三瓶火山の噴出物と層序
スポンサーリンク
概要
- 論文の詳細を見る
In this survey, the vole. Sambe has been ascertained to burst into eruption 6 times from 3×10^4y. till 3×10^3y. During the 1st period, pumice fall (K_1), pumice flow (K_2) and pumice fall (K_3) were blown off. K_1 covered pumice bed (DK) produced in the volc, Daisen -30200 ± 3500 y. B. P. - around Yokota. K_3 streamed N. E. E. no less than 75 km. and covered DK around Matsue. During the 2nd period, ash (O_1), pumice flow (O_2) - 25600 ±1000 y.B. P. - and ash (O_3) were erupted. Mass of O_2 is supposed to be 100 km^3. According to this burst, a caldera of 4km. in diameter was formed. The ferromagnetic minerals in the pyroclastics through the periods of the 1st and the 2nd shows TiO_2/T. Fe≒0.02〜00.3 and biotite is exceedingly much. During the 3rd Period, the vole. Sambe blew off ash (I_1) and pumice (I_2). I_2 contains special pisolite and shows TiO_2/T. Fe≒0.072. The consequence of this action can be seen as far as 55 km. S. E. E. and in the distant places, the data about this pumice are following: TiO_2/T. Fe≒0.052, biotite is more in the upper layer; TiO_2/T. Fe≒0.070, hornblende is more in the lower layer. During the 4th Period, after the vole. Sambe blew off lava (HL) which made Hikageyama lava dome, it also blew pyroclastic flow (Uj) - 16000±400 y. B.P. -, pumice fall (U_2) and ash (U_3) off. U_2 shows TiO_2/T. Fe ≒ 0.086 and contains hornblende much. The pumice bed of 15 cm. thick can be seen at a distance of 65 km. S. E. E. During the 5th Period, after blowning off ash (S_1), pyroclastic flow (S_2) - 4480±110 y.B. P.-, ash (S_3), and pyroclastic flow (S_4, S_5), the vole. Sambe ejected lava (SL) which made Sambe lava domes. The petrological difference between SL and HL cannot be distinguished and both are composed of rhombic-pyroxene bearing biotite-hornblende dacite. During the 6th Period, ash (T_0), more than five layers of pyroclastic flow (Tfw) and the newest ash (Tn) were ejected. Tfw, after filling the southern half of the caldera with itself, flew down along the river Hayami. There are four layers of black humus around vole. Sambe. The oldest one (B_1)- 4910±120 y.B. P. - is just under S_1 and B"2 -3680±90 y. B.P.- is just under T_0. The former can be regarded to be ejected in the beginning of the 5th, the latter in the beginning of the 6th Period. B_3 is just under Tn and has no continuity. B_4 covers Tn and crops out. Concerning the pyroclastics of the vole. Sambe from the 4th to the 6th Period, TiO_2/T.Fe scarcely stands for different value. As the value of TiO_2/T. Fe in the pyroclastics of the vole. Daisen is more than 0.11, the pyroclastics of the vole. Daisen are obviously discriminated from those of vole, Sambe.
- 地学団体研究会の論文
- 1971-07-25