dual set of relations and geological conditions together under the com- 

 prehensive term Archean. In this sense the term designates an era 

 of time truly and characteristically archaic, even from a geological 

 point of view. The general plan of continental growth in Paleozoic 

 time is usually regarded as having been inaugurated with the Cam- 

 brian, but in fact it began with the Animikian. At the close of the 

 Eparchean Interval the vast continental platform, upon which the 

 Paleozoic rocks rest, had been completed. The early Cambrian conti- 

 nent of Walcott 28 was but a slightly modified phase of the continent 

 upon which the Animikian strata were deposited. It was Animikian 

 sedimentation that ushered in the Paleozoic Era. Previous to the 

 Eparchean Interval the physiography of the continent had been 

 wholly different, and its growth had proceeded on other lines. Events 



24 Journ. Geol., vol. 13, 1905. 



25 A Standard Scale for the pre-Cambrian rocks of North America, Cong, 

 geol. internat., XII, 1913. 



26 Cong. geol. internat. XII, 1913. 



27 Bull. Dept. Geol. Univ. Calif., vol. 3, no. 3, 1902. 



28 Text-book of Geology, p. 445, 1915. 



2» U. S. G. S. 12th Ann. Rpt., 1, 1890-91. 



