THE AKCH.îi:AX FOlîMATlOX OF THE aBUKUMA PLATEAU. gOl 



between the base of the riozai^fho rocks and the Laurentian. The 

 pre.sent paper is tlie fii'st attempt that has ever been made to classify 

 tlie oldest rocks witliin the confines of the Japanese islands. Beina* 

 unable to correlate the series of the upper division with anv 

 with which 1 am ac<piainted in tlie geoloii'y of China and Corea. I 

 propose now to name the tirst yr(jnp tlie (rozaisJio series,^ the second 

 the Tahuiuki aeries.' In the (/>) lower division distinctions of stratigra- 

 pliical sequence and relationship, if any such ever existed, liave 

 been obliterated. For this assembhiL;-e of rocks, viz., the Icnver division 

 of the Archaean, the welld^nown term LaurentidHj so named from the 

 Laurentian Mountains in Canada, and not from the iSt. Lawrence 

 River, is retained. 



The leadinçc divisions of the Arcluean for this rei>"i(jn mav, from 

 what has been stated, be arranged in the following scheme, according 

 to the order of whi<'h the o'eolo^'ical features of the region will be 

 considered in detail : — 



iUpiier dirision. "■• (tozaisho series. — (Iluronian?) 



Archiüan \ i-i. Takanuki series. 



\ljinrer Airh'wn. — Laurentian, 



A more comprehensive statement of the results arrived at, 

 will be given in the summary, after the facts, upon which these 

 and other generalizations are based, luive been set forth. 



IV. Straligraphicai Relations and Slructure^ 

 Sections. 



Having sketched briefly the genend aspect of the plateau, and 

 pointed out my aim, I mav n(jw consider the stratigra[)hical com- 

 position of the series. It was fjund thtit it is usually disposed in 



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