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The Northwest Borneo geosyncline in its geotectonic setting
No full textThe Cretaceous-Cenozoic Northwest Borneo Geosyncline shows many
similarities with the geosynclinal couple described by Auboin (1965). Previous
syntheses have assumed that the foreland of the geosyncline was the so-called
"Continental Core" of west Kalimantan lying to the south, but it is here suggested
that the "Continental Core" did not act as a foreland, but as a eugeanticlinal
ridge and intermediate hinterland. Thus the internal zones of the geosyncline
lay to the south. The main eugeosynclinal furrow occupied the present outcrop
of the Rajang Group whereas the later miogeosynclinal furrow lay further northa submerged miogeanticlinal ridge, not so clearly defined, separated the furrows.
The Plateau Group, part of the Nyalau Formation, and the Brunei Group
represent post-orogenic molasse-type deposits. The position of the "foreland"
in this pattern would be to the north, in the region of the present South China
Seaand this area may have acted as a tiefcraton (in the sense of Stille), taking
the place of the normal continental foreland.
A marked dynamic polarity is shown by migration of flysch deposition,
orogeny, and molasse deposition, from south to north across the geosynclinethese processes also seem to have migrated along the geosyncline from west
to east and northeast.
The distribution of the main ophiolite-chert belt along the internal side of
the eugeosynclinal furrow, and of the late-geosynclinal and post-geosynclinal lavas
and acid intrusions in west Sarawak and west Kalimantan follows the typical
pattern. A terminal volcanic phase is represented by extrusion of late Cenozoic
lavas over the eugeosynclinal deposits.
DISCUSSION: Discussion centered around the nature and age of the
\u27continental core\u27, the sources of sediment for the geosyncline, and the structure
and in-filling of the deep portions of the geosyncline.
B. N. Koopmans asked whether the apparent polarity, younging to the north,
might not be due to structure and not original depositionthat is, that the
younger flysch to the north could be underlain by Cretaceous flysch. The
speaker replied that this seemed unlikely when the grea
The effects of Late Tertiary and Quaternary tectonic movements on the geomorphological evolution of Brunei and adjacent parts of Sarawak
No full textQuaternary folding, faulting and tilting movements combined with probable
compaction of thick, geologically young sedimentary rocks have fundamentally
controlled the geomorphological evolution of Brunei and adjacent parts of Sarawak.
Areas underlain by anticlinal structures have been up-arched, raised beaches of
probable late Mid-Pleistocene age have been faulted and tilted, and drainage has
been affected by recent downwarping
Glaciation of Mount Kinabalu
No full textMount Kinabalu (13,455\u27) in Sabah, the highest point in the Sunda area,
is comparable in height to other tropical mountains which were glaciated in
Pleistocene. Kinabalu has been referred to as glaciated by Bowman (1916) and
Bowen and Wright (1957). but no description of its glacial features has appeared.
Examination of the bare granodiorite summit area of the mountain (above
about 11,000\u27) reveals convincing evidence of geologically recent glacial action.
The general morphology of the summit area includes smooth. abraded, debrisfree
slopes and bowlssteep. craggy peaks and pinnaclesand some U-shaped
passages leading off the summit between peaks. These features terminate. often
abruptly. at elevations around 12,000\u27. Ice-produced surficial markings and
small-scale features are preserved locally on the abraded summit surface. These
include glacial polish. concentric cracks. concentric gouges. plucking cracks, and
rectilinear glacial grooves.
The general summit morphology argues for considerable glacial erosion on
Mount Kinabalu. while the poor preservation of glacial markings and the rarity
of probable morainal material suggest only mild or fleeting glaciation. A solution
to this apparent contradiction may be the possibility that Kinabalu has been
glaciated more than once during the Pleistocene. and that most glacial erosion
occurred before the most recent (Wisconsin?) period of ice cover
The Tembeling Formation-a litho-stratigraphic description (West Malaysia)
No full textThe name "Tembeling Formation" is introduced for fluviatile-deltaiclacustrine
sediments of post-orogenic origin in West Malaysia (Malaya). A type
section is described in the Tekai River (Pahang), where the total thickness of the
formation is over 3,000 meters. The age of the formation is probably late Triassic
to Jurassic. A basal member, the "Murau Conglomerate", is described from the
Mersing area (Johore)it consists of coarse red purple polymict conglomerates of
fluviatile origin. These conglomerates decrease in thickness from east to west and
vary in composition. The Murau Conglomerate is overlain in the Tahan Range
by a sequence of red to grey shales and mudstones alternating with thick bands
of arenaceous-rudaceous rocks. The top of the formation is formed by typical
argillaceous red-beds, deposited under warm continental conditions. The Tembeling
Formation overlies rocks of varied composition and age. An angular unconformity
well developed in the east of the Peninsula decreases in importance westward.
Along the east coast in the State of J ohore, the formation unconformably overlies
metasediments of probable Carboniferous age, whereas to the northwest in the type
area in central Pahang Triassic rocks are underlying. The folded Tembeling
Formation is unconformably overlain by flat-lying beds of the late Jurassic to early
Cretaceous Gagau Group
Physical and chemical differentiation of West Malaysian limestone formations
No full textA large and representative collection of specimens from each of the
Malayan limestone formations was analysed chemically, mineralogically and petrographically
in an attempt to find a criterion for differentiation independent of
palaeontology. Limited success has been obtained only where the limestones are
sufficiently far removed from granitic intrusions-in Perlis and Kedah, where
significant lithological differences occur between limestones of different formations.
Unfortunately the results cannot be extended to other areas and no generally
applicable criterion for differentiation has been found.
Extensive studies of the thermoluminescence of limestones show that all collected
specimens have been recrystallised during the revolutionary phase of the Thai-Malayan
orogeny so that thermoluminescence cannot be used in Malaya to differentiate
limestones stratigraphically.
It must therefore be concluded that the differentiation of Malayan limestones
must continue to be based on fossils
Upper Palaeozoic stratigraphy of the area west of Kampar, Perak
No full textThe marine sedimentary rocks of the Kampar area, estimated to be
more than 5,500 ft thick, can be lithologically divided into six units, which have
been dated by means of fossils. These units, with their thicknesses and ages, are
as follows (starting with the oldest): Kim Loong No. 1 beds (4,150+ ft, pre-Middle
Devonian)Thye On beds (450 ft, Middle Devonian)Kuan On beds (60 ft,
Carboniferous)Kim Loong No. 3 beds (330 ft, Lower Permian or Upper Carboniferous?)Nam Loong beds (500 ft, Lower Permian)H. S. Lee beds (50+ ft,
Lower to Middle Permian).
The Kim Loong No. 1 beds consist predominantly of dolomites and calcitic
dolomites and are distinguished in the field from the grey crystalline calcitic limestones
of the Thye On beds. The Thye On beds contain Stringocephalus perakensis
Gobbett and are Givetian in age.
The Kuan On beds are characterised by oolitic limestones interbedded with
laminated black shaly limestones and calcitic limestones. Gastropods mainly of the
family Sinuopeidae? are present in the shaly limestones.
The Kim Loong No. 3 beds are composed mainly of unfossiliferous sandstones,
black pyritiferous shales and shaly sandstones.
The base of the Nam Loong beds consists of massive crinoidal limestone.
Overlying this are impure limestones rich in Lower Permian brachiopods.
The H. S. Lee beds are formed of pale limestones. The lower part is Pseudofusulina
limestone and the upper part is unbedded reef limestone with Misellina sp.
and a rich molluscan fauna