300 Notes Oil the Geology of the Island of Yesso, Japan. 



near Kakumi, and at tlie lead mines of Isliinowatari and Urnp. The 

 rocks at tlie two last-named places are not as much uplifted and metamor- 

 phosed as the granitic and auriferous rocks, but they are probably parts 

 of the same series of formations. The only recognizable fossil found is 

 apparently a fragment of a calamite, leading me to suspect that the beds 

 are of Carboniferous age; but this is by no means certain, and although 

 diligent search Avas madenootlier evidence of the age of these formations 

 could be found. Near Iwanai there are beds of good coking coal in 

 strata that have no lithological resemblance to the auriferous series, 

 but they are uplifted at a high angle. Fossils apparently of Creta- 

 ceous or Jurassic age are found in the eastern part of the island. 



The next stratified formation of interest is marine Tertiary or Post- 

 tertiary, which rests unconformably upon the older stratified beds, 

 and is highly charged in some places with well preserved fossils 

 scarcely distinguishable from the niollusca now existing upon the 

 coasts. In these deposits, and in later terracedike formations, there is 

 abundant evidence of the comparatively recent uplift of the whole 

 island, and the same evidences are found upon the island of Nipon. 



Dynamically, the formation of greatest interest is without doubt 

 the volcanic conglomerate and the associated beds of finer volcanic 

 materials. They record the most energetic volcanic action at an 

 early period before the recent uplift, for it is almost certain that the 

 mass of the conglomerate was deposited under water. It seems as if 

 there had been a series of violent subaqueous eruptions, perhaps at 

 the time the now-existing cones began to be formed. It is most 

 probable that the island has been gradually formed by the rising of 

 these separate cones above the sea, thus giving at first a group of 

 islets, each a volcano, similar perhaps to those which can now be seen 

 off the coast and at the entrance to the Bay of Yeddo. One is repre- 

 sented opposite the western coast on the Japanese maps. 



