Page 79 - Sumatra Geology, Resources and Tectonic Evolution

66 CHAPTER 6

Table 6.2. Palaeozoic volcanic units in the West Sumatra Block
Formation Unit with volcanies Age Description Reference
Kluet Probable Carboniferous-Early Green metavolcanics in phyllites in Cameron et al. (1983)
Permian the upper Jambo Aye and green
metatuffs in the upper Serbajadi
river among conglomeratic
metawackes, metaquartzites,
metalimestones, phyllites and
arenites
Porphyritic matic metavolcanics Cameron et al. (1982b)
associated with metasediments in
the Kr. Rancah (?2936 3939).
Hippogriffe rocks Carboniferous-Early Permian Diabase Verbeek (1897)
Kuantan Local Phyllites and schistose metatuffs Rock et al. (1983)
Phyllite and Shale Member Flows of andesite and basalt among Silitonga & Kastowo (1975)
quartzites and quartz sandstones
Lower Member Vis~an Intercalations of volcanic rock and
chloritised tuff within quartzites,
sandstones and shales

The metatuffs mapped by Rock et al. (1983) and the diabase East Sumatra Plutonic-Volcanic Belt
(Verbeek 1897) forming the Hippogriffe rocks, an islet south of (Permian volcanism)
P. Bangka in the Java Sea (Fig. 6.1) also may be included in
this episode. The younger episode of Kuantan Volcanism has The East Sumatra Plutonic-Volcanic Belt, the 'Permian mag-
not been dated, but is post-Vis~an, and may be of Permian age matic arc' of Katili (1973), was defined on the basis of Rb-Sr
(see later). age determinations on feldspars obtained from cores drilled
The green metavolcanics noted by Cameron et al. (1982a) in the in the concealed Setiti batholith (Setiti-4, brecciated granite,
Alas Formation in the Medan Quadrangle may be of Vis6an age, 298 + 30Ma and Setiti-5, sheared granite, 276 ___ 10Ma).
like the associated limestones, while metavolcanic localities in Suwarna et al. (1991) suggest that the volcanic Condong
the Kluet Formation in the north of Sumatra have not been Member of the Mentulu Formation (Table 6.3) in the nearby
accurately dated, but may be of Carboniferous or Permian age. Tigahpuluh Mountains (Simandjuntak et al. 1991) is also of

System Stage WEST SUMATRA BLOCK EAST SUMATRA BLOCK INDOCHINA BLOCK

Changsingian ?
uJ
9 ~ Wuchiapingian I I I 9 l 1
I
i
!
_J tl [ l l l l l l [ l l i I I I Kaloi,
Capitanian 9 I I 9 I I ! ~
II,l~',~]J~
~L Batumilmil Formations
....... II I i 1 i I
- r -r "-i--r r I Guguk Bulat I I I I I I
I I I I I I l l ! I l l ! I l l
Wordian I l i I I I I l l l l l l l l l
Bukit Pendopo
| i 9 9 9 ?
._1
Roadian
m Basalt
13_ Kungurian ~ Calcareous Member %, ~ "% "X. "*,. Riau-Billiton
Accretionary
Kluet Formation Complex
..........
......
>5, Artinskian f,,...., it VolcanicMember Basalt (shales,siltstone
~i iii~ i~ii ~i~ (Palepat Formation) basalt and
<~ Sakmarian Condong Member I% % %-. % ~'%N serpentinite)
~.J,
k. ", _%2"~
ILl fi!~i~i~i~i!~i~i:!l Mengkarang Formation 'Pebbly mudstone'
Asselian ? Bohorok and Metulu
Gzhelian Pengabuhan N Formations
Formation
O0 Kusimovian ......... Gangsal Formation
8 Muscovian 9
....... ,
C
Bashkirian o
ii
Serpukovian
............... ,9
Visean g Limestone Member Alas Formation
iL:!~-!~ !:!i Lower Member
Tournaisian
,.t
Fig. 6.3. Simplified composite Carboniferous and Permian stratigraphies of the East and West Sumatra Blocks and the Indonesian islands in the Indochina Block.