Formation is contemporaneous with the aforementioned radiolarian chert in the Bantimala Complex Wakita et al.,
1996, although Hasan 1990 reported Late Cretaceous foraminifers from the formation. The equivalent of the
Balangbaru Formation is located in the Barru and Latimo- jong areas of South Sulawesi.
The sandstone of the Balangbaru Formation is composed of quartz, micas, plagioclase and rock fragments of meta-
morphic, shale, and chert. The main provenance for the sandstones of the Balangbaru Formation was the meta-
morphic component of the Bantimala Complex.
The Pitap Formation consists mainly of flysch-type sedi- mentary rocks such as sandstone, siltstone, conglomerate
and shale with subsidiary limestone layers and blocks which contains the foraminifera Orbitolina cf. oculata of
Aptian–Albian age Sikumbang and Heryanto, 1994.
The Pitap Formation of the Meratus Complex and the Barangbaru Formation of the Bantimala Complex were
deposited in a forearc basin. The Selangkai Group of West Kalimantan is equivalent to the Pitap and Barangbaru
Formation. The forearc sedimentary units in West and South Kalimantan and South Sulawesi were accumulated
contemporaneously as terrestrial deposits in the wide region of the forearc basin Fig. 3.
5. Volcanic arc unit
5.1. Late Cretaceous volcanic suite An andesitic to basic volcanic unit is present in South
Kalimantan Figs. 2 and 3, and similar rocks are inferred as a provenance of the sandstones of the Luk Ulo Complex.
The Haruyan Formation in the Meratus area, South Kali- mantan is a product of Late Cretaceous volcanic activity
Heryanto and Sanyoto, 1994; Heryanto et al., 1994. The Haruyan Formation consists mainly of basic to andesitic
volcanic rocks, such as lava, tuff and tuff breccia. The lavas sometimes show pillow structures indicating submarine
volcanism Wakita et al., 1998. Tuff breccia consists of feld- spar phenocrysts, pumice, lava fragments and irregular-
shaped fragments of pale-colored chert within a light purple colored tuff matrix. One of the chert samples has yielded
Cenomanian radiolarians. The Haruyan Formation is interfin- gered with the Pitap Formation which was deposited in a fore-
arc basin Haryanto and Sanyoto, 1994; Heryanto et al., 1994.
Andesitic volcanic activity, represented by the Haruyan Formation of the Meratus Complex may be partly contem-
poraneous with the felsic volcanic activity recorded by the rhyolite within the chert beds of the Bantimala Complex.
The andesitic volcanic rocks of the Haruyan Formation are a possible provenance of andesitic volcanic fragments in the
sandstone of the Luk Ulo Complex.
Petrography of sandstones in the Luk Ulo Complex suggest that the provenance was an immature volcanic arc
Wakita et al., 1998. The sandstone is lithic wacke composed mainly of angular to subrounded fragments of
feldspars and rock fragments of intermediate to basic volca- nic rocks. This suggests that the most important provenance
of the sandstone was a volcanic terrain of intermediate to basic composition.
5.2. Cretaceous intrusive rocks Leucocratic rocks, classified as “plagiogranite”, occur in
the Meratus Complex closely associated with ultramafic rocks Sikumbang, 1986. Granite and granodiorite have
also been recorded from a few localities in the Meratus Mountains Sikumbang and Heryanto, 1994. Granodiorite
is intruded into the Pitap Formation. K–Ar dating of the granite yields an age of 115 Ma Heryanto et al., 1994.
The granitic rocks are possibly products of Late Cretaceous volcanic activity in an immature volcanic arc located in the
Meratus area.
5.3. Ophiolitic unit Ophiolite units are recognized in the Luk Ulo, Bantimala,
Meratus, Ciletuh, Jiwo, Barru, Latimojong and Sangkuriang areas Figs. 2 and 3. They represent obducted oceanic plate
and are dismembered by tectonic disruption. They occur as tectonic blocks, consisting mainly of altered ultramafic
rocks, associated with pillow lava and chert.
Dismembered ophiolite crops out in the Karangsambung area of Central Java. It occurs as a tectonic block which is
elongated more than 10 km in an E–W direction with 2 km thickness in N–S direction. It is separated from melange and
schists by faults. The ophiolite consists of pillow basalt, dolerite, gabbro, serpentinized peridotite and lherzolite;
these rocks have suffered zeolite to greenschist facies meta- morphism Suparka, 1988.
Ultramafic rocks of the Bantimala Complex, South Sula- wesi are dark green in color, and mostly serpentinized peri-
dotite, with local chromite lenses. The age of the ultramafic rocks is unknown. Two massifs of sheared, faulted and
variably serpentinized ultramafic rocks crop out extensively in the Meratus Complex, South Kalimantan. They are called
the Meratus and Bobaris ophiolites. They comprise serpen- tinized peridotite, harzburgite and dunite with minor pyrox-
enite, and are intimately associated with gabbro and amphibolite. The ultramafic rocks are variably affected by
low-grade metamorphism. Chromite is sometimes present but is a minor constituent.
No age data is available for the ultramafic rocks and pillow basalt in the three complexes. If the rocks originated
from the oceanic plate or seamounts born near ridges, their ages would be older than the age of the radiolarian chert
Fig. 3.
6. Overlap assemblage
