In this survey, the vole. Sambe has been ascertained to burst into eruption 6 times from 3×10⁴y. till 3×10³y. During the 1st period, pumice fall (K1), pumice flow (K2) and pumice fall (K3) were blown off. K1 covered pumice bed (DK) produced in the volc, Daisen -30200 ± 3500 y. B. P. - around Yokota. K3 streamed N. E. E. no less than 75 km. and covered DK around Matsue. During the 2nd period, ash (O1), pumice flow (O2) - 25600 ±1000 y.B. P. - and ash (O3) were erupted. Mass of O2 is supposed to be 100 km³. 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 TiO2/T. Fe≒0.02〜00.3 and biotite is exceedingly much. During the 3rd Period, the vole. Sambe blew off ash (I1) and pumice (I2). I_2 contains special pisolite and shows TiO2/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: TiO2/T. Fe≒0.052, biotite is more in the upper layer; TiO2/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 (U2) and ash (U3) off. U2 shows TiO2/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 (S1), pyroclastic flow (S2) - 4480±110 y.B. P.-, ash (S3), and pyroclastic flow (S4, S5), 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 (T0), 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 (B1)- 4910±120 y.B. P. - is just under S1 and B"2 -3680±90 y. B.P.- is just under T0. The former can be regarded to be ejected in the beginning of the 5th, the latter in the beginning of the 6th Period. B3 is just under Tn and has no continuity. B4 covers Tn and crops out. Concerning the pyroclastics of the vole. Sambe from the 4th to the 6th Period, TiO2/T.Fe scarcely stands for different value. As the value of TiO2/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.

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Correlation of the stratigraphic sections of the Tama Loam (tephra), by key beds of pumice layers, at some hills in South Kanto leads to some conclusions as the following. 1. The thickness of the Tama Loam totals about 40m, and it corresponds to that of all the loam units-Suarashi, Shimosueyoshi, Musashino and Tachikawa loams-younger than the socalled Tama Loam. The lower part of the Tama Loam unit is characterized by intercalations of dacitic pumices, whereas the upper part by andesitic pumices. 2. Such unconformable features as to be found near the boundary between Shimosueyoshi and Musashino loams are also found at two horizons within the Tama Loam. 3. From the facts mentioned above, the length of time through which the whole strata of the Tama Loam were deposited, may be inferred as being enough long to cover, for instance, whole time length implied by known several tephra units younger than the Tama Loam. Furthermore, the stratigraphic value of the Tama Loam may be on a par with that of the group including all the loam units younger than the Tama Loam. 4. The so-called Tama topographic surfaces which carries the Tama Loam upon them are tephrostratigraphically classified at least to four levels of terrace namely, from older to younger, the Sayama, Hodokubo, Kobiki and Oshinuma terraces.

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The Koyama Gabbro mass intruding into the Miocene sedimentary strata has various kinds of rock facies such as anorthosite, anorthositic gabbro, gabbro, diorite, aplitic granite and aplite. The Sr;87/Sr86 ratios for each rock facies including apiitic granit and aplite are well constant, and the average ratio (0.706) is slightly higher than that for Japanese basaltic rocks. This result indicates that it is unlikely that the aplitic rock was formed through assimilation of an appreciable amount of sialic crustal material relatively rich in Sr87.

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