CHAPTER 2
GEOLOGICAL CONDITION
Geology of the survey area is depicted on the Regional Geological Map of
Tumbangmanjul Quadrangle, Kalimantan. (U. Margono, T. Soejitno, & T. Santoso, 1995)
scale 1:250.000. The survey area of PT Kapuas Prima Coal is located in the central part
of Regional Geological Map, and lines in Sukadana Granite (Figure 3).
Figure 3. Regional Geological Map of Survey Area and its Surrounding (U. Margono et al, 1995)
2.1 Physiography and Morphology
Indonesia lines in area under confluenced of 2 (two) young mountain system, namely
series the Circum Pacific and Circum Mediterranean series, so they forms many
mountains in Indonesia. In the marine side, Indonesian lies in maritime territory
forming archipelago which is surrounded by three major oceans, namely: the eastern
Chapter 2. Geological Condition
6
part of Indonesia faced to Pacific Ocean, south of Indonesia deal with Indian Ocean,
and the Northern part of Indonesia deal with South China Sea.
According to Van Bemmelen (1949) Kalimantan Island is divided into several
physiographic zones (Figure 4), namely :
Figure 4. Physiographic Map of Kalimantan (Van Bemmelen, 1949)
1. Schwaner Block considered as part of the Sunda plains.
2. Paternoster Block, including Paternoster courtyard now conveniently removable East
Kalimantan and partly in the plains of Borneo known as sub basin.
3. Meratus Graben is located between blocks Schwaner and Paternoster, this area as a
part of the Kutai Basin.
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7
4. Kuching High is a deposition source deposition, the direction is Northwest to
Southeast Kalimantan during the Neogene basins.
5. Tarakan Basin, which is located at the North of East Kalimantan. The north side of
this basin is bounded by "Semporna High".
6. Kutai Basin is located next to the South of Kuching High which is a reservoir of
deposition of Kuching High during the Tertiary. This basin is separated by a tectonic
element known as Paternoster Cross Height of the Barito basin.
Based on the physiographic map of Kalimantan the survey area lies in Schwaner Block
with the morphology can be classified into undulated and highland unit, heights
between 20 - 200 m above sea level (Figure 5). Undulated unit have slope about 5°15°in low area, and highland unit stretching northwest-southeast with slope variations
about 15°- 35°.
Figure 5. Geomorphology of Survey Area
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8
2.2 Stratigraphy
Stratigraphic units that are distributed in the survey area and its surroundings from old
to young (Figure 6), consist of (extracted from the Regional Geology):
Figure 6. Correlation of Map Unit
(Systematic Geological Map, Tumbangmanjul Quadrangle; Scale 1:250.000; U Margono et al,
1995).
GRANIT SUKADANA (Kus): Quartz monzonite, monzogranite, syenogranite, and alkalifeldspar granite; minor quartz syenite, minor quartz syenite, quartz monzogranite and
quartz diorite. This
unit
intrudes
and has
thermally
metamorphosed
Pinoh
Metamorphic and Ketapang Complex; overlying Kerabai Volcanic, intruded by
Sangiang Granite and overlain by Bunga Basalt. The age of the unit is 86.3 to 103 Ma
based on K-Ar method.
KERABAI VOLCANIC ROCK (Kuk): Consists of andesite lava, dacite lava and rhyolite,
welded mostly undifferentiated of pyroclastic rocks (ash, lapilli, crystal and tuff,
volcanic breccia and agglomerate). The unit unconformable overlying on Laur Granite,
intruded by Sangiyang Granite, overlain by Bunga Basalt and partial equivalent of Bunga
Basalt.
2.3 Structural Geology
Most of the Tumbangmanjul Sheet covered by Schwaner Batholith; mainly Cretaceus
granite. Generally faults and joints shows Northwest-Southeast direction in the South
Sheet, and turned to be southwest-northeast in the North Sheet. West-East lineament is
Chapter 2. Geological Condition
9
possibly normal fault. In terms of plate tectonic concept, the Sepauk Tonalite and Laur
granite of Schwanner Batholith were relates to subduction activity to the north of the
area. This concept may be marked by the melanges of the Serabang Complex of West
Serawak and Sambas/Siluas Sheet, and the Boyan mélange in the Sintang Sheet (all of
the outcrop located in the north of the sheet). The existence of dyke swarms (Sintang,
Intrusive, Toms) of Paleocene age within the Schwaner Batholith indicated that, at that
time at least, tension prevailed. The absence of the Tertiary sediment unit indicating
that the area was stable since Cretaceous.
Chapter 2. Geological Condition
10